C1 Driveline Vibration

[Dave H.]

Thanks to all that responded to my earlier post.

We rotated the driveshaft 180 degrees, replaced one of the U-joints, shimmed down the transmission mount 1/4 inches, and rebalanced the tires. None of this made any difference.

Remember, the problem started when I replaced the T-10 with another T-10, using the same output shaft. Before that, there was no vibration at all. So I find it hard to believe that the driveshaft is the problem. I suppose it might have been dropped, but I don't see any evidence of damage.

It is possible that the problem is in the alignment of something in the transmission, even though the vibration sensation definitely comes from the rear of the car and appears to be in time with driveshaft rotation? Also, the transmission appears to be working fine... there's only a little vibration through the shifter, more in the seat of my pants.

Is the answer to have the driveshaft balanced anyway?

Thanks,

Dave.

[Joe L.]

Re: C1 Driveline Vibration

Dave------

I was very dubious that rotating the driveshaft 180 degrees would do any good for you. It's worth a try, of course, but in the vast majority of the cases, it's not going to solve anything.

I would DEFINITELY recommend that you have the driveshaft balanced. Have it balanced completely assembled with u-joints and transmission yoke. I think that will solve the problem. Actually, driveshafts should be checked for balance anytime that the u-joints are replaced. There's no reason to believe that the new u-joints + the driveshaft will be in the same state of balance as the previous u joints + driveshaft.

One other possibility: what is the condition of the T-10 that you installed in the car? Is it freshly and completely rebuilt including the extension housing bushing? If not, are you sure that the extension housing bushing is in good shape?

[Anthony F.]

[Michael H.]

Re: C1 Driveline Vibration

Tony,

I think you're right on the money with the twisted/bent main shaft inside the transmission theory. It's not nearly as uncommon as you might think. In the 60's, I knew someone that did this to three B-W main shafts in as many months. A slight twist in that shaft usually also creates a slight bend and it doesn't take much of a bend to make the front half of the drive shaft run untrue. When it happened to the friends car, it also created quite a vibration.

Often, but not always, the splined end twists slightly also which sometimes makes it difficult to install/remove the drive shaft front yoke.

[Mike B.]

Re: C1 Driveline Vibration

Dave,

I don't recall if this was mentioned in the replies to your first post but I remember hearing about a case wherein many suspected the transmission/drive train as the source of vibration when it turned out to be a faulty harmonic balancer. I know that it would be a heck of a coincidence with switching out transmissions but stranger things have happened.