Advice needed in tracking down source of driveline vibrations

[XH29N0G]

As many probably know, I have been tracking down the source of drivleline vibrations.   I am trying to decide on a plan of attack to get rid of them and would appreciate any help or advice I can get

Driveline angles:  I had thought it was related to driveline angles (and some of it may have been), but now I have the transmission and the carrier parallel to within 0.5 degrees of each other.  The front angle is 3 degrees and the rear is 3 degrees in the opposite sense.  The angles were not correct at the start and the situation has improved.

Presently, the vibrations start around 60m mph and get progressively worse at higher speeds.  I have 27 inch tires and 4.30 rear so the propeller shaft is spinning fast.

My thoughts are as follows:

I wonder whether it is worth having the driveshaft balanced.  It was a new driveshaft with the install from Hurst drivelines.  (I ask because I have had an issue with another driveshaft that was cured with a balance.  The vibrations there came on about 50 mph and were much more intense - so different - as a result I did not look to this.  Any thoughts/experience on this option.

When I replaced the transmission, I removed the driveshaft.  Two things could have happened.  (one it might be 180 degrees out - and two I inadvertently pulled a cap off of one leg of the rear U-joint, but none of the needle bearings came out and it reassembled easily)  I had vibrations before this, but I wonder if I just replaced one vibration with another. 

Something other than the driveshaft.  I have a spare set of tires and can swap those on to rule out an issue with the rims and tires (I have not done that yet).

My thinking is to do a few more tests, maybe see if I can place a camera to look for the vibrations while driving.  Then I am wondering about tires, rotating driveshaft, balance, and then u- joint.  But I thought I would send a note to the forum in case someone has a better plan (or can rule out something or identify something from my description).

Thanks
 

[RallyeMike]

You should be able to define if it is tires or drive shaft by running the car in a lower gear. If the vibration is strong as typical at a lower gear (and lesser speed) than it is not the tires.

Check the U-joint for slop by trying to move the drive shaft while in the car. Replace any sloppy U-joint. Don't worry if the yoke wiggles slightly on the trans output shaft. It's supposed to do that.

If those fail, take your drive shaft down to a drive shaft shop to make sure it is balanced and not bent. Its relative inexpensive to do.

[CRW-FK5]

As many probably know, I have been tracking down the source of drivleline vibrations.   I am trying to decide on a plan of attack to get rid of them and would appreciate any help or advice I can get

Driveline angles:  I had thought it was related to driveline angles (and some of it may have been), but now I have the transmission and the carrier parallel to within 0.5 degrees of each other.  The front angle is 3 degrees and the rear is 3 degrees in the opposite sense.  The angles were not correct at the start and the situation has improved.

Presently, the vibrations start around 60m mph and get progressively worse at higher speeds.  I have 27 inch tires and 4.30 rear so the propeller shaft is spinning fast.

My thoughts are as follows:

I wonder whether it is worth having the driveshaft balanced.  It was a new driveshaft with the install from Hurst drivelines.  (I ask because I have had an issue with another driveshaft that was cured with a balance.  The vibrations there came on about 50 mph and were much more intense - so different - as a result I did not look to this.  Any thoughts/experience on this option.

When I replaced the transmission, I removed the driveshaft.  Two things could have happened.  (one it might be 180 degrees out - and two I inadvertently pulled a cap off of one leg of the rear U-joint, but none of the needle bearings came out and it reassembled easily)  I had vibrations before this, but I wonder if I just replaced one vibration with another. 

Something other than the driveshaft.  I have a spare set of tires and can swap those on to rule out an issue with the rims and tires (I have not done that yet).

My thinking is to do a few more tests, maybe see if I can place a camera to look for the vibrations while driving.  Then I am wondering about tires, rotating driveshaft, balance, and then u- joint.  But I thought I would send a note to the forum in case someone has a better plan (or can rule out something or identify something from my description).

Thanks
 

You mentioned "it might be 180° out".  If you meant that when you reinstalled the driveshaft you weren't sure if you put it back in the exact same orientation relative to the yoke tha  shouldn't matter.

Are you the same size universal joints on each end of the shaft (both large or both small)?

Have you isolated it to something other than trans?  In other words, is it vehicle speed related or engine rpm related?

[XH29N0G]

Thanks for the feedback. 

I can answer some of the questions:

You should be able to define if it is tires or drive shaft by running the car in a lower gear. If the vibration is strong as typical at a lower gear (and lesser speed) than it is not the tires.
Check the U-joint for slop by trying to move the drive shaft while in the car. Replace any sloppy U-joint. Don't worry if the yoke wiggles slightly on the trans output shaft. It's supposed to do that.
If those fail, take your drive shaft down to a drive shaft shop to make sure it is balanced and not bent. Its relative inexpensive to do.

