Aluminum driveshaft installed and now have a new problem.

[RECHRGD]

Some of you know that I have been battling a driveline vibration for years since installing a Gear Venders OD.  I narrowed it down to having to balance the driveshaft while on the car to get the smoothest operation possible.  I got it to where it was livable, but still had a little vib between 60 &70mph.  This year I decided to bite the bullet and get an aluminum driveshaft and that with less rotating mass, life would once again be good.  Took the car out for it's first drive of the season today with high expectations.  When first pulling out into the roadway I felt a little wobble from the rear but just figured it was something in the road.  I drove at highway speeds and it seemed that the vibration was now gone except for maybe a little around 75 or so.  I accelerated to over 100 at part throttle and all seemed pretty smooth.  So at this point I'm pretty happy and decide to get a little more frisky with the car.  I accelerated from 50 to 70, fairy hard but not full throttle, and felt more driveline vibration.  Not happy!  Came to a stop light and when leaving felt the wobble again.  Not happy!  I then pulled into a weigh station area that was empty to try a hard launch, but not enough to spin the tires.  I gave it about 3/4 throttle from a stop and I thought the rear end had come loose.  Really not happy!  It felt like I would imagine a car with bad wheel hop would feel like.  So nothing is different from when I put the car away last fall except for the lighter driveshaft.  The one thing I never liked, was the pinion angle I ended up with after the GV install.  I was unable to get a nose down angle on the pig and had to settle for a nose up angle.  It's been that way for years with no problem and plenty of full throttle blasts.  Could the lighter DS now have caused the pig up angle to be a problem?  Any ideas?  Unhappy Bob......

[firefighter3931]

Bob, i'm willing to bet that pinion angle is your problem. 

The fact that vibration increases under hard acceleration leads me to this conclusion. When a car is launched hard the pinion will rotate up towards the floorpan...the harder it launches, the more it rotates. 

You really should have 2* nose down of pinion angle with a factory style XHD spring....more if you're running a Super stock leaf pack.


Ron

[RECHRGD]

Thanks Ron.  It just seems strange that just a little less weight on the DS would now make a problem out of what was't a problem for years.  The problem with the gear vendors, is that it mounts at the end of the tail piece off the tranny and prevents the tinny from being adjusted up at all.  Maybe some GV owners can chime in and I can see what they've done.  In the meantime I'll go back and trailer the car home so I can use the lift in the shop to try and figure this thing out.  It's a real pain living off a gravel country road when you're into cars.....

[cdr]

also,if you have ubolts on the rear ujoint it is easy to get them to tight & it will make the joint bind up,you should use locktite & get them snug,if you have straps disregard.

[RECHRGD]

I do have the u-bolts.  Do you know what they should be torqued at?

[BSB67]

I do have the u-bolts.  Do you know what they should be torqued at?

Did you always have u bolts?  What kind?

[RECHRGD]

I do have the u-bolts.  Do you know what they should be torqued at?

Did you always have u bolts?  What kind?

Yes, I've had them from probably '99, but have never known how tight they should be.  I got them from Year One.  I know that when I was taking off the steel DS I found a couple of the nuts to be loose on the u-bolt, so I'm sure I tightened them more than before when installing the aluminum DS......

[cdr]

i tighten them just enough to flatten the lock washer & lots of blue locktite on threads.

[cdr]

i just put my alum drive shaft in,i think i am going to go with lock nuts.

[firefighter3931]

i tighten them just enough to flatten the lock washer & lots of blue locktite on threads.

Same here...but i use Nylock nuts. Tighten until the lock washer goes flat and call it good. Haven't had any loosen off yet. 

Ron

[RECHRGD]

Got the car back home and up on the lift.  The u-bolts were not really all that tight on the u-joint and it looks and feels fine.  The nice new aluminum yoke on the DS took a beating though on my launch gone bad.  It should be OK, just need to file off some rough edges.  So, it's got to be the pinion angle.  To get to a 2* down angle on the pig, as Ron suggests, I will need to get to a 2* up angle on the tranny tailpiece.  Doing that will raise the Gear Vendors unit up at least an 1 1/2".  To make that happen I will have to take off the GV unit and beat the heck out of the tunnel area of the floor to make the room.  Maybe I'll start another thread to pull in some of the guys that are running the GV's to see what they've done.

