105 series Diff/Prop/rear axle fault

jamieandthemagi · #1 (**permalink**) 01-21-2004, 02:52 AM

During the summer before I took the spider off the road, it had a really noisy fault. Which I need help in trying to identify.

It only occured when the car was warmed up.

when pulling away in 1st, 2nd or Reverse, there would be a loud knocking / rattling noise from the rear of the car. This would only happen if the car was not pulling away dead straight - ie. if I kept the car in a dead straight line, it would not do this.

Last night I had a quick look under the car. The intermidiate bearing looks OK & has no excessive play in it, neither do the joints in the prop. But when I grab hold of the prop, I can turn it 1/4 of a turn either way, which results in a "clonk" at the end of each turn.

I need to get this sorted before April, when I plan to have it back on the road. HELP.

**papajam** · #2 (**permalink**) 01-22-2004, 06:00 AM

With the propshaft having that much freeplay, I'd say that something in the diff has given up. I think about 1/4" - 1/2" freeplay is about the max. Is the pinion flange nut tight?

Keven · #3 (**permalink**) 01-22-2004, 07:27 AM

Are you sure your U-joints are not worn? Also is the donut ok?
I would tend to replace these items first, because they are realitvely easy and cheap, compared to tearing down the diff.

Im in the middle of a diff rebuild, and there really isnt much that can go out besides bearings. If one of the pinion brearings goes, I guess it could affect the backlash to the diff gear, and give you exess play? Other than that I cant think of anything else in there that could cause that.

**alberbat** · #4 (**permalink**) 01-24-2004, 08:56 AM

Well at the risk of being an idiot, how do you measure slack in the prop? I guess I mean where? I'm only thinking about the diameter. My prop has a thunk in it but I'm trying to ignore it after all the other things I've been doing.

Bill

gotglasses · #5 (**permalink**) 01-25-2004, 07:09 PM

When you make a turn your differential is working - yours isn't.
Jack up car on one side and turn the rear wheel , there should be smooth resistance to turning, assuming you have a limited slip diff. If you have an open rear, no posi , the wheel should turn very smoothly. If it's rough and jumpy you differential gears are shot and you need a new rear end. The little broken gear pieces will make a mess of everything else in there. A visit to your local recycler will have it right cheap enough.