wrd1972

iTrader: (12)

Here we are chasing vibes yet once again. I really dont think its T56 tranny related this time, feels like driveline.

I am replacing both u-joints tonight since one is not a genuine spicer although I am not encouraged it would help. The aluminum DS has not lost any weights and looks fine.

So I am wondering, could bad pinion bearings cause a vibe around 75MPH+ ?

A while back, my pinion preload was far too light and was making a strange noise when cruising at higher speeds when transitioning just on the gas and off the gas. Tightening this up help ed a good bit but the bearings were likely loose for a very long time.

Upon inspecting them, I did not see any obvious issues but in fairness, I dont know what to look for. Also I dont have any pinion whine or weird sounds like that. Vibe occurs on the road and on jackstands.

So can bad pinion bearings cause a rearend vibe?

bp m1009

iTrader: (2)

yes, is there any play up and down on the pinion? i had bad pinion bearings that vibrated a lot.

wrd1972

iTrader: (12)

When I inspected with the very loose preload, I detected a very small bit of up and down movement when I had the pinion support clamped in a vice. When I tightened the preload, i nop loger saw any movement but thats not to say that it cant.

I am really hoping that there is some funky wear in the bearings due to insufficiant preload that is causing this.

great421

iTrader: (1)

FWIW -

I get my Aluminum 3" driveshaft balanced once a year - when it bends (and it does bend, unlike steel, which just 'flexes' and then returns to its original shape) that bending causes my driveline to vibrate.

Just my $0.02...

wrd1972

iTrader: (12)

Update.
After closer eval of one of the u-joints, I now suspect wear. I also noticed that with the rear wheels off the ground, when you forcefully turn the rear wheels back and forth, I hear a what I would consider abnormal metallic clunking sound.

The suspect u-joint in question was actually installed last winter but it was not a Spicer part. It was a likely cheap Chinese **** part from the a discount parts house that I was forced to get because it was a Saturday and the Spicer shop was closed till Monday.

So after installing the new joint and rocking the wheel back and forth, that loud metallic clunk was greatly less obvious. I also while still on jackstands, I ran it up to 80MPH and the vibe was also significantly less than before. There is a very faint vibe still there at high MPH but I doubt it is of much concern and may even be considered normal.

I did not get to drive it yet because its been raining like Hell so it will wait till tomorrow. That said, I am very optimistic the issue is fixed. So the moral of this story is, only use Spicer u-joints.

wrd1972

iTrader: (12)

After a test drive, the vibe is gone. Definitely a bad u-joint.

autogeek23

iTrader: (13)

i also have bad vibrations from the rear. i think it got worse since i installed a UMI tunnel mount tq arm. there is a metalic clunk noise when i let the clutch a little quick. im gonna start looking into this i guess today. any recommended u-joints if it is one? im about to do a search

wrd1972

iTrader: (12)

Only use Spicer u-joints.