Driveline Vibration - Possible worn slip yoke?

[LDPosse]

I have some vibration in my driveline and I have not been able to figure out what it is. I am wondering if possibly a worn slip yoke could be the cause. I get vibration from like 45-55 MPH, then it fades some, then comes back around 70 MPH and gets worse as the speed increases.

The vibration is very little when accelerating. It is worse when decelerating. It is the worst when you are right on the line of accel/decel when there is very little load on the driveshaft.

I didn't really notice this until I swapped from 2.56 to 4.10 gears, I am guessing that the driveshaft speeds rarely got up high enough to cause this to happen. The trans (200-4r) has about 18k miles on it, the driveshaft has about 244k miles on it.

Is there a spec on how much the OD of the slip yoke can be worn?

Thanks!

 

[2quiktocare]

First thing I would do is get the drive shaft checked for balance by a driveline shop and check to make sure the u joints aren't off center. If that all checks out good, then I would suspect the differential since you didn't have the problem until the gears were changed. Just my thoughts. Mark

 

[LDPosse]

Originally posted by 2quiktocare
First thing I would do is get the drive shaft checked for balance by a driveline shop and check to make sure the u joints aren't off center. If that all checks out good, then I would suspect the differential since you didn't have the problem until the gears were changed. Just my thoughts. Mark

Thanks for the reply.

The driveshaft I am using is a shortened driveshaft from a '72 4-door skylark. It was shortened, had new spicer U-joints installed, and was re-balanced by a local drivetrain/driveshaft shop.

The axle is a chevy 12 bolt from a '69 chevelle, it has the stock posi and GM 4.10 gears (I opened it up to verify). I replaced the stock pinion yoke with a 1350 Pinion yoke from Moser. There is no play in the pinion yoke at all, and there is not very much backlash in the ring and pinion. With the wheels off the ground and the driveshaft disconnected, the pinion and the wheels turn very easily and smoothly. It also very quiet at road speed, just an ever so slight gear whine, it's quieter than my 2002 trans am's stock rear end with 3.42's.

I'm not sure what in the axle could be giving me this problem, unless it's possible that maybe the pinion bearing is on its way out, but wouldn't I notice that as the pinion yoke having free play? The frequency of the vibration seems way too fast to be a bent axle, or a bad axle bearing, etc etc.

I did have some vibration in the car with the old axle, but I didn't have problems until I was going 90+ MPH.

The only other thing I can think of, is that maybe my pinion angle could be off, but I don't know why it would be, the axle is out of an A-body, and I am using stock upper and lower rear control arms with it.

I will call the driveshaft shop where I had the work done just to see if they would take a look at the positioning of the U-joints to be sure it is correct.

Any further suggestions welcome.

 

[2quiktocare]

I would look at the pinion angle also then. You may have a slight enough difference to cause this kind of thing. At this point you can't rule out anything actually. It's simple to varify bent axles, but they would not go away and come back. You have one of those little gremlins that is gonna take some time of diagnosis to find it seems. Mark