VIBRATION!!! I FOUND IT!!!!!!

[flyinlow]

When you ran the car without a drive shaft , did you have a spare yolk in the GV output shaft?

Is it loose like a 727 tail shaft without a yolk installed?

Did you try braking lightly ,while maintaining speed , in your vibration range to load up all of the splines. (driveshaft and axle)

Companion flange nut tight?

Just a couple thoughts. Good luck!

[G Force]

Well my car is still in the shop. The Mechanic suggests and is ordering a Precision made drive shaft and is changing the Universal joint at the rear end to match that at the GV side.
This will be the 3rd different drive shaft going into the car.
From what I understand, when a drive shaft is built it is not perfect and their are weights that are usually added to help balance the unit.
This new drive shaft will be built at a much higher quality standard.
The weight and mass of the drive shaft itself also have an affect on its performance.

[speedfreak68]

Well my car is still in the shop. The Mechanic suggests and is ordering a Precision made drive shaft and is changing the Universal joint at the rear end to match that at the GV side.
This will be the 3rd different drive shaft going into the car.
From what I understand, when a drive shaft is built it is not perfect and their are weights that are usually added to help balance the unit.
This new drive shaft will be built at a much higher quality standard.
The weight and mass of the drive shaft itself also have an affect on its performance.

Not to hijack this thread but where do you recommend getting a drive shaft from? and also how bad are they $ wise?
Thanks
Martin

[G Force]

Well the new Precision drive shaft was custom made and installed along with the new universal joint and there is absolutely No difference.
The vibration is unchanged.

[RECHRGD]

Well the new Precision drive shaft was custom made and installed along with the new universal joint and there is absolutely No difference.
The vibration is unchanged.

G force, I feel your pain.  Most of my posting on this subject has shifted to the thread I posted in the engine, transmission section praising GV's efforts to find the issue.  I took my driveshaft (2nd one) to another driveline shop and had it checked.  He found a small vibration up front and fixed it.  I thought that maybe my troubles were over, but it was not to be.  Although a little better, the vibration was still there.  I spent the better part of a day taping weights to various points of both the front and rear of the driveshaft and taking the car up to speed while jacked up on the lift.  I could make it a little better or worse, but could not get it fixed.  GV wants me to do the same thing using large pipe clamps, (which I have done and will do again) but I'm having doubts that I'm ever going to get this thing to not vibrate.  I had to walk away from this thing for a couple of days, but may get back out to the shop tomorrow for another try.  I'm getting very close to the point of just yanking it out of the car for good.  If I can't fix it by "fine tuning the shaft on the car", the only thing left would be to put out big bucks for an aluminum driveshift.  Lighter weight might be enough to change the dynamics facilitating a fix.  However, if that failed to work, I would most likely fill the car full of bullet holes and push it over a high cliff.  Bob

[Sublime/Sixpack]

  However, if that failed to work, I would most likely fill the car full of bullet holes and push it over a high cliff.  Bob
[/quote]

I know you're joking, but you are starting to worry me a bit. Hang in there.

[elacruze]

Wish I was nearby. This is the type of problem I can bury myself in (especially if it's not my car, sorry)

Anecdote; I was young and dragged an unproven race bike from Detroit to Daytona for speed week, and it wouldn't run. It was a Honda, and the Honda Factory had their team there so I found their world-famous tuner and asked for help.

He said; "Son, there's no magic in there. Something isn't put together right. Find it."

That seemed a bit harsh at the moment, but it got my head on straight about it. I found the problem which in this case was self-inflicted but not too obvious.

[G Force]

Well the new Precision drive shaft was custom made and installed along with the new universal joint and there is absolutely No difference.
The vibration is unchanged.

G force, I feel your pain.  Most of my posting on this subject has shifted to the thread I posted in the engine, transmission section praising GV's efforts to find the issue.  I took my driveshaft (2nd one) to another driveline shop and had it checked.  He found a small vibration up front and fixed it.  I thought that maybe my troubles were over, but it was not to be.  Although a little better, the vibration was still there.  I spent the better part of a day taping weights to various points of both the front and rear of the driveshaft and taking the car up to speed while jacked up on the lift.  I could make it a little better or worse, but could not get it fixed.  GV wants me to do the same thing using large pipe clamps, (which I have done and will do again) but I'm having doubts that I'm ever going to get this thing to not vibrate.  I had to walk away from this thing for a couple of days, but may get back out to the shop tomorrow for another try.  I'm getting very close to the point of just yanking it out of the car for good.  If I can't fix it by "fine tuning the shaft on the car", the only thing left would be to put out big bucks for an aluminum driveshift.  Lighter weight might be enough to change the dynamics facilitating a fix.  However, if that failed to work, I would most likely fill the car full of bullet holes and push it over a high cliff.  Bob