[cdr]

you need to put shims in the rear end.

http://chucker54.stores.yahoo.net/noname45.html

[cdr]

[RECHRGD]

Thanks,  I've got plenty of shims from fighting this battle previously.  The problem comes in when trying to keep the tailpiece and pig on parallel but opposite angles, as recommended.....

[cdr]

 put an adjustable pinion snubber or some caltracs to get rid of the spring wrap up you are having.

[Sublime/Sixpack]

The correct wedges under the rear spring perches should give you the 2 degrees down of the pinion in relation to the trans. output shaft. That's what you're after right?

[ottawamerc]

Ok so after a bunch of research and trial and error on this that I did last year this is what I came out with: the pinion angle needs to be equal and opposite to the tranny output right! so lets say your GV output is at 0*+1* up then your pinion needs to be 0*-2* down. (more down because of spring deflection). So if your GV fits where it is now find out what your degree is + or - then shim your pinion. I could be 100% wrong (typically are)    Also remember that the longitudinal angle must be equal, thats whats was eventually wrong with mine. A simple string pulled tight thru the motor/ transmission and pinion center line will confirm this  

Scott  

[RECHRGD]

The correct wedges under the rear spring perches should give you the 2 degrees down of the pinion in relation to the trans. output shaft. That's what you're after right?

Correct, but when the current output shaft is at 5* down from front to back the amount of change at the pig is beyond reasonable.  I'm no expert, but I'm basing my thoughts on what I've gathered on threads here and on google....,

[Bobs69]

Has the drive shaft been high speed balanced?  Gear vendors says you must do this.  If not, too bad.  Dodges don't have much of an angle up and down for the drive shaft according to them, that's why the engine is set back on one side more then the other (to make up for this).

[RECHRGD]

Has the drive shaft been high speed balanced?  Gear vendors says you must do this.  If not, too bad.  Dodges don't have much of an angle up and down for the drive shaft according to them, that's why the engine is set back on one side more then the other (to make up for this).

The driveshaft balance does not come into play with the issue I'm having.  But Wow! Now you throwing in a side to side angle into the equation.  I'm going to go pour a scotch.........

[b5blue]

Just a shot in the dark here but the lighter DS would reduce the at speed vibration but possibly offer less dead weight against axle windup?  Could lowering height of the shackles or raising the front eye bolt holes somehow correct pinion angle just enough to stop bind up?     

[RECHRGD]

Just a shot in the dark here but the lighter DS would reduce the at speed vibration but possibly offer less dead weight against axle windup?  Could lowering height of the shackles or raising the front eye bolt holes somehow correct pinion angle just enough to stop bind up?     

Maybe, I'll be looking at any and all solutions.  This was going to be my final fix after years of living with a less than perfect set-up.  I feel like just taking off the GV and using it for target practice.....

[firefighter3931]

The correct wedges under the rear spring perches should give you the 2 degrees down of the pinion in relation to the trans. output shaft. That's what you're after right?

Correct, but when the current output shaft is at 5* down from front to back the amount of change at the pig is beyond reasonable.  I'm no expert, but I'm basing my thoughts on what I've gathered on threads here and on google....,

Bob, if the output on the trans/GV is 5* down then you need to get the pinion at 7* nose down to achieve the desired 2* nose down result. 

Shim stacking may be difficult depending on where it is now ? 

There are two options the way i see it :

(1) Have custom shims/blocks made to correct the pinion angle. You will need longer u-bolts to make this work

(2) Cut the spring perches off the axle tubes and have them rewelded with the proper pinion angle adjusted into the axle housing

I'd be interested to see where your current pinion angle is at on the differential. 

If as you stated previously the pinion is pointed up...we know that the pinion angle is waaaay off and needs correction. 



Ron

[RECHRGD]

The correct wedges under the rear spring perches should give you the 2 degrees down of the pinion in relation to the trans. output shaft. That's what you're after right?

Correct, but when the current output shaft is at 5* down from front to back the amount of change at the pig is beyond reasonable.  I'm no expert, but I'm basing my thoughts on what I've gathered on threads here and on google....,

Bob, if the output on the trans/GV is 5* down then you need to get the pinion at 7* nose down to achieve the desired 2* nose down result. 

