Rear diff issues
 

Lately I've been having some issues with the rear diff in my 78. It operates normally 95% of the time but every once in a while it locks the two wheels together and doesn't allow the outside tire to turn faster around corners.

Is this a common symptom of a dying rear end? When it gets worse will it just stay locked in the no-slip mode or will it cause both rear wheels to lock up (stop spinning) while I'm cruising down the road? Without pulling the cover off, is it possible for you to be pretty sure of what needs replacing?

Re: Rear diff issues
 

Its just guessing not pulling the cover off. Its not that bad of a job to pull just smelly.

Re: Rear diff issues
 

OK, tomorrow's my day off so I'll see what I can see.

Re: Rear diff issues
 

Change the oil and also put the GM limited slip additive in it. Do a few tight circles in each direction to work it in. (Assumming the inspection doesn't look bad)

Re: Rear diff issues
 

Sounds like a GovLoc rear instead of a clutch type posi . I would say change the fluid but also make sure the tires are the same size and properly inflated . That can cause it to lock up and if there is a different diameter tire issue , it wont unlock correctly . Frank

Re: Rear diff issues
 

Thanks guys. I keep a close eye on tire pressures and they are all the same size. It's the stock open rear diff so will that GM limited slip additive still help?

Re: Rear diff issues
 

If your sure it's an open carrrier, the additive will do nothing really. If indeed you have an open carrier about the only answer then is... FOD (Foreign Object Debris) floating around inside getting between the moving parts locking things up. This happened to a buddy of mine in his '55 Belair back in 76, wasn't pretty at all. He was doing between 20 & 30 when it completely locked up. Pretty scary ride for about 30 seconds untill all motion ceased.
Wish you the best & be very careful driving, I would get it fixed asap.

Terry:)

Re: Rear diff issues
 

Actually that's exactly what my buddy said would happen and why I started the thread. Sounds like a shocking experience.

I pulled the cover off today but unfortunately my camera died when I tried to take the first picture of the internals. I inspected it pretty carefully but couldn't find any blatant problems. I was told to expect small metal shavings kind of like the fine stuff left behind by an eraser and I did but I also found 8 larger pieces.

Do you think those are big enough to have been the ones that were causing the problem? I took it around the block and everything was fine so far.

http://img98.imageshack.us/img98/6636/p1010003hl2.jpg

Re: Rear diff issues
 

That is NOT good.

Re: Rear diff issues
 

looks like you got some tooth missing on the ring gear

Re: Rear diff issues
 

Everything in the rear diff is necessary and the metal pictured came from somewhere . No matter where that was , it aint good . Frank

Re: Rear diff issues
 

I'm thinking it may be the spider gears starting to go. It would have been nice to get a picture of the inside. They sell a kit to replace those. I believe it comes with the spider gears, bearings, shaft and bolt.

Re: Rear diff issues
 

I was thinking about upgrading to a posi. Would doing that replace my currently broken parts, or would that be something different entirely?

Re: Rear diff issues
 

As long as you ring gear and pinion are ok, the limited slip will fix the problem. If there are pieces missing from them I HIGHLY recommend fixing them also.

It looks like spider gears to me also.

Re: Rear diff issues
 

It was fine until tonight. It locked the two wheels together again. I guess I'll have to look into upgrades.

I'm considering the Moser eaton posi unit, unless somebody has a reason to avoid them.

Re: Rear diff issues
 

Do I need a 30 spline unit???