Drive shaft balance

[Paul G]

Vibration issues at highway speeds can be a real problem to find. I have already corrected many issues that were causing the vibration. Still trying to get the last bit of it handled.

Vibration can be felt in the floor along with an oscilating sound. It starts around 65 mph on up in speed. The car will only do 130mph. Vibrates from 65 on up.

Pinion angle issues have been sorted. Pinion angles are about 2° between the drive shaft and diff pinion and also 2° between the drive shaft and trans yoke. Tranny has a downward angle, diff pinion has an upward angle, the drive shaft is running downhill to the diff. Trans is as high up, and centered in the tunnel as it can get. It is an A518 although the 727 had vibration issues as well. I have recently added a 2 1/2° degree shim under the axle adding some downward angle to the diff pinion, that did not make any difference in the vibration.

Tires have been balanced twice. Made no difference. I have inspected wheel run out visually with the axle on jacks and wheels spinning. Visually they are straight. Do I need to be more accurate that that? Any ways I have read that wheel issues will come and go at certain speeds. Not my situation. Vibs come in at 65mph and stay.

For the drive shaft, When I did the A518 swap the shaft had to be shortened. The shop that cut it told me it was bent and out of balance. The straightened it and balanced it. All back together and still had vibration issues. After some time passed I pulled the shaft back out and took it to another shop. They said it was straight but out of balance and needed new U-joints. Got it done, put it back in, vibs seemed to be better at first but not completely gone.

Each time the drive shaft was back in the car after a balance it felt like it was smooth but only for the first few miles. Then again something like that is hard to tell if it is real, or just me not paying attention. It feels like the vibs are getting worse as time goes on. So to my question. Is it possible that a drive shaft for some reason may be prone to going out of balance? I am not easy on this Charger. It was a Grandma's car, aint no more. It likes doing burn outs and spirited driving.   

I don't want to throw any more $$ in to a drive shaft that wont stay balanced, if that is possible.
 

[ws23rt]

The best clues you have are that when the drive shaft comes back from the shop it seem ok at first.

That you test the shaft with your engine torque rather hard from time to time is another clue.

Maybe it is time to get a good one (heavy tube size etc.)  Also some drive shaft shops are better that others.
Since I did not sort through your pinion angle information I won't comment on that.
BTW once a straight and true tube has been bent and straightened again it no longer has an even stress along it's length. It is no longer as good as it was new.

[cudaken]

Vibration can be felt in the floor along with an oscilating sound. It starts around 65 mph on up in speed.

Paul does it still have the oscillating sound and feel?

Do you have air shocks by chances? If you do try changing the air pressure, it will change the rear end angle. If it changes at what speed the oscillating is happen at, then something is still off far as drive-shaft angles goes.

Tranny has a downward angle, diff pinion has an upward angle, the drive shaft is running downhill to the diff.    

To be honest Paul, I have no idea if the tail shaft should be pointing at a up, center or at downward angle? But I have read you had the same problem with the 727, by chances did you use the same transmission mount?

The car will only do 130mph

There the Problem! The Charger Is Scared

True story. I had a little old lady come in when I was working at NTB. She told me her Ford Escort started shaking at 85 MPH? (she was in her mid 60's) She asked me why was it shaking? I told her Because it is Scared! 

Well the last part is not helpful but true. 

Cuda Ken

[Big Sugar]

Im suffering the same issue, used to have a tremendous vibration above 65 that kept me out of the throttle seemed to come in earlier under hard acceleration . Rebalanced the tires and rims all round replaced both U joints installed a new bushing in the 727 tailstock, new trans mount reshimmed the rear end to set the pinion 2* lower and the vibration moved up to 75 mph, its not as dramatic but it still occilates and sometime shows up ea little earlier under hard throttle,
I think im gonna swap out my driveshaft for a new one and get a new tailshaft as i suspect the shaft may be a little too loose in the bushing.

Ron

[Paul G]

Vibration can be felt in the floor along with an oscilating sound. It starts around 65 mph on up in speed.

Paul does it still have the oscillating sound and feel?

Do you have air shocks by chances? If you do try changing the air pressure, it will change the rear end angle. If it changes at what speed the oscillating is happen at, then something is still off far as drive-shaft angles goes.

No air shocks. It has pretty stiff leaf springs that set the rear up a bit from stock.

Tranny has a downward angle, diff pinion has an upward angle, the drive shaft is running downhill to the diff.  

To be honest Paul, I have no idea if the tail shaft should be pointing at a up, center or at downward angle? But I have read you had the same problem with the 727, by chances did you use the same transmission mount?

The A518 requires a totally different mount position on the trans. Stock mount was cut off the cross member, used a flat type mount on a fabricated plate welded to the cross member to get the mount in the new position for the A518.

The car will only do 130mph

There the Problem! The Charger Is Scared

True story. I had a little old lady come in when I was working at NTB. She told me her Ford Escort started shaking at 85 MPH? (she was in her mid 60's) She asked me why was it shaking? I told her Because it is Scared!  

Well the last part is not helpful but true.  

Cuda Ken

Just wondering if any one else has had a DS that would not stay in balance. It just may be time to call Denny's.

