Nasty Vibration

[Adger Smith]

Rear bushing in tranny or main shaft bearing.

[Darrin Christen]

Had a similar problem years ago. I had the drive shaft rebalanced, changed the bushing in the trans tail shaft housing, and also had the front and rear wheels rebalanced. Problem was still there, bad vibration about the last 300' of the track. Ended up breaking the trans case across the bell housing. I put a new Dedenbear trans case in the car and the problems was still there. By this time the rear tires needed replacing and bingo the problem went away. Smooth as glass with the new tires. Before this problem started the car had sat in the garage for two months while freshing the engine. I had neglected to put the car up on jack stands and I guess the rear tires got flat spots. Won't make that mistake again.

[Ed Carpenter]

Mike I had the same thing last year. I could not hold the shifter in high gear. Pilot bearing came out in pieces when we dropped the can. Ed

[Mike Voth]

Originally Posted by deuces wild

Mike I had the same thing last year. I could not hold the shifter in high gear. Pilot bearing came out in pieces when we dropped the can. Ed

Another good suggestion. We'll find out tonight. Thanks, Ed. Coming up to Tulsa this weekend?

[Tracy Robbins]

I had a similar situation when a couple of bell housing bolts had backed out earlier this year, sounds simple but it can happen.

[Mike Voth]

Originally Posted by Darrin Christen

Had a similar problem years ago. I had the drive shaft rebalanced, changed the bushing in the trans tail shaft housing, and also had the front and rear wheels rebalanced. Problem was still there, bad vibration about the last 300' of the track. Ended up breaking the trans case across the bell housing. I put a new Dedenbear trans case in the car and the problems was still there. By this time the rear tires needed replacing and bingo the problem went away. Smooth as glass with the new tires. Before this problem started the car had sat in the garage for two months while freshing the engine. I had neglected to put the car up on jack stands and I guess the rear tires got flat spots. Won't make that mistake again.

Yeah, that's the reason the tires where changed before we made any runs at Denver. Thanks, Darrin.

[Jim B]

I really can't explain the driveshaft change and temporary vibration reduction having anything to do with what you have going on in the pressure plate but pay attention to Adger. If it's a failing eyebolt the plate will shift and cause what you found. (assuming the balance has changed) Definitely double check your finger height at whatever compressed thickness your disc is before reusing the pressure plate. I'm also assuming there is no centrifugal weight malfunction going on. Good luck....

[Casey Miles]

I went through a vibration problem with my car and it ended up being the universals that the drive shaft company installed were .040 too short in the sleeve that they sat in. Another words, if you messure the end to end of the universal, they might not fit exactly the way they are supposed to. I found it by going under the car, when getting myself back out, I grabbed the drive shaft and it went clunk. It was only .030 to .040 too short, but I went crazy looking for the vibration. The manufacterer was I believe Splicer and they were the 1350 solid joints.

Casey Miles
248H

[Jeff Lee]

I have heard of clutch surfaces being machined (improperly) at an angle and accounting for such out of balance numbers as you are reporting. You won't be able to see the problem either. It will also make your runs horribly inconsistent and a vibration. Measure all of your friction surfaces from side to side across 4 corners.
If you find your pilot bearing (I hope you use a bearing and not a bushing) is bad, I wouldn't jump to the conclusion that was the initial problem until I measured the clutch parts.
While on the subject, I've also heard of heat shields being ground but the back side remains warped from excessive heat. That will also cause problems because the friction side has inconsistent depths of material.
And while your at it, make sure your bellhousing to trans mounting surface is still parallel. Years of bolting down a trans can take it's toll on this. And re-dial indicate the run out of everything too.

[Mike Voth]

Originally Posted by Adger Smith

Rear bushing in tranny or main shaft bearing.

That's where we're going tonight, along with 3rd member. Thanks, Adger.