The vibration appears to be speed dependent only (lower gear, higher gear, neutral, and clutch depressed do not change it).  There used to be a decrease on acceleration and decrease on deceleration (uphill and downhill were different) but that was before I corrected the angles.  I tried wiggling the U- joint (it is all the same size cups) and it doesn't wiggle. 

You mentioned "it might be 180° out".  If you meant that when you reinstalled the driveshaft you weren't sure if you put it back in the exact same orientation relative to the yoke tha  shouldn't matter.
Are you the same size universal joints on each end of the shaft (both large or both small)?
Have you isolated it to something other than trans?  In other words, is it vehicle speed related or engine rpm related?

Yes, I did mean that I wasn't sure when I put the u joint in the rear yoke whether it went in with the driveshaft in the same orientation or 180 degrees out.  The teeth on the slip yoke have a notch for my transmission so only fit in one way. I didn't think it would make any difference, but it was one of the few things I could think of.  (U joints are the same size - both large).  The vibration only depends on the speed of the car  (The RPM is something like 3000 when it is 1:1 through the trans).  The one thing I have not checked with the most recent configuration is the uphill/downhill test.

From reading some other threads, I am beginning to think it could be the balance on the driveshaft.  There is a truck place nearby that balances them, and I think they are good so I will probably take it there in a week.   

[cdr]

I would get the shaft checked for straightness & HIGH speed balance, on mine I had a 4" diam aluminum shaft built. 

[XH29N0G]

thanks.  I am hoping my assessment of the shop I will go back to is right.  they mostly work on big trucks, and last time made it really smooth

[CRW-FK5]

thanks.  I am hoping my assessment of the shop I will go back to is right.  they mostly work on big trucks, and last time made it really smooth

Does the vibration go away above some (reasonable) RPM level, get worse, or stay about the same?  Are tires balanced?

[XH29N0G]

So far, the vibration starts at 60 mph and increases in intensity (I think linearly but have no way of quantifying that) up to 80 mph.  I am in an urban area so running at any higher speed would not be prudent.
The driveshaft RPM is in the neighborhood of 3000-4000 at these speeds. 

The vibration is fairly high frequency, and does not feel like the 700 to 900 rpm I would expect for the tires.  I have not swapped the tires back to the original set, but the set I have on there is balanced and has about 3000 miles on them. 

I just put a dial micrometer on the center of the driveshaft (I don't have a magnetic set up, so that was where I could bolt it to an exhaust pipe and make it work), and see less than 5/1000 deflection on a full rotation of the driveshaft.  I think this indicates that the driveshaft is straight and that the alignment of the u-joints is OK.

Right now, I am thinking of balancing the driveshaft, but if I get some other brainwave, or burst of energy, I might try switching back to the older set of tires to check for a change.  But my guess for now is the next step should be balancing the driveshaft and slip yolk assembly.

[Nacho-RT74]

I'm having same issue since EVER! but vibration begins softly and some harmonic ( somethin like RRRrrrrrRRRRrrrrrRRRRrrrrRRRRRrrrrr  ) maybe at 60 or 70 MPH then increases and becomes constant, but still harmonic, then becomes constant and AWFULL at 110 MPH or so... I haven't being able to get more than 110 MPH EVER because that. Even my rearview mirror begins to shake!!!

I'm pointing out to some problem at tranny or tranny tail, because I'm able to feel it down the tunnel. I have changed EVERYTHING allong the years, not because this, just because I have being upgrading, and allways keeps this same failure. Diff wheels, Diff tires, diff Axle ratio and carrier ( open and now SG ), diff crossjoints and in fact even diff rear driveshaft yoke, Diff engine setup ( stroked so diff crank ), diff TC... Only gets me to the driveshaft itself and something into the tranny tail.

The machine guy who made the yoke change job told me he never noticed any unbalancing problem on driveshaft, but maybe needs to take it to a more specific driveshaft shop now.

I'm to install also the counterweight to the tranny tail too. Never have got it since I bought the car.

Sorry if this is considered a highjack, but trying to track same issue, and want to keep an eye on this

[XH29N0G]

Nacho, not a hijack.  Sounds like a similar problem.  I am just about to pull my driveshaft and can see if the rebalance makes a difference.  My issue might not be the same as yours, but who knows.

