Drivetrain vibration problem

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Moparmal

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I have a drive train vibration atm, and Im trying to isolate whether its a Uni, pinion angle or an unbalanced drive shaft.

My pinion angle seems to check out within spec - at least as per Dr DIffs recommendation - but I have the following problem -

1/ The drivetrain vibrates quite heavily at low speed, either coasting down at slow speed to the stop lights - travelling at a constant 20 mph, or accelerating from a standstill.

2/ The vibration decreases significantly at around 45 mph, and returns at a much higher frequency at around 55 mph.

3/ The vibration does not magnify when I lift off the throttle at high speeds. (So the pinion dropping doesn't make the problem worse)

I have changed the rear uni but it had little effect.

Just wondering if you think its more likely to be a front uni (which doesn't feel worn at all) or a pinion angle problem, or a drive shaft issue?

Happy Easter to you and yours....
 
My opinion. Remove the drive shaft, have it balanced w/ new joints front and rear. There is also a bearing in the tail shaft of the A727 (not sure about 904) that could cause your vibration problems. You could replace that also. Good luck.
 
so the opinions seem to be a bit "each way" atm - I guess this is going to be a search and destroy mission?

I was hoping there'd be a tell-tale sign in what I explained that would lead me to fixing the problem the first time........Am I expecting too much?
 
Its an old car brother, nothing is going to be easy. lol

Chryslers quality control was never that great. There old driveshafts were built ok at best. Most of us are upgrading our Horse power, and expecting the old parts to keep up. For example going from a 318 to a HiPo 360. The 318 DS was balanced for the rpm's of a 318, not the higher rpm's of a HiPo 360.

Long story short get the old drive shaft/u-joints balanced. 8)
 
well I got it sussed - I swapped the drive shaft 180 deg about, so the weights were towards the rear of the car, and 98% of the vibration stopped!

I can now enjoy my new diff!!
 
Had the same problem with my Dart. The factory driveshaft which is .060 tube thickeness give or take a few thousandts couldn't handle the additional torque that my stroker put out and it wasn't long before the vibration got worse. At first it was very minor and I was chashing my tail to figure out wtf was going on. I had the driveshaft balanced in the very beginning of the build along with new u-joints so I never gave the driveshaft a thought. I had all the tires rebalanced and they were fine. Finally I went back to the driveshaft and had it rechecked. Sure enough it was way out of balance to the point it couldn't be balanced. I think one to many burnouts had a little something to do with it if you get my drift. Had a new shaft made with .087 tube stock and everything is smooth again. The factory shafts just weren't that strong, at least on some of the Abodys.
 
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