Rear end thud

[melv1n]

Got a frustrating problem with my z20 and hoped some experience from you guys could help to diagnose it.
There is a loud thumping generating from the rear end. It gets faster as the car speeds up. It present all the time UNLESS i turn right where the noise disappears entirely.
The right rear drive shaft appears not to be rotating true within the inboard joint, so i pulled it out and removed the boot and the bearings seem fine with no play in them and move around in all directions freely. The tsrm says not to disassemble the outboard join so iv'e left that alone but again it seems to have fine movement with no strange noises.

The noise is gone entirely with the drive shafts removed so i doubt it's the diff or drive shaft from the gearbox.
What really stumps me is it disappearing entirely on right hand corners.
Iv'e read a few threads where wheel bearings caused similar symptoms.

Excuse the noobness of this, im really trying to have a crack at doing as much on this car as i can myself and i enjoy it and im learning.
My best guess is the bearings in one of the joints is binding up but wtf do i know.
So what do you guys think of these symptoms?
Whats the best way to test wheel bearing without removing them?

Cheers for ya time guys.

[thechuckster]

try/loan another shaft - that would at confirm it's not one of the uni joints in the shaft.

[CELICASUPRA7M]

tried swapping rear wheels to front, front wheels to rear? could be a tyre bulge.

If not maybe sounds like a wheel bearing problem, a mate's soarer had similar prob in front end, turn one way noise got really bad ( thump thump thump) turn the other way and it vanished. remember when your turning to the right, the right shaft and wheel bearings slow down a little bit.
good luck

[melv1n]

Cheers man, the problem there is it's a 1989.5 z20 so the rear end is all jza70 spec. Much less common. I actually have a z20 parts car not realising how great the difference underneath. I will ring around though.
And it does it with the wheels off so nothing so simple unfortunately.

Anyone else experianced anything like this?

Cheers for the advice guys

[LeeRoy]

Could also be the wheel weights hitting on the strut. Had your tyres changed recently?

[melv1n]

I had actually chucked on a set of stock wheels on not long before it started.
While i cant drive it without wheels it's definitely making noises up on stands with no wheels on.
It's a suggestion id love to be right though. And one i will 100% eliminate in the morning.

I pulled the brakes off today so i could make sure the wheel bearings are good. Holding the wheel studs there is a very small amount of play but its the same on both sides and the bearings are just about silent while spinning.

[RobertoX]

Swap in a new drive shafts and see if it goes away, it sounds like a uni joint problem.
Can you swap them side to side? (ie are they the same left to right)
Then see if the noise happens and then goes away when you turn left.

[melv1n]

I should be able to reverse them. I'll do that tomorrow. Im also chasing down another shaft and may have found one.
The inboard joint on these is rebuildable but as the tsrm says not to dissmantle the outboard joint im assuming it isnt. I cant find any drive shaft specialists around here so i might try one of the local 4x4 specialists.

Thanks guys.

[melv1n]

So i got a chance to play with this today, it's doing it with no wheels on so its not the wheels. Pulled the brakes off and it still does it. Swapped the drive shafts over and it stopped.
Both wheels where spinning and all was quite. The left wheel stopped spinning and thump thump thump she went. So i encouraged the left wheel to spin with my foot and the noise stop'd.

That to me says the diff is fucked. And would explain why the noise goes on right hand corners, when the left wheel is spinning faster.

Anyone disagree with this?

[melv1n]

Thoughts anyone?
I dont want to pick up a new diff till im 100%.