[RECHRGD]

Go ahead and get the driveshaft balanced, it's no big deal.  If that doesn't stop it you may have to do what I did when chasing this problem for years after installing an OD unit.  Balance the driveshaft while it's on the car.  Google it, there's lots of good info out there.  Get some big pipe clamps and go for it.  It took me all day.  It can be done with the rear end up on jackstands, but a lift makes it much easier.  Good luck.......

[XH29N0G]

Thanks.  Dropped it off and picked it up today.  It won't be till the weekend when I see it.  The guy at the shop moved the weights and said it was out of balance.  Last time the did a good job, so I am hopeful this is the solution.  I will let you know after the first test drive.

[XH29N0G]

First test drive was this morning's rush hour so only made it to 70 mph, but it is much smoother.  This weekend I will do more tests and give what I hope will be the final update.  

I had read that sometimes even new (advertised as balanced with the most modern techniques) are not balanced.  

When I went in, the person at the shop asked about the vibration and if it went up and then down, or just kept getting worse.  My most recent vibration just kept getting worse as speed increased.

[Nacho-RT74]

 

[XH29N0G]

Nacho-RT74,

It is almost all gone.  smooth at 60 and 70 (even 75), but I can still hear something (not feel it) come on in the mid 80 mph range.  I am sensitized to it, so I do not know if I would pick it up if I were not looking.  I assume it will increase at higher speeds, but have not looked into that.  I am  spinning a 4.30 rear, so the driveshaft is moving pretty fast event at 80.  You can convert that to what your gear ratio would spin.  My total cost was $40 for the balance and that made the biggest difference.

[cdr]

you might do some reading on terminal velocity of a drive shaft,  weight , diam , length , rpm !   What is the gear ratio of the trans in high gear ?

[XH29N0G]

you might do some reading on terminal velocity of a drive shaft,  weight , diam , length , rpm !   What is the gear ratio of the trans in high gear ?

Thanks, I will. 

My trans is 0.64:1 in high gear.  At 80 mph, I think I am spinning it just over 4000 rpm (27 inch tire 4.30 rear). 

The driveshaft is steel ~52 inches long and 4 inch diameter, which I think puts its critical speed well above where I am or ever plan to go.  One table had it at 8800 rpm which would be above 160 mph. 


My angles are matched, and are 3 degrees equal and opposite.   The possibilities I can think of are: I didn't get the angles right; the driveshaft still is a little out of balance; or something else.  It is very close right now though and I appreciate all the help and feedback I have received in sorting this out. 

[Nacho-RT74]

Ok, My car is totally dissasembled at this moment. Hoping will be finished by the end of this year or maybe beginning next year. So will check the driveshaft balancing, which is the stock one.

I don't think angles will really afectt, because wouldn't have any sense the existence of a piece that alows variations for that assembly. Remember as soon ypu sit on your car, will change. Every time you give gas, these angles changes. When you fill your trunk with anything, or get passengers in!

[XH29N0G]

Ok, My car is totally dissasembled at this moment. Hoping will be finished by the end of this year or maybe beginning next year. So will check the driveshaft balancing, which is the stock one.

I don't think angles will really affect, because wouldn't have any sense the existence of a piece that allows variations for that assembly. Remember as soon ypu sit on your car, will change. Every time you give gas, these angles changes. When you fill your trunk with anything, or get passengers in!

Then it will be great when you have it back together.  I changed the transmission so the geometry changed (and last week when measuring angles, I put all of the dumbells I owned (weights not people) in the footwell of the car to see if the weight was the problem).

With the original set up, the only time I had the driveshaft vibrate was because a balancing weight had come off.  It was fine one day, and it vibrated like crazy the next.   

[Danny Gutierrez]

I am having the same problem. My vibration starts around 40 mph and gets worse the faster I go. I pulled the drive shaft and the yoke was burnt blue on only one side. Got a new yoke and had the shaft balanced. My driveshaft guy suggested that the tail shaft might be bent. It's driving me nuts!

[XH29N0G]

I am having the same problem. My vibration starts around 40 mph and gets worse the faster I go. I pulled the drive shafts and it was burnt blue on only one side. Got a new yoke and had the shaft balanced. My driveshaft guy suggested that the tail shaft might be bent. It's driving me nuts!

I see your other post.  I wonder if you can measure runout on both ends of your driveshaft to see if it is rotating off center.  I am one on here who gets more advice than I am able to give, so others may have a better suggestion.  I have only tried to measure runout once, I used a micrometer (the one I used to degree my cam) and mounted it to the underside of the car and then rotated the driveshaft by rolling the car.  I have seen demonstrations of measuring runout on the web with the car on a lift.

I know these vibrations can be a nightmare to find and fix.