Shim stacking may be difficult depending on where it is now ? 

There are two options the way i see it :

(1) Have custom shims/blocks made to correct the pinion angle. You will need longer u-bolts to make this work

(2) Cut the spring perches off the axle tubes and have them rewelded with the proper pinion angle adjusted into the axle housing

I'd be interested to see where your current pinion angle is at on the differential. 

If as you stated previously the pinion is pointed up...we know that the pinion angle is waaaay off and needs correction. 



Ron

Thanks Ron.  I'm having second thoughts on my measurement on the tailpiece.  I got the 5* down from the oil pan rail.  But I was just out in the shop and took a vertical measurement at the end of the tailpiece and it read 90*.  If that's the case, then things are much more workable.....

[b5blue]

Just a shot in the dark here but the lighter DS would reduce the at speed vibration but possibly offer less dead weight against axle windup?  Could lowering height of the shackles or raising the front eye bolt holes somehow correct pinion angle just enough to stop bind up?     

Maybe, I'll be looking at any and all solutions.  This was going to be my final fix after years of living with a less than perfect set-up.  I feel like just taking off the GV and using it for target practice.....

I've followed your subject a long time and you have me never wanting to add G.V. at time. 

[Sublime/Sixpack]

The correct wedges under the rear spring perches should give you the 2 degrees down of the pinion in relation to the trans. output shaft. That's what you're after right?

Correct, but when the current output shaft is at 5* down from front to back the amount of change at the pig is beyond reasonable.  I'm no expert, but I'm basing my thoughts on what I've gathered on threads here and on google....,

Bob, if the output on the trans/GV is 5* down then you need to get the pinion at 7* nose down to achieve the desired 2* nose down result. 

Shim stacking may be difficult depending on where it is now ? 

There are two options the way i see it :

(1) Have custom shims/blocks made to correct the pinion angle. You will need longer u-bolts to make this work

(2) Cut the spring perches off the axle tubes and have them rewelded with the proper pinion angle adjusted into the axle housing

I'd be interested to see where your current pinion angle is at on the differential. 

If as you stated previously the pinion is pointed up...we know that the pinion angle is waaaay off and needs correction. 



Ron

[RECHRGD]

Just a shot in the dark here but the lighter DS would reduce the at speed vibration but possibly offer less dead weight against axle windup?   Could lowering height of the shackles or raising the front eye bolt holes somehow correct pinion angle just enough to stop bind up?    

Maybe, I'll be looking at any and all solutions.  This was going to be my final fix after years of living with a less than perfect set-up.  I feel like just taking off the GV and using it for target practice.....

I've followed your subject a long time and you have me never wanting to add G.V. at time.  

The funny thing is, most people have no problems at all.  I'm just lucky, I guess.....

[Sublime/Sixpack]

Bob, if the output on the trans/GV is 5* down then you need to get the pinion at 7* nose down to achieve the desired 2* nose down result. 

.
Ron
[/quote]


[/quote] I may have "yes nodded" too soon. Ron, this doesn't sound right to me.

[b5blue]

Bob we have the same luck!  (none)

[firefighter3931]

Ok, scratch my previous message....must have been having a brain fart.   I was thinking of mine which had the opposite problem that Bob is having....my trans output points up...not down  

Bob, here's a chart that you may or may not have seen.

Pull the driveshaft and using an angle finder place it on the trans seal and yoke flange as illustrated in the top of the pic. This will give us the differentials between the two. The idea is to get the centerline paralell.

If the trans seal is indeed 5* down then the pinion needs to be 5* up to achieve a 0* pinion angle. Then you have to subtract 2* to correct for axle windup under hard acceleration.

I'll be interested to see what numbers you come up with  


Ron


Here's the link : http://www.moparts.org/Tech/Archive/axle/8.html

[b5blue]

You linked to reply same topic Ron.

[cdr]

Ok, scratch my previous message....must have been having a brain fart.  I was thinking of mine which had the opposite problem that Bob is having....my trans output points up...not down 

Bob, here's a chart that you may or may not have seen.