[fy469rtse]

Bet the rear bush is now needing to be changed out when you put that new drive shaft in, try dts as well , go thick wall ? Are you using the large universals 7290 big block , pay attention to the universals you use , get the best , no point skimping on this area

[ottawamerc]

Ok if someone finds the solution to this it HAS to become a sticky On my drive home last nite from Moparfest getting the soothing vibration from my car I got to thinking, is it possible that we are just used to our new rides being smoother and 40+ yrs ago this type of vibration was the norm?

Scott

[Big Sugar]

No im pretty sure we're missing somthing, it is definatly a driveline related issue i just wonder if its a flex plate or convertor issue. Trouble i it definatly sounds like its right between the seats, seems like its a harmonic issue in the driveshaft. May have to replace the driveshaft.


Ron

[ws23rt]

No im pretty sure we're missing somthing, it is definatly a driveline related issue i just wonder if its a flex plate or convertor issue. Trouble i it definatly sounds like its right between the seats, seems like its a harmonic issue in the driveshaft. May have to replace the driveshaft.


Ron

The clues you have do point to the driveshaft. Especially that it is aggravated by adding throttle. It would change the pinion angle some under load.

It seems less likely to be flex plate or convertor because one would expect it to show up in a lower gear/lower speed. (rpm related).

[ottawamerc]

Hey Ron don't bother with the converter flexplate or drive shaft I already tried that in desperation and it didn't fix it! As for my earlier comment on the good vibrations being the norm I was definay wrong cause the tail shaft leaked a lot of oil out ! It's gotta be the pinion angle

Scott

[flyinlow]

Does it vibrate the same above 65mph in third as it does in OD?  Does being in lock up mater to the vibration?

[Dodge Don]

Hard to tell what is "normal". Typically I avoid the highways like the plague because of my 3.91 gears but the drive home from Moparfest required a run on the 401. When I'm on the highway I usually try to keep it around 3500 RPM which is around 55 MPH for me (everyone passes me like I'm standing still  )....I get a rythmic ocilation...more of a drone.....hard to explain.....car feels fine, runs great but you get the mmmmMMMMMmmmmmmMMMMMMmmmmm sound. I was thinking of swapping in an aluminum driveshaft to shed a few pounds, reduce the rotating mass and get a more balanced shaft? 

[MSRacing89]

Don't want throw a wrench into the mix here but a rhythmic vibration especially at a certain RPM is a lot of times related to the Harmonic Balancer. 

Does it oscilate if you are sitting in the driveway with no load at a that RPM?

[Dodge Don]

Don't want throw a wrench into the mix here but a rhythmic vibration especially at a certain RPM is a lot of times related to the Harmonic Balancer. 

Does it oscilate if you are sitting in the driveway with no load at a that RPM?

Not for me.

[1BAD68]

I get the same oscillating vibration. Starts around 60-65 thru about 85mph where it just sort of goes away.
Sounds like going over a series of rumble strips but not as loud.
Definitely not tires or transmission as I changed both with no changes.

[Dodge Don]

Kind of like the drone sound you hear on old WW2 movies from inside a bomber on it's way to drop its load

[john108]

This may not be applicable but: I had a problem once where I had a lot of vibration at lower to medium speeds but when at highway speeds, it smoothed out.  The problem turned out to be the U-Joints.  Some Rollers had fallen out of the bearings.

[Paul G]

I get a rythmic ocilation...more of a drone.....hard to explain.....car feels fine, runs great but you get the mmmmMMMMMmmmmmmMMMMMMmmmmm sound.   

That is the sound. It was much more noticeable and came in at a slower speed until I got the pinion angles aligned better. Make sure your tranny is centered in the tunnel. Pinion alignment is not just verticle or "up/down" like we see things, it also has a "left/right" element. My tranny was sitting way off center. Getting the tranny centered in the tunnel made a big difference in reducing the vibration.

[1970Moparmann]

This may not be applicable but: I had a problem once where I had a lot of vibration at lower to medium speeds but when at highway speeds, it smoothed out.  The problem turned out to be the U-Joints.  Some Rollers had fallen out of the bearings.

Funny how I was just talking to a friend when I saw this thread.  My Coronet is doing the same thing.  A buddy said that it is probably an improper seated U Joint.  Anyways, I'm taking the drive shaft out tonight, getting a new U joint and having the shaft balanced to be safe.

I'll report back........

[Big Sugar]

Well mike check that the tranny is centred while your under there .....Paul G may have something there.    I guess you would need to back to the engine mounts and loosen them off to get the tranny sitting centre in the tunnel.


Ron

[ottawamerc]

How can you tell if it is centered properly ? Just a visual thing?
Scott

[MaximRecoil]

Ok if someone finds the solution to this it HAS to become a sticky On my drive home last nite from Moparfest getting the soothing vibration from my car I got to thinking, is it possible that we are just used to our new rides being smoother and 40+ yrs ago this type of vibration was the norm?

