gmc rear end stuck locked

[huckelberry]

I have a 1987 gmc sierra that I bought a couple of weeks ago. I drove over a little patch of ice yesterday and the rear end locked like it is supposed to but it will not unlock back to limited slip. I serviced it today and added limited silp additive but to no avail. If I make a hard right turn it really binds and clunks. Do any of y'all know what I can do to get it unlocked or what might be stuck inside the diff.

Thanks

 

[glennwolf]

Re: gmc rear end stuck locked

Try puting it in reverse and making some turns in reverse. Is it a gm limited slip or an aftermarket?

 

[huckelberry]

Re: gmc rear end stuck locked

I think it might be stuck brakes, I'm about to go out there and see.

 

[huckelberry]

Re: gmc rear end stuck locked

Well the brakes were not stuck, or so I thought. And after finially locating a 3.42 ratio posi diff., buying it, and then getting it in. I found out that I have a bad master cylinder. The right rear brake was dragging just enough to keep the diff. locked. I made a hard right hand turn and broke the carrier in half. Of course the ring and pinion went also. Just hope my junkyard unit holds up long enough to rebuild the broke one. Oh well, just thought i'd let yall know just in case someone else runs into this they will get by with a $58.00 repair bill instead of $732.64.

 

[Stachi]

Re: gmc rear end stuck locked

Well the brakes were not stuck, or so I thought. And after finially locating a 3.42 ratio posi diff., buying it, and then getting it in. I found out that I have a bad master cylinder. The right rear brake was dragging just enough to keep the diff. locked. I made a hard right hand turn and broke the carrier in half. Of course the ring and pinion went also. Just hope my junkyard unit holds up long enough to rebuild the broke one. Oh well, just thought i'd let yall know just in case someone else runs into this they will get by with a $58.00 repair bill instead of $732.64.

hey buddy, sorry to hear about your repair bill... not to be nit picky , but it sounds like you had a sticking slave cylinder (wheel cylinder). I am an ASE certified mechanic...sounds like you have a good handle on the rest of it all...too bad ya don't live close to me...I know the best transmission/driveline mechanic for your repair....most of what he does is high performance work (drag racing)... best I have ever seen at setting up GM rearends...beyond that , he is also a GM man at heart...good luck bro !