The mechanic working on my car has spent countless hours adding large hose clamps with weights onto the old drive shaft as well as changing the pinion angles by using a jack stand while the car was on the lift. There were all varying degrees of changes to the vibration but there was not one time that there was no vibration.  The Drive shaft that is in the car now is the third one and is considered a high end  precision made shaft. This precision drive shaft has made No change to the vibration levels.
The mechanic noticed that while driving on the freeway at 60 MPH with the GV overdrive unit OFF,, the vibration is strong VS driving on the freeway at 60 MPH with the GV overdrive unit ON,,, the vibration is very much reduced (still there but not as strong). This would suggest that the variation is caused by a RPM change. The mechanic is now suggesting that it could be a vibration in the transmission or converter. I have changed the transmission converter in the car multiple times (3 to be exact ) The mechanic says we should take the transmission and converter out of the car and put it on a dyno to test it independently for vibrations.
Trust me,, I know exactly how you feel when you talk about bullets 

[RECHRGD]

I FOUND IT!!!!!!  I FOUND IT!!!!!!!   I took one last try at it using the pipe clamps.  I started at the front of the driveshaft and methodically tried different positions and noting if their was any change, good or bad.  I finally hit a spot where there was some noticeable improvement.  I put a penny under the clamp screw and it got a little better.  I then went to the rear and went through the same thing until BINGO, and it was gone.  I called GV and they were surprised that it took weights on both ends, but hey, whatever works.  So anyway, as happy as I am, I still don't get it.  I had to take a perfectly balanced driveshaft and basically unbalance it to smooth things out.  If I didn't have a lift and plenty of time I never would have found it.   Bob

[mauve66]

soooooo, when i finally get mine running i can tow it to your lift and see if the GV i put in 8 years ago is gonna have any problems..............
burn out videos are now required.........................

[b5blue]

CONGRATULATIONS!!!!!! 

[mauve66]

so now you need to update the title of the thread

[squeakfinder]

   
         Good deal! 

[greenpigs]

Not to poop in the punch bowl but is it fixed or just got a bandaid? 

[bull]

Great news, Bob. So, now I'm curious how this can happen. Is the balancing method those guys used incorrect? Is it balanced until installed?

[ACUDANUT]

 I gotta see a picture of this

[tan top]

Great news, Bob. So, now I'm curious how this can happen. Is the balancing method those guys used incorrect? Is it balanced until installed?

  think because the OD trans  turns the drive shaft much faster than it would be with a normal trans , so needs to be more accurately balanced

[Cooter]

Stands to reason as the driveshaft spins at incredible speeds in OD...

[RECHRGD]

The driveshaft was in perfect balance.  With the added weight of the GV, shorter driveshaft and different angles the whole dynamics of the drivetrain is changed.  GV says that it is very common to have to "fine tune" the driveshaft after it is installed.  Why?  I can't answer that one.  It just seems to me that I had to unbalance it to make it smooth out.  And, no the driveshaft does not spin any faster with the overdrive.  It takes X amount of revolutions of the DS to go X mph regardless of whether the OD is engaged or not.  I'll try to post a picture of the installation later today.  Bob

[BrianShaughnessy]

Was this a steel or an aluminum driveshaft?    Specs?

[RECHRGD]

Was this a steel or an aluminum driveshaft?    Specs?

It's steel.  Aluminum may really be the way to go though.  I would think that the lighter weight may counter some of the effects of hanging an extra 40 pounds off the end of the tranny.  Bob

[greenpigs]

I think the aluminum ones are about 25lbs lighter than a stock driveshaft. I looked at them from a performance aspect and from what I gathered they don't offer much. What I mostly read was the motor can rev slightly quicker due to the reduced weight. I thought Hot Rod did a chassis dyno test on one a few years back and it gave a 3% gain. For about $250 more it might be worth it...if your trying to eek that last HP out.

[HeavyFuel]

Stands to reason as the driveshaft spins at incredible speeds in OD...

Ummm....the OD lowers the RPM of everything in front of it....and doesn't effect the RPM of anything behind it.

[ACUDANUT]

Great news, Bob. So, now I'm curious how this can happen. Is the balancing method those guys used incorrect? Is it balanced until installed?

  think because the OD trans  turns the drive shaft much faster than it would be with a normal trans , so needs to be more accurately balanced

The overdrive make it spin slower, or so I thought.

[Cooter]

The driveshaft was in perfect balance.  First off, nothing's perfect 



And, no the driveshaft does not spin any faster with the overdrive.  It takes X amount of revolutions of the DS to go X mph regardless of whether the OD is engaged or not.  Second, I was refering to the driveshaft spinning at high speed due to the fact that the major limiting factor was your engine's RPM before with the gears and 1 to 1 in high gear....Now, with the OD, you can drive that car at incredible speeds with the VERY same gearing and engine but at a lower RPM on the engine...Therefore, the driveshaft is spinning ALOT faster when at say 80 MPH with 3:23 gear than at 60 MPH...The lower engine RPM causes one to drive his/her car at higher and higher speeds... Cause they can...