Scott

I don't think so. My '69 is a former "General Lee":



And it has been jumped through the air, suffering a pretty hard nose-forward landing at some point in the distant past. Some previous owner more or less straightened it out, but the crumples and waves in the steel (e.g., inner fenders, subframe rails) where the nose had bent upward can still be seen, the underside of the K-frame is still dented in, the front valance is still mangled on one side, the radiator chair is bowed, the driver's side fender was mangled and then straightened/Bondo'd, the frontend bushings and front shocks were utterly trashed (I replaced all the bushings, sway bar links, etc. in the frontend, along with the shocks, then got a frontend alignment at my local Chrysler dealership), and so on.

This is what it looked like just before I hauled it out of the Maine woods in 2011, where it had rested since 1994:



In any event, that car (318 automatic, 2.71:1 gear ratio in the rearend) goes down the highway at e.g. 75 slick as hell; not a hint of vibration, and it tracks straight too. I don't think the transmission, driveshaft, or rearend has ever been messed with by any of the previous owners. The only thing I've done in those areas is replace a missing rearmost U-joint (the driveshaft had been disconnected for towing at some point, and the U-joint was long gone), and replace the axle grease seals in the rearend, because one of them was leaking grease onto my brakes.

So if my car, which has had a very rough life to say the least, can go down the highway without vibrations, they could no doubt do it when new, and yours can no doubt do it too, if the problem can be pinpointed.

[Cooter]

Ok if someone finds the solution to this it HAS to become a sticky On my drive home last nite from Moparfest getting the soothing vibration from my car I got to thinking, is it possible that we are just used to our new rides being smoother and 40+ yrs ago this type of vibration was the norm?

Scott

Winner, Winner, Chicken dinner. Interstate speeds were ALOT slower, and back then I can't remember anybody ever telling me that they "Didn't realize they were going 80 MPH it was so smooth" as they tend to do today. You KNEW when you were going that fast back then because you were wrestling an alligator at those speeds to keep it straight. Once you begin to swap around all these OD trannies, everything must be re-engineered in order to be back where the driveshaft speeds can handle being in OD with like 3.55-4.10 gears.

[1970Moparmann]

Well mike check that the tranny is centred while your under there .....Paul G may have something there.    I guess you would need to back to the engine mounts and loosen them off to get the tranny sitting centre in the tunnel.


Ron

Ron, I did a few years ago and all looked good.   

[MaximRecoil]

Winner, Winner, Chicken dinner. Interstate speeds were ALOT slower, and back then I can't remember anybody ever telling me that they "Didn't realize they were going 80 MPH it was so smooth" as they tend to do today. You KNEW when you were going that fast back then because you were wrestling an alligator at those speeds to keep it straight. Once you begin to swap around all these OD trannies, everything must be re-engineered in order to be back where the driveshaft speeds can handle being in OD with like 3.55-4.10 gears.

Except, my car is smooth, not a hint of vibration, and tracks straight at 75 or 80 MPH, and it has been through hell. See above. The indicators of high speed in my car comes from wind noise and a somewhat loud exhaust. New cars are simply a lot quieter at those speeds; better aerodynamics, better sealing, more sound-deadening insulation, and quieter exhaust compared to my car. However, if you took a 1969 Cadillac, Lincoln, or Imperial down the highway, I'll bet it would be just as quiet as most new cars, and you could easily not realize you were doing 80.

As for interstate speeds being a lot slower back then: not necessarily true. For example, in my state:

The Maine Turnpike had a posted speed limit of 70 mph in the early 1970s, but as Maine then had no law against traveling less than 10 mph over the posted speed, the de facto speed limit was 79 mph.

The speed limit in Maine on I-95 and the Maine Turnpike is now 65 MPH, and you can get a ticket for exceeding it by any amount. As of 2 years ago, there is one section of I-95 in Maine (from Old Town to Houlton, about 100 miles) that has a 75 MPH speed limit, but that is still not as high as the de facto speed limit of the early '70s here.

[1970Moparmann]

Trans looks in line.  drive shaft angle looked good.  I dropped it off at the shop today and it will be ready tomorrow.  The main guy said "most likely" my heavy vibration is due to the drive shaft out of balance. 

I'll report back tomorrow.

[Cooter]

Obviously maximum, you must have the only perfect Charger that doesn't shake. As for the rest that open numerous threads about vibrations, these mostly weren't  'supposedly' "jumped"and vibrate all to hell.
2.76 gears do not spin the driveshaft as fast with 3spd auto as fast as a set of 3.55 or 4.10 gears in OD.
Therefore, you have less problems with vibrations that seem to creep up.
Btw:I'll have to take your word as to no shaking. (No proof or links)

[Paul G]

Maxim what are your pinion angles? Can you measure those? Bone stock angles, or at least angles from a car that has no bad vibs would be great info.

[flyinlow]

Paul,

Any road construction around you. Maybe tar or contaminate on driveshaft. When they shortened the shaft did they look inside it? good condition ,no  rust or mud?

Just a couple unusual thoughts on things that might cause the balance to change.  

Craig

[MaximRecoil]

Obviously maximum, you must have the only perfect Charger that doesn't shake. As for the rest that open numerous threads about vibrations, these mostly weren't  'supposedly' "jumped"and vibrate all to hell.

You didn't read my post so well. Let's see:

"maximum"?

"Perfect Charger" ... who claimed that? The imaginary "maximum" fellow?