Pull the driveshaft and using an angle finder place it on the trans seal and yoke flange as illustrated in the top of the pic. This will give us the differentials between the two. The idea is to get the centerline paralell.

If the trans seal is indeed 5* down then the pinion needs to be 5* up to achieve a 0* pinion angle. Then you have to subtract 2* to correct for axle windup under hard acceleration.

I'll be interested to see what numbers you come up with 


Ron


Here's the link : http://www.dodgecharger.com/forum/index.php?action=post;topic=109927.25;num_replies=28

all this that has been said depends on the trans yoke being higher up than the yoke on the rear end.

to make it real easy check that 1st & let us know.

[firefighter3931]

You linked to reply same topic Ron.

Geez, some days it just doesn't pay to get out of bed  Maybe i should just stop posting on Bob's thread, lol 

Thanks for the heads up Neal....fixed it ; proper link now in place. 


Ron

[RECHRGD]

OK, being that we know that the pinion needs to go down regardless of the other angles I went ahead and turned around the 4* shims that were giving it a 6.5* nose up angle.  That produced a 5* nose down angle.

Here is what I started with:  from front to rear the tailpiece of the tranny dropped 5*.  The DS angled up 2* to meet the pig.  From rear to front the pig angled up 6.5* to meet the DS.  This setup got me pretty close to the parallel but opposite recommended scenario, but with every thing going in the opposite direction that I need.

After turning the shim around this is what I am left with:  From front to rear the tailpiece still has the 5* drop.  The DS now angles down 1* to the pig.  From rear to front the pig now angles 5* down.

I can get about 1* of drop out of the tailpiece if need be, but no more.  I guess the next question is; just how critical is the parallel but opposite configuration?  I could use some 2.5* shims I have and that would put the pig at 3.5* down and probably get the DS on a slight upward angle.  The saga continues......

[cdr]

I WOULD want the 3.5 down.then go drive it

[RECHRGD]

I WOULD want the 3.5 down.then go drive it

That's what I was thinking too.  Looks like rain for the next few days so the drive will have to wait.

[Bobs69]

gear vendors has a good tech line.......

[fy469rtse]

Can I throw in something else into the equation, I remember one other member having vibration issues regardless of pinion angles and such ,
After all it turned out to be the slip yoke, something about 518 and 727 splines not quite the same, maybe? relying on memory , but vendors assume they are, have a look for thread , slight differances in out put shaft od 
Each would fit the 727 spline but not the other way round just a thought

[RECHRGD]

Can I throw in something else into the equation, I remember one other member having vibration issues regardless of pinion angles and such ,
After all it turned out to be the slip yoke, something about 518 and 727 splines not quite the same, maybe? relying on memory , but vendors assume they are, have a look for thread , slight differances in out put shaft od 
Each would fit the 727 spline but not the other way round just a thought

That was probably my old thread.  The different yoke didn't work.  Finally got into the livable range by spending hours and hours balancing the driveshaft while on the car.  Should have left well enough alone.....

[fy469rtse]

Can I ask a silly obvious question , you have tried other wheels too, a friends car had a vibration, tracked it down to perfectly balanced wheels just not straight, picked up on this only because I was following him ,

[RECHRGD]

Can I ask a silly obvious question , you have tried other wheels too, a friends car had a vibration, tracked it down to perfectly balanced wheels just not straight, picked up on this only because I was following him ,

Back when I was fighting the initial vibration problem, I even took the wheels off and ran the car up to speed with the rear jacked up.  The vib was still there.....

[Bobs69]

Has the drive shaft been high speed balanced?

[RECHRGD]

As I said before, at this moment, anyway, I'm not chasing a vibration.  I'm simply changing pinion angles so I can accelerate without the pig rotating out of its normal range and tearing things up.  When dealing with the original small driveline vibs after the GV install, I had two different driveshafts built and both were high speed balanced.  The only way I ever got the vibs down to a livable level was by rebalancing the DS on the car.  Spent many hours trying different weights at different spots.  The aluminum DS was just my last effort to kill off the last of the vibs by having less rotating mass.  Go read the original post.......

[Bobs69]

I read it.  Read it again like you said.  I'll watch to see how you solve this.  Guess I was one of the lucky ones.