Driveshaft Vibration?

[Cory J Tate]

Hi Everyone, I have a 63 convertible that I am trying to chase down what I think is the drive shaft vibration. I have tried to search and read all of the articles in here that are related to that but would still like some additional insight before I go one way or the other to correct it. 

I have the car at a shop right now, and they seem to work on a lot of the early 60's Cadillacs. They have a 60 & a 64 in the shop right now, so I feel like I'm probably in the best place that's available to me to do some work. 

The vibration I get is at higher speeds, 45+ and continues to get worse the faster I go. 

I can hear/feel it change when I am accelerating vs coasting vs decelerating so I'm less inclined to think its tires or hub related issues. The other factor is that the vibration pulsates in a rhythm, its not a consistent shake like a bent rim or tire that's out of balance.    

The shop pulled the driveshaft and was familiar with the resistance they should feel in the CVU joints (similar to Jason's Video) and he says its tight and "pops into place"   

They had the driveshaft rebalanced and removed some weights. Put the car back together, drove it, and there was no change. 

They did have some concern that the rubber that's pressed into the shaft was rotting and could be causing imbalance at high speed. He said I can remove that rubber but may end up with some noise when going between forward and reverse. Any thoughts on that?

Last year while changing the seal around the slip yoke, I loosened that rear trans support trying to get the drive shaft out and so I may have messed up the geometry there... but from the articles I've read about shimming the rear of the trans, that's more likely to cause problems at low speed? 

I guess I am at a point now where I need to decide my next step in solving this... 

It seems like finding a good OEM driveshaft is the best way to fix these vs trying to cut/splice/rebuild this one. But how hard is it to find a GOOD original one? 

Also, do ya'll think that the rear trans mount being out of line could be the reason? The shop says there is very little variance possible from just loosening it and then tightening it; but is that enough to throw it all off? 

[24ro8f5mbs2jc]

I had vibrations. Did everything including change of rear axle. In the end it was a rebuild of the CV-joints (again) and a full re-balance in a lathe that solved the problem. The shop do a lot of work on dragsters so I guess they really knew what they were doing.

Everything = replaced wheel bearings, replace all rubber rear and aft, renew centre bearing, re-built CV-joints, full overhaul of gearbox and some more that I forgot.

[Cory J Tate]

Thank you Anders! When you say that you rebuilt the CV-Joint again, are you keeping the original one and rebuilding the ball/spring/joints -OR- did you replace that original CV with a new Double Cardan Style joint? 

[d185bff8eebf41ee9e2bda89838b7799]

I am in the works of building a 1 piece so when it comes back from the lathe I will let you know how it works!

[Cory J Tate]

Dive shaft Fixed!  It turns out that the driveshaft (for an unknown reason) was "running un-true". The guy said that basically it was not 100% straight and that's what was causing the vibration.   

He was familiar with the rear CV and said that he could rebuild it if necessary, but in this case the CV's were still tight and did not need serviced, it was all in repairing the driveshafts themselves. 

 I picked the car up last week and for the first time in over a year I could finally get it up-to 75mph and enjoy it. No Vibration!!   

[Cory J Tate]

Great point! I'm not sure how many people are in Denver area but that's where this shop is. 

Its called Dons Garage 

https://donsgaragedenver.net/

When I took mine in, I was nervous with it being a new place that I'd never been too... but they had a 1960 Deville hardtop in there that was the same color scheme as mine including the white top; it was getting a complete overhaul on the trans and they had a 64 coming in the following week for some work, so I did feel better that not only were there other classics, but specifically other Cadillac's!   

When I went to pick mine up they had a 59 impala on the lift, and a few older trucks so they seem to have a sweet spot for the older vehicles.