"Only one that doesn't vibrate"? Who first determined that all other Chargers vibrate and then made such a ridiculous claim?

"Supposedly"? ... there is no "supposedly" about it; the car was jumped, or it sustained an impact with identical mechanics to a nose-forward landing from a jump of significant height. Either way, the end result is the same.

2.76 gears do not spin the driveshaft as fast with 3spd auto as fast as a set of 3.55 or 4.10 gears in OD.

First, they are 2.71 gears, not 2.76. Secondly, your claim is false with regard to the 3.55 gears in OD, and is only barely true for the 4.10 gears in OD. The A518 has a .69:1 gear ratio in OD, which effectively turns a 3.55 rearend gear into a 2.45. It effectively turns a 4.10 gear into a 2.83, which isn't much lower than my 2.71 gears.

Therefore, you have less problems with vibrations that seem to creep up.

See above.

Btw:I'll have to take your word as to no shaking. (No proof or links)

Do whatever you want. Given that I drive the car and you don't (nor have you ever), it follows that I know whether it vibrates or not, and you don't.

Maxim what are your pinion angles? Can you measure those? Bone stock angles, or at least angles from a car that has no bad vibs would be great info.

There's an angle finder at the garage. When I next get a chance I will.

[Cooter]

Again, you do not understand what your talking about regarding driveshaft speeds with OD trannies. I dismiss you out of hand. Please try again when you understand a little better. Maybe ask the guy that does all your work for you. And Maximum, as in maximum ass.

[ottawamerc]

Wow Cooter who pi$$ed in your cheerios this morning

Scott

[MaximRecoil]

Again, you fo not understand what your talking about regarding driveshaft speeds with OD trannies. I dismiss you out of hand. Please try again when you understand a little better.

Are you seriously trying to argue with basic math? In any event, you're flat out wrong. 3.55 × .69 = 2.4495. That's a fact. You obviously don't understand how to calculate a final drive gear ratio. A 3.55 rearend gear ratio is only effectively a 3.55 final drive gear ratio if the final drive gear in the transmission is 1:1 (such as with a 727, 904, A833, etc). Want to know why? Because 3.55 × 1 = 3.55, obviously.

Maybe ask the guy that does all your work for you.

There is no guy that does "all my work for me"; only a guy that does work involving fabrication. I do electrical and mechanical work myself.

And Maximum, as in maximum ass.

Dyslexia? Don't worry, it is nothing to be ashamed of.

[Cooter]

Ashamed? Once again, John was right. When you graduate from that briefcase you call a toolbox, then you might learn something other than what you think  you know.

[XH29N0G]

I'll jump in here with possible misunderstanding of the discussion. 

I have been running an OD gear for a the past 30 years, first with a 3.23 rear and now with a 4.30.  The OD makes it so the engine does not rev as high, by changing the ratio of the transmission.  This does not change spinning rates downstream of the transmission.  Since the driveshaft is between the transmission and the differential, it spins at a rate determined by the rear gears. 

When I switched to 4.30s, it was smooth until I stomped on it one time and believe a weight came off the driveshaft.  Then it vibrated like all get out.  I took it to a truck shop (big trucks, dump trucks, buses, semi's).  They balanced the driveshaft and the vibration went away.  I also believe that if I had a minor imbalance that I might not have seen it with the 3.23 gears, but would see it with the 4.30s.

More recently, I had another transmission installed with a new driveshaft and am tracking down a vibration at higher speed that changes depending on whether I am on or off throttle.  My first try is related to pinion angles, which I have now adjusted.  If that cures it, I will sign on again and let everyone know.  My understanding is that basically for pinion angles, the vibrations come about when the axis of the transmission and the axis of the differential are not parallel, and it is best not to have working angles that are too large (some say less than 3.5 degrees).

That is all I know.  As I understand it, other sources of vibration can be the rear of the transmission, a u joint, and tire balance.

[flyinlow]

Yea with OD trans and lower axle ratio's the driveshaft rotational speed gets up there. With 3.91 gears and 28" tires at 130mph I figured the driveshaft was spinning over 6000 rpm.

So with a .50 OD six speed with a .78 GV behind it and 5.13 gears do I need a carbon fiber driveshaft to go 200mph?   

[ws23rt]

I'll jump in here with possible misunderstanding of the discussion. 

I have been running an OD gear for a the past 30 years, first with a 3.23 rear and now with a 4.30.  The OD makes it so the engine does not rev as high, by changing the ratio of the transmission.  This does not change spinning rates downstream of the transmission.  Since the driveshaft is between the transmission and the differential, it spins at a rate determined by the rear gears. 

When I switched to 4.30s, it was smooth until I stomped on it one time and believe a weight came off the driveshaft.  Then it vibrated like all get out.  I took it to a truck shop (big trucks, dump trucks, buses, semi's).  They balanced the driveshaft and the vibration went away.  I also believe that if I had a minor imbalance that I might not have seen it with the 3.23 gears, but would see it with the 4.30s.

