"Thunk" sound coming from rear end

[mazikowski]

I have a non-turbo '82 280ZX with (I believe) the R180 diff. Whenever I shift (or otherwise abruptly apply power to the rear end) I hear and feel a loud "THUNK".

From what I can tell after jacking the back end up, one of the half-shafts seems loose. With the car in gear, if I try turning it, it moves a few degrees in either direction. If I do the same thing with the other one, it does not move at all.

Does anyone know what would cause this and, more importantly, what I can do to fix it. I have already drained and replaced the gear lube in the diff.

[SteveJ]

I know the S30 FSMs have a good troubleshooting guide for the rear ends. The S130 FSM might have one, too. If you need a copy, go to http://www.xenons130.com.

Also, make sure all of the bolts are still on and tight. They can back off. Bolts are also a lot less expensive than half shafts.

[torker]

Also check the rearend isolator mount ( rubber mount on the front of the rearend) Search rearend clunk and you will find threads. Welcome to the site btw

[Zed Head]

If one half-shaft moves (rotates) with the wheels on the ground, it could be a u-joint or both (or loose splines but that is unlikely, I believe). With wheels on the ground the half-shafts should not rotate at all, they should be locked solidly on to the wheel.

It's hard to see the u-joint move with the half-shaft on the car, even with a bright light and your head twisted in to a good position. Sometimes you can stick a screwdriver in the joint and wiggle it around. Look for signs of rust at the seal also, I had a dry one on my car and you could see some rusty residue around the seal. It didn't take much movement to get an audible clank/clunk.

You can remove the half-shaft working from the wheel well of the car,with the wheel off.

Edited January 18, 2011 by Zed Head

[johntlr1000]

I had a Ujoint in my drive shaft go out one time sounded just similar to what you are describing. Problem is I could never find a ujoint to fit and from what I was told the drive shaft on the zx is non-servicable. Had to buy one from a bone yard