I've been chasing a vibration on decel for over a year and simply can't figure it out. I cross and go to neutral, kill the engine and a nasty little vibration starts. It lasts for a second or 2 then stops. I'm afraid it's going to star tearing stuff up. I found pinion angle was at zero after being worked on by chassis shop. I adjustment and thought that fixed it but is doing it again after a few passes. I didn't do it every pass but seems to be getting a little worse. I'm considering changing u-joints even though they feel fine. It feels like a driveline issue to me. It seemed to have started right around the time I installed my new transmission but can't say for sure it was exactly then. Transmission guy says nothing he could think of with trans would cause this.
I had an issue with this before and ended up being yolk wasn't engaged far enough in the transmission. It sets about 3/4" from being fully bottomed out. At 1.25" it vibrated, has been good at 3/4"
I also had a wishbone added to the car the at same time.

This message has been edited. Last edited by: inferno camaro,

It may sound a little hilljack, but put it on stands and see if you can duplicate the vibration.
If yes, take the wheels and tires off and try again.
Any chance there is a way to put an eyeball on the rear gear.
Pinion bearing?

Need to find it and kill it.

It has had a new center section and new axle bearings since it started with no change.

What else have you done/changed so far?

If the vibration only transpires while the car is decelerating and you are certain the vibration is located in the rear of the car, then think about what only happens while the car is decelerating.

(1) The drive shaft angle becomes substantially more negative.

(2) Nothing else, since you've eliminated the problem as a wheel bearing failure, a bent axle, a universal joint failure, a driveshaft out of balance, a differential (ring and pinion) failure, a differential bearing failure, (new third member) or a wheel/tire balance issue the only thing that does happen is that the driveshaft angle changes.

Incorrect rear springs on a leaf spring car can create a similar vibration on deceleration.

My question: What are the rear springs rated at?

Bob

Have you taken the driveshaft to Chuck's yet?

quote:

I'm considering changing u-joints even though they feel fine. It feels like a driveline issue to me.

Does it vibrate if you leave it in gear and let it coast down, then shut off?
I.E.> keeping the driveline loaded

do you feel it in seat of pants or whole car.in seat my vote is drive line related. whole car tire related.

My dragster would do something similar with my previous set of slicks. Just a short vibration fairly early in the decel process.

I've checked pinion angle, driveshaft front yolk angle, checked all heim joints, checked that the wishbone isn't in a bind. I'm debating changing the tail shaft housing with my spare trans to eliminate any issue with roller bearing in the trans. It feels fine, its not loose and feels smooth when turning it. The slip yolk has no funny wear on it.

Rear springs are 100lb.

I haven't tried leaving it in gear, it loses oil pressure almost immediately upon deceleration.

I would say more of the car vibrating, I wouldn't call it a shake definitely more of a vibration.

Interesting about the tires. I bought a set of smaller tires that I have mounted on another set of wheels and didn't really notice it with them but were only on the car a couple weeks. I will take them with me next time and try them if it's still doing it.

I took the u-joints out and they look and feel good. I did find the small plastic disc that sets under the needle bearings is broken in one of the caps on the rear of the driveshaft. No idea if that could cause it but had a guy tell to check them because he had an issue with one of the discs missing once and it vibrated violently.