More recently, I had another transmission installed with a new driveshaft and am tracking down a vibration at higher speed that changes depending on whether I am on or off throttle.  My first try is related to pinion angles, which I have now adjusted.  If that cures it, I will sign on again and let everyone know.  My understanding is that basically for pinion angles, the vibrations come about when the axis of the transmission and the axis of the differential are not parallel, and it is best not to have working angles that are too large (some say less than 3.5 degrees).

That is all I know.  As I understand it, other sources of vibration can be the rear of the transmission, a u joint, and tire balance.

You are right about transmission final drive ratio vs the rear end ratio. Cooter was as well and said basically the same thing.

We are after all talking about drive shaft vibration and the final drive at the axial affects this not the engine rpm.
A 4-10 gear takes 4.1 turns of the drive shaft for one turn of the wheel. A 2-76 gear takes only 2.76 turns for one wheel rotation.

As for pinion angles. And just to be helpful.
1. Question? Why even have universal joints. -- The rear axial on leaf springs moves way to much in two directions for another type of coupling to be practical.

2. Question? Why the need for an initial offset (pinion angle).---The needle bearings in the joint need a minimum movement in order for them to roll completely. If they did not get that amount of movement they would just wiggle in place and take a set in the race. As well as not be able to circulate their grease. (premature bearing failure)

Another item not mentioned in the discussion about drive shaft vibration is "critical speed".

Any rotating member has a critical speed that when met will vibrate regardless of how well balanced it is.

Example of this is a long small dia. shaft for the purpose of a mental visual.
A shaft will sag from it's own weight.  As it starts to turn it will still have sag. As the speed increases the sag will creep toward the up side in the direction of rotation. The critical speed of this shaft will be the rpm at which the sag goes over the top. The shaft now looks like a jump rope.
This is a point that will cause much vibration.

There are other things that affect the "critical speed" rpm such as loose bearings , out of balance, induced vibration from another source (harmonics).etc.

A pulsing vibration could very well be a shaft moving in and out of critical speed.
A vibration that settles down as the speed increases could be that the shaft has passed first critical speed and is now moving towards the next critical speed. The next one is generally greater than the first. Eventually something will fail.

A limber shaft will have a lower critical speed than a stiffer one.
Also of course no vibration makes the bearings happy.

[Cooter]

Ever been under your newer truck? Wanna guess why that. 6"aluminim driveshaft is that big?


As mentioned,  and as was pointed out to me in another thread, gear ratios in the rearend stay the same whether you are cruising as they did back in the day with 4.10 gears and engine screaming at 4000rpm...
You didn't notice the vibration as much because you were concerned with the engine revs. Kinda like you expected a little shaking at those rpms...

Too many today seem to think that if their engine isn't turning the rpms, then the rest of the drivetrain isn't as well..

You are still turning 4.10gears, only difference is your tranny has made it a lot easier on your engine, but is killing your pinion bearings.

This is why most newer vehicles have synthetic oil in them. It's to try and keep bearings and the oil from breaking down from higher temps.

I see LOADS of Explorers in the shop with pinion bearings GONE due to an OD and 4.10 gears for like 150k miles.

[ws23rt]

Ever been under your newer truck? Wanna guess why that. 6"aluminim driveshaft is that big?


As mentioned,  and as was pointed out to me in another thread, gear ratios in the rearend stay the same whether you are cruising as tgey fid back in the day with 4.10 gears and engine screaming at 4000rpm...
You didn't notice the vibration as much because you were concerned with the engine revs. Kinda like you expected a little shaking at those rpms...

Too many today seem to think that if their engine isn't turning the rpms, then the rest of the drivetrain isn't as well..

You are still turning 4.10gears, only difference is your tranny has made it a lot easier on your engine, but is killing your pinion bearings.

This is why most newer vehicles have synthetic oil in them. It's to try and keep bearings and the oil from breaking down from higher temps.

I see LOADS of Explorers in the shop with pinion bearings GONE due to an OD and 4.10 gears for like 150k miles.

Absolutely correct   Maxim was so quick to dismiss something he failed to read what was said and understand it. A clue to what the topic is is at the very top of the thread. It however is not colored or in "bolding"? a made up word but we know what he was talking about anyway.

[cdr]

if my car ever goes down the road,with my 4.57 & .69 overdrive,engine at 6000 rpm,my drive shaft rpm will be right at 8700 rpm. i will need an alum 3.5 shaft.

[MaximRecoil]

I'll jump in here with possible misunderstanding of the discussion.  

I have been running an OD gear for a the past 30 years, first with a 3.23 rear and now with a 4.30.  The OD makes it so the engine does not rev as high, by changing the ratio of the transmission.  This does not change spinning rates downstream of the transmission.  Since the driveshaft is between the transmission and the differential, it spins at a rate determined by the rear gears.  

This is all correct. I was only considering how the effective final drive ratio affects engine RPM, which was an error on my part, given the context of this thread.

So for example, a car with a 3.55 rearend at ~65 MPH in .69:1 OD will have an engine RPM of ~2000 and a driveshaft RPM of ~2900.

My car's engine and driveshaft, with its 2.71 rearend and 1:1 top transmission gear, would both be at ~2200 RPM when going ~65 MPH.

By the way, both of those examples assume an average size tire, something like a 215/70R15. My engine and driveshaft's actual RPM at 65 MPH is a little lower than that, about 2100, because my tires are 235/70R15.

