Driveshaft help...

I have a '66 Caddy Sedan DeVille, 429 Auto (I think thats a turbo 400?), 78,000 miles. Nice car... its had a pampered life.

It developed a squeak and a very minor vibration under a load, put it up in the air and found one of the rear spiders starting to lock up. This thing has a constant velocity joint front and rear as opposed to a simple U joint set up. It appears that there is a large sping loaded ball bearing inside this thing, so I thought I would take it to a local drive shaft repair center here in Kansas City instead of trying to replace the spider myself. They called a few days later and said the rear CV joint was shot, that it should be replaced (for just a small amount more ) and I told them to do it. I got the driveshaft back and tried to install it on the car and it had an incorrect rear flange on it. The new CV joint had the wrong bolt pattern, it may have been for a different model Caddy or a truck or?

I sent it back and they ended up using the rear part of my old CV joint because it has the proper flange on it, so now I have kind of a Frankenstien half and half CV joint... front half new.. rear part old. I put it in the car and the squeak is gone but now it shakes violently under a load. RPM's or speed doesn't seem to affect it, you can go fast under light throttle and it doesn't shake, but if you floor it you can mix paint.

I put the car back up in the air and checked what I could. Motor mounts and ****** mount are good. All the control arms to the rear diff have good busings in them. The car has brand new shocks. There appears to be no play or strange noises in the rear end and it has pleanty of lube in it.

I yanked the driveshaft back out and and took it back down to the driveshaft place and they are telling me there is no problem with it, that I must be on drugs or something..

Is there anything I am missing here? Help me out... what else should I look at before I start to go postal... I'm not interested in bashing the guys at the driveshaft place right now... I want to find the problem

Tomo

 

Could be a couple things.
First check the driveshaft carefully for any dents or hammer marks. Very common for an inexpirienced person to "miss" and hit the tubing or worse put the tube in a vise and ...........

Second make sure all or the jonts have full travel and are free from bind and or a "hitch" feel. Check and make sure all the circlips and or snaprings are in properly.

I wouldn't worry about them using the old flange , unless it was damaged before or during install. make sure you have it seated against the mating flange properly. (its in front /back correctly?)

Other than U joint going bad or CV center going bad a driveshaft doesn't go bad by itself. Check carefully the slip joint if that is worn / loose AT ALL that could be amplified by new joints. Fairly common issue. Unless a driveshaft tube is dented or twisted itself doesn't change.

When all this work was done did they balance the driveshaft?
Are the two ends in phase? If they took it apart at the slip and re***embled it out of phase it will vibrate.
Hope this helps , if not keep me posted. ( I work at a driveshaft shop)

 

Thanks Gr8lite!!

They did balance it... and they have rebalanced it this time. It is still at the shop and I will pick it up Monday. Before I ever took it down there I had painted all the joints ect to be able to see if it was "in phase" when it returned... but now that you mention it the new part of the rear CV joint would have no paint mark, and that part is welded to the driveshaft tube so there is a possibility it could be out of phase, I will most certainly check that.

You speak of making sure that all the joints have full travel and that there is no hitch feel to it. Before I ever started this I noticed that both the front CV joint and the rear CV joint felt as if they were spring loaded, meaning as I moved them through their rotation they would be actually pushed off to one side or the other, If I let go the CV joints wouldn't stay straight. I thought this was normal... they both had pretty much the same "feel" to them. When I got the driveshaft back from the shop the rear CV joint no longer did that, you could put it in any position and it would stay there. Is there a spring in there... maybe resting on that large ball bearing. I now wonder if they left a spring out when they rebuilt that? Or does this even matter?

The tube itself isn't dented or bent... and the only slip joint is the shaft end that slides into the tail housing of the ******, and that slides freely. It should... I have pulled it out of the car 3 or 4 times now .

Thanks again for your reply.. any info is helpful and something to check...

Tomo

 

CV joints are supposed to "snap", sounds like they screwed up the rear joint.

 

you said that if you floor it you could mix paint. o you mean from a standing or slow start? If so, you could be mistaking wheel hop for drive line shake. How does it feel at 80? 60? 40?

Either way, Unless they reduced the price, I would be insisting they replace the entire joint, even if they need to order parts.

 

If I put a load on the drivetrain, such as using full throttle or even accelerating up a hill it vibrates, at any speed. I can pull away from a stop sign and if I use probably more than 1/3 throttle it vibrates, or I can be coasting at 50 mph and there is no vibration. Its not wheel hop... I can feel this vibration in the floor boards and seat more than the steering wheel. So... just to sum up... if I use no or very little throttle at any speed it doesn't vibrate, if I put my foot into it (at any speed) it will start to shake. I don't think its a balance issue, I think its a CV joint problem... but I'm not a driveshaft expert... so I'm just fishing for advice and ideas...

Is there anyway I check this myself? I have a lift and can put it up in the air and power brake it but what would this tell me? Or are there other tests I could do??

Right now it appears that I already know more about driveshafts than the people I am dealing with . I just want to try and make sure its the driveshaft and nothing in the car before things get nasty...

 

Get it solid on jack stands and put it in neutral so you can move the shaft by hand. Feel for any slop in any direction. Also disconnect it at the rear and check your pinion yoke to make sure you haven't lost the bearings there. If you find slop anywhere, fix it. Maybe choose a new shop if you don't expect this one to stand behind their work.

 

I have a lift... I have put the car in the air and checked for slop... ect. and have none. This driveshaft has a flange that bolts to a flange (pinion) on the rear end. There is no slop in the pinion.

When I get the driveshaft back tommorrow I think I'll put the car up in the air and see if I can duplicate the vibration by power braking it. Maybe I can pin it down. If I can eliminate the ******, the front CV joint, and possibly the rear end from the candidates causing the vibration that would pretty much leave the CV joint they worked on....

You would think that a city the size of KC would have more than one driveline repair shop but it appears they don't.

Thanks again for the input.