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Rear end locking up?

M

Mad Max

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I got a 88 GMC 1500 SLX Short box and the rear axel has started locking up on me.
I just got the thing not to long ago because I didn't want to use my 88 Suburban for a work truck.
Is it posible that a posi can lock down the rear.
It hapend once goin over some tracks and all I did was put it in 4 low and did a bit of reverse and foward and she broke loose.
I thought there was some crap in the drums so I cleaned them out.
Last monday we had a kickass snow storm and I had to run into town for some beer and had it into 4 high and when I went around a tight bend it did it again. WTF?
Has anybody had this happen to them before?
I left the truck at home and had to take the Burb to work here in Niagara and got it all coverd in salt crap.
This Saturday I'm gonna get on this thing startin from the rear so if anyone's got some info to pass on it would be a great help.
Thanks Max.
 
Ya they were a bit gooie but I didn't see no seal leakage.
That was the first thing I checked.
Ya never know maybe there's no fluid left to leak?
 
maybe theres a broken tooth on a gear that occasionally gets caught? have you opened up the rearend yet? Could it be that 2 gears have problems and every so many revolutions, they meet and lockup?
 
If they were gooey, that points to gear oil leakage. You should plan on replacing the rear shoes ASAP. And, yeah, double check the fluid level in that diff before you drive it again. While you're at it, take the time to check ALL of the fluids in the truck.

Your problem could very well be a combination of low gear oil in the diff and sticky brake shoes.

BTW, welcome to CK5!!! :thumb:
 
Ya come Saturday morn that cover's comin off for thourough inspection.
I gave them shoes a good varsol bath and drums as well. then wiped it all clean.
The thing I find that is a bit odd is the last time it locked up on mon. the roads were all coverd in ice and snow and I had to drag the truck a good 100' or so in 4 high before it broke loose.
I guess there's clutches in the transfer case cause if was a direct conection it woulnd allow the front to drive while the back is locked up I guess.
 
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Is it the brakes locking up, or the whole differntial? One side or both? If you have to go forward, backward, or drag it 100' it sounds like a mechanical failure in the rear diff. pop the cover, and check things out. rotate the ring gear, and check the pinion gear. Is it a "locking differential" or open?
 
Nobody else commented about gear fragments or other litir being swirled around in the differential and being caught in the gears? maybe he has fulltime 4wd, for the front working and the rear not? But its an 88..i didnt know the tcase could differentiate in these later models.

Might as well learn on somebody elses thread..lol
 
Mad Max said:
I guess there's clutches in the transfer case cause if was a direct conection it woulnd allow the front to drive while the back is locked up I guess.
Click to expand...

Nope...no clutches. The t-case is chain driven so its a direct connection.
-Harrison
 
Cleaning the surface of the pads will do no good if the shoes are soaked in gear oil or brake fluid. The heat they generate will bring it out again.
 
What I want to know is if in 4 high, you can drive 100' with the rear end locked up, whats not connected correctly? is the rear drive shaft spinning? I got odds on a very trashed rear diff. Mangled spider gears, bits and pieces everywhere inside.
 
I just Got home and it's 2 am, been gone all week.
If I can get some sleep tonight I'm gonna get on it first thing.

Ya the road was covered in ice and snow and I was in 4 high at the time when it locked up again as I was goin up a slight grade after a corner.
Both back wheels were dragin in the snow.
Thats when I did the reverse foward thing again and bareley got to the top.
Still locked up in the back I dumped it in to 4 low and it finally broke loose.
The truck is a 5 speed std. and after all that action you can smell the clutch was doin a bit of smokin.
After that it was back to normal no funny noises or any signs of any trouble?
drove home fine.
Well I will post tomorow to let you guys know what my findings are and I hope it's a cheap fix.
 
My guess is that you've got a gov-lock, and what you are feeling/hearing is the tires scrubbing as you exit the turns. There is no way both rear tires can be solidly locked up yet the front still turns.

Only two setups I can think of that would allow what you describe (NP203 t-case or AWD) and your truck has neither.

My 14SF gov-lock was doing this, took it out today for first time in over a year, and the problem was gone. Go figure.
 
A friend of mine's was locking up on his 93, he said it was the traction unit. He's going super duty axles so he is not worried about it.
 
Well guy's it looks to be a cheap fix.
It looks like the brakes were the culprit.
It took a week before I could get back to it and as I mentioned yesterday we opend everything up and the diff pot was clean oil lookin good ect.
With one wheel in the air either side things roated smoothly
(thank god) after I backed off the brake shoes.
No brake of axel leakage to be found.
After we got her back together I took it for a spin did some hard turns put on a smoke show infront of the house and it seems to be behaving.
I'm gonna take it for a tour today.
I just wanna say thanks to all who responded with all their exellent advice and if it wasn't for this problem I wold of never found this kick-ass web site.
I have been a Chevy backyard mech. for years and even though I've owned 100's of cars 4X4's and fuel injection is still rather uncoved teretory so were still learnin over here.
 
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