[Cooter]

What are most driveshaft shops balancing driveshafts to??
I know back in the day it was only around 3000rpms.

[ws23rt]

I'll jump in here with possible misunderstanding of the discussion.  

I have been running an OD gear for a the past 30 years, first with a 3.23 rear and now with a 4.30.  The OD makes it so the engine does not rev as high, by changing the ratio of the transmission.  This does not change spinning rates downstream of the transmission.  Since the driveshaft is between the transmission and the differential, it spins at a rate determined by the rear gears.  

This is all correct. I was only considering how the effective final drive ratio affects engine RPM, which was an error on my part, given the context of this thread.

So for example, a car with a 3.55 rearend at ~65 MPH in .69:1 OD will have an engine RPM of ~2000 and a driveshaft RPM of ~2900.

My car's engine and driveshaft, with its 2.71 rearend and 1:1 top transmission gear, would both be at ~2200 RPM when going ~65 MPH.

So is this an admission that you misread/misunderstood a post and proceeded to explain something that was off topic?

OOps I see that you changed your post to that effect.    

[Paul G]

What are most driveshaft shops balancing driveshafts to??
I know back in the day it was only around 3000rpms.

Denny's website states they can balance up to 10,000 rpm. It does not say they do balance every shaft to 10,000 rpm though. The last shop that balanced mine had it on a jig that was spinning at a very low speed. I would guess no more than 1500 rpm imo. So I doubt my DS has ever been high speed balanced. 

quote from Denny's;
Is driveshaft balance really necessary?

YES!  Driveshaft balance is necessary for smooth driveline operation and to eliminate the destructive effects that an unbalanced or poorly balanced driveshaft will have on your transmission and rear end.   At Denny's Driveshafts we High Speed High RPM Balance every driveshaft to meet or exceed the top rpm requirements of your engine and transmission, especially in the case of an overdrive transmission where the driveshaft rpm is greater than the engine rpm in high gear.   This is very important and should not be overlooked when purchasing a new driveshaft.  We can balance and test to 10,000 rpm so whatever your requirements are we can meet them.   This will ensure that you will have the smoothest ride at all road speeds and track speeds and also a quicker ET.  You won't be limited by rear end gear ratio and you will experience smooth running especially when using an overdrive transmission.    True high speed balance means balancing at a High RPM. 

[ws23rt]

What are most driveshaft shops balancing driveshafts to??
I know back in the day it was only around 3000rpms.

Denny's website states they can balance up to 10,000 rpm. It does not say they do balance every shaft to 10,000 rpm though. The last shop that balanced mine had it on a jig that was spinning at a very low speed. I would guess no more than 1500 rpm imo. So I doubt my DS has ever been high speed balanced. 

quote from Denny's;
Is driveshaft balance really necessary?

YES!  Driveshaft balance is necessary for smooth driveline operation and to eliminate the destructive effects that an unbalanced or poorly balanced driveshaft will have on your transmission and rear end.   At Denny's Driveshafts we High Speed High RPM Balance every driveshaft to meet or exceed the top rpm requirements of your engine and transmission, especially in the case of an overdrive transmission where the driveshaft rpm is greater than the engine rpm in high gear.   This is very important and should not be overlooked when purchasing a new driveshaft.  We can balance and test to 10,000 rpm so whatever your requirements are we can meet them.   This will ensure that you will have the smoothest ride at all road speeds and track speeds and also a quicker ET.  You won't be limited by rear end gear ratio and you will experience smooth running especially when using an overdrive transmission.    True high speed balance means balancing at a High RPM. 

This sounds great if that is indeed what they do.

[Paul G]

Paul,

Any road construction around you. Maybe tar or contaminate on driveshaft. When they shortened the shaft did they look inside it? good condition ,no  rust or mud?

Just a couple unusual thoughts on things that might cause the balance to change.  

Craig

That shaft is clean, painted and polished..... on the outside. Never saw the inside. Last spring when I broke the trans was the last time the DS was off the car, and in the machine shop for a balance and new u joints. I am probably going to pull the DS this weekend or next and get some measurements for a new DS. It sounds like the thing to do next, maybe?

Denny's says stock drive shafts are not intended for race applications.

Quote from Denny's
Why did my driveshaft tubing twist or break?

There are many reasons. If you are using a stock driveshaft in a racing application then you already know the answer. Stock shafts should never be used for racing. If you had a driveshaft built by a driveline shop and it has broken or twisted the tubing then you should take it back to where you bought it. They apparently built your driveshaft with tubing that was similar to stock driveline tubing or possibly selected a tube diameter or thickness that was not correct for your application. Just because the shop builds dump truck shafts does not mean it can handle the requirements of a race car.
[end quote]

My Charger is not a race car by any means. But it does do a lot of this. And with the recent carb swap and tweeking it can do a decent second gear burn out. That only puts more load on the shaft at higher rpm when it tends to wobble around any way. I don't know?

[ws23rt]

Paul,

Any road construction around you. Maybe tar or contaminate on driveshaft. When they shortened the shaft did they look inside it? good condition ,no  rust or mud?

Just a couple unusual thoughts on things that might cause the balance to change.  

Craig

That shaft is clean, painted and polished..... on the outside. Never saw the inside. Last spring when I broke the trans was the last time the DS was off the car, and in the machine shop for a balance and new u joints. I am probably going to pull the DS this weekend or next and get some measurements for a new DS. It sounds like the thing to do next, maybe?

Denny's says stock drive shafts are not intended for race applications.

Quote from Denny's
Why did my driveshaft tubing twist or break?

There are many reasons. If you are using a stock driveshaft in a racing application then you already know the answer. Stock shafts should never be used for racing. If you had a driveshaft built by a driveline shop and it has broken or twisted the tubing then you should take it back to where you bought it. They apparently built your driveshaft with tubing that was similar to stock driveline tubing or possibly selected a tube diameter or thickness that was not correct for your application. Just because the shop builds dump truck shafts does not mean it can handle the requirements of a race car.
[end quote]

My Charger is not a race car by any means. But it does do a lot of this. And with the recent carb swap and tweeking it can do a decent second gear burn out. That only puts more load on the shaft at higher rpm when it tends to wobble around any way. I don't know?

You could be the quality control tester for their drive shafts.   They should pay you for the service.

[Cooter]

I would think as long as you ain't trying this, you'll be ok with one of theirs.

I wonder who does Sean's [Farmtruck] Drive shafts?

[ws23rt]

I would think as long as you ain't trying this, you'll be ok with one of theirs.

I wonder who does Sean's [Farmtruck] Drive shafts?

[chargerbr549]

Here is a good read on a driveline vibration problem that he finally solved. He ended up balancing the shaft on the car.
http://www.dodgecharger.com/forum/index.php/topic,63413.0.html

I had a driveline vibration problem on a dodge dakota that I had, at lower speeds it was fine but when it got up to speeds above 30mph it would start to vibrate so I took it to a driveline shop to get it balanced and it didn't really change the vibration much so I figured out the rpm that the driveshaft was spinning when it started to vibrate and it was around 3000 rpm so I talked to the shop that balanced the shaft the first time and their machine didn't spin it anywhere near 3000 rpms and told me that it should be fine at the lower rpms that they balanced it to, it wasn't, so I finally found a shop that could balance it well above 3000 rpms and presto the problem was solved!!!

[ottawamerc]

Ok so here's what I found today with mine. Last time I checked my pinion angle it seemed like it was off by 2 1/2- 3* so I ordered some 2* shims. I received them today and all excited to finally cure this vibration I installed them. Now while the car was still on the jacks I tried running it without the wheels on. Well the vibration was worse I cranked up the idle screw to keep it at 40MPH then had a peek under the car, the diff was smooth but the transmission tail shaft was visibly shaking,,, AH HA ! there it is!! OK so I am assuming that A: it is from the front of the shaft causing the shake? and B: that it has to be the front yoke because I used the same yoke on both of the drive shafts I tried and balanced, also the U Joint which is a brand new $40 Spicer unit can have the caps installed and removed without pressing them??? (never had that before)

So do you guys think this could be it? I will try another front yoke and use the good but used u joint that is installed in it. I'll update with any findings.

P.S. sorry about the long post.

Scott

[Cooter]

How far up in the tail shaft is the driveshaft now? I've seen where the driveshaft wasn't quite long enough and not fully seated up in the housing.
How's the rear tail shaft bushing?

[ottawamerc]

It's in so there is about an 1 1/2" left and the tail shaft bushing and seal has been replaced recently.

Scott

[firefighter3931]

It's in so there is about an 1 1/2" left and the tail shaft bushing and seal has been replaced recently.

Scott

Scott, mine has the same amount of yoke showing at static ride height with no vibration issues whatsoever.

The front yoke is the problem....if the u-joint caps are as loose as you've described then the yoke has excessive wear. Front yokes do go bad and often on visual inspection they appear to look fine....but they're not. I'm pretty sure the surface the rides on the output bushing has some wear on it as well and is probably undersized.


Ron

[1970Moparmann]

Based on what I posted earlier, I thought I would give an update.  I had my driveshaft balanced, it was way off.  My U's were also bad.   I put the driveshaft back in the car, and now, which was a really bad vibration, is now very small at the same speeds.  I have to check my angles now....

[Paul G]

Last week I called Denny's Driveshaft and placed my order for a new heavy duty DS. Daniel from Denny's called me today and said that Denny looked over my order form and there is a problem. The slip yoke from a 727 will fit on the output shaft of an A518, except, the A518 output shaft is a hair smaller even though it is a 30 spline shaft, if they use a slip yoke for a 727 to build the new shaft it will have some vibration, mainly when on and off the gas, and I do have this issue at highway cruising speeds. This is the first I have heard of this. Can anyone verify this?

Denny said he could make the new shaft with a 727 slip yoke, but could not get a new slip yoke for an A518, none are being reproduced. I just called my local dealer and he can get a slip yoke for 1995 Ram 1500 with a 360. Part #52097819. I asked him if this slip yoke is the same for an older vehicle with a 727? He could not verify that. But said he would think the u-joints from an A518 truck shaft would be bigger than the u-joints from a car with a 727.

So I don't know why Denny could not get one? Maybe it is an issue with the supplier he uses? U-joint issue?   

[flyinlow]

 


Please don't tell  my Charger. The 727 yolk has been working for over 20 K. miles.

[Cooter]

I thinkn I read somewhere  the 518 uses metric/odd  sized output shaft or something now that you mention it...

[Paul G]

I took a look at PATC website and they list a yoke specifically for the 90 to 95 A518.

[Paul G]

Called PATC and have an A518 slip yoke coming to me. I hope and pray that ends my vibration issues.

[Paul G]

Got the new slip yoke this week. Now if I can find the time to get my big azz under the car today??

[Sublime/Sixpack]

Sometimes it's just plain necessary to "Field Balance" a driveshaft!   (In other words, balance the driveshaft in the car).
Mopar Performance's "Chassis" manual describes this quite well in Chapter Six.

The manual I have is Part # P5249441

[Paul G]

Got the drive shaft back in the car and went for a ride. The correct slip yoke from PATC made a very noticeable difference. The RRRrrrRRRrrrRRRrrr sound is now almost gone completely. It was well worth the effort. Apparently Denny was right. I had some trouble getting the U-joint back in. Couldn't get the caps back in far enough to clip them in. Ended up smashing the little needle that fell out of place, and I mean smashed. It is unbelievable what you can do with a big enough hammer!   That U-joint didn't feel right any way. It moved easily in it's normal field of travel, but got stiff beyond that. It only had a few thousand miles on it. I used a new Precision 316 U-joint from Napa. They said it was a big block U-joint. I hope it will hold up.

Now I need to have the wheels balanced again. I have some vibration that seems to travel from front to rear and back again. I can feel it in the floor and seat mostly. Lets see if wheel balance may cure that.

I am going to have this Charger driving as smooth as a big Chrysler one day!  

[flyinlow]

Glad you where able to fix the problem.

Pease elaborate.

The two A518's I have waiting for projects I pulled from vans at a junkyard and have the yolks with them. The width  of the yolks u joint is bigger  that the 727 yolk (7290) , but they where truck driveshafts. The outside diameter of the part that slides over the tailshaft  and into the trans appears to be the same as  the 727 yolk.

What is different?

[Paul G]

The difference is, the output shaft of the A518 is slightly smaller than the output shaft of a 727, according to Denny at Denny's Driveshaft. I never knew this till now. Some say the A518 output shaft was built to a metric dimension, I am not sure about that, did not verify it? The 727 yoke will fit in to the A518 tranny and seem like it will work, I could not feel a difference between the two yokes when sliding them in my A518. Probably because the outside diameter of the two yokes are the same. I don't know that for sure either. Since you have an original A518 yoke, if you could, try to slide it in to a 727 and see if it will go. I have read in other places, people say an A518 yoke will bind in a 727, and wont go in all the way. I do know that a lot of the vibration went away with the new yoke from PATC, which they say is for a 90 to 95 A518.

As far as the U-joint. A518's were only used in trucks, which probably gets the big U-joint, I don't know? Is the 727 yoke you have from a big block or small block 727 tranny? According to Napa the big block cars get a bigger U-joint than small block cars. ?? My old 727 yoke and the drive shaft used the big U-joint, same U-joint the new yoke from PATC required.   

BTW, I had the wheel balance checked. They added 1/4 oz of weight to one front wheel. So the little vibs I have left are not in the wheel balance. Got to keep looking. Still suspect that POS drive shaft.   

[flyinlow]

Thanks, Paul,

727 yolk is from a BB.  I will try the 518 yolk  in a 727 trans . 

[Big Sugar]

Any updates ?

I found a low mile dakota ALUMINUM driveshaft from a A518 setup, im wondering if I should just setup my conversion plan with that driveshaft as opposed  to the 727 driveshaft i have now.



Ron

[ws23rt]

Any updates ?

I found a low mile dakota ALUMINUM driveshaft from a A518 setup, im wondering if I should just setup my conversion plan with that driveshaft as opposed  to the 727 driveshaft i have now.



Ron

I've been looking for updates myself.   The dakota alum. drive shaft you have most likely will have to be altered to the length you need. But it sounds like a good way to go.
BTW are the yokes aluminum also?--I'm not up to speed on the alum. shafts

[flyinlow]

Paul and others,

Sorry for the delay. 

I tried the A518 yolk in my old 727. Dose not fit. Goes in until the splines touch. I have a 2004 Ram 2X4 yolk for a 545rfe. It dose the same thing. Fits the A518 ,but not the 727.

Damn. I have been running around for five years with an improper fitting yolk. (727 yolk)  I guess I have an other Winter project. Hope I have not messed up the 518 tail shaft splines in the car.

Paul ,what u joint did you use? My 518 yolks are 3.66" outside dimension. Bigger than a 7290. I will have to find a conversion joint, or have the driveshaft redone.

Craig

[Paul G]

Precision 316 U-joint from Napa. So Denny was correct. I know it made a big difference for me using the correct A518 slip yoke.

[Big Sugar]

Well thats good to hear ! At least we're getting to the bottom of it,



Ron