Locking rear wheels

radrado · January 11, 2002

On my way to work today I had the following twice. In a slow left turn it felt like both my rear wheels locked. One of the times this happened I was pulling into a parking lot and I stopped. When I hit the gas the wheels where still locked. When the wheels locked I didn't hear the differential lock. Did this happen to anyone? Any idea what is happening?

Suburbanite · January 12, 2002

I don't whether this is the same problem but I was told by the salesman that sold me my new-used truck that he experienced rear tire lockup while out on a test-drive of the vehicle before I picked it up. Problem turned out to be the rear brakes locking. He said the mechanics at the local shop where he took it in for repair said "something" was sticking causing the brakes to be applied. Seems to have been fixed because I haven't had a problem & it's been about 4 months.

kengsxr · January 12, 2002

could be the rt rr caliper sticking...seen a few come through our shop

radrado · January 12, 2002

Thanx for the input. So what's the fix if it is the caliper sticking?

Suburbanite · January 13, 2002

Thanx for the input. So what's the fix if it is the caliper sticking?

Cleaning?

Tho it seems kinda strange that such a new vehicle would already be experiencing that sort of problem. Mine is a '95 K3500. I have read that it's a good idea to thoroughly pressure clean the drum area after off-roading in the wet stuff. Seems 'gunk' gets in the drums & drys causing the rear brakes to lock. Just remembered that newer trucks were availble with rear disc brakes so don't even know whether info would apply to your truck.

Suburbanite · January 13, 2002

Just came across another possibility at the www.gm-diesel.com website. It's a response to someone complaining about their ABS acting up. Here it is:

trucktech

Just Joined

Member # 827

Rate Member

posted 01-12-2002 17:36

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you have a malfunctioning wheel speed sensor thats telling ebcm that there is a lockup.You need a scan tool to find which one is acting up,, and the light will not come on, because it doesnt know there's a problem.

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Posts: 2 | From: Long Island NY | Registered: Jan 2002 | IP: Logged

Shaners · January 13, 2002

I had mine do that once, but I think it was because I spun my tires a little on the previous turn. I think it takes a few hundred feet for the "locker" to unlock.

Here is my scenerio: Easy right turn from a stop sign... lit the tires up!!! 100 feet or so later a 90 degree turn to the left... rear end felt "bound up" and just rolled through the turn. 150 feet later 90 degree turn to the right, and all was OK again!!!

These rear ends have a locker in them, and I don't know how long they actually stay locked... It took mine a ways to unlock... BTW, the big old crewcab of mine had to look good sliding sideways under throttle!!!

radrado · January 14, 2002

When the lockup happened the first thing I thought was that the locking differential playing a joke on me. After Suburbanite and kengsxr suggested it could be the brakes I gave them a close inspection and everything looked fine. (BTW the brakes are discs) About the thread on gm-diesel.com, if the ABS senses a lockup shouldn't it release brake pressure? In my case the wheels locked so it can't be that. So I'm back to square one. The Chevy dealer here $ðx and I'm afraid of taking the truck to them.

Here is my scenerio: Easy right turn from a stop sign... lit the tires up!!! 100 feet or so later a 90 degree turn to the left... rear end felt "bound up" and just rolled through the turn. 150 feet later 90 degree turn to the right, and all was OK again!!!

Shaners, when your rear was "bound up" did you skid or were the wheels still rolling?

BTW When the G80 senses a difference in wheel speed, flyweights will move to lock the axle. When the speed differential is gone the flyweights will move back to a position where the axle will unlock. This all is supposed to happen pretty fast.

The wheels have not locked again on me, but I'm thinking of giving the axle an inspection to see if everything in there is the way it should be.

Sorry fo the long post fellas! If any of you think of something new it would be appreciated!

Shaners · January 14, 2002

radrado,

What I felt (and heard) was definatly the rear wheels still "locked" through the differential. It felt like when you turn on dry roads with 4x4 engaged but not as severe.

I actually heard about 3 chirps from the inside rear tire as it was being forced to spin at the same speed as the other rear tire.

After I went around the corner the rearend unlocked and all was OK.

Z71GUY · January 14, 2002

Shaners,

My truck acts exactly as yours did. If I spin out, my rear end seems to stay locked for about 2 city blocks (rough idea of distance needed to unlock). Sometimes it will unlock with less distance, but 90% of the time its locked for a bit....

Eric

radrado · January 15, 2002

Shaners,

Thanks for the info. Till now every time my axle locked it unlocked right away when normal traction was restored. Right now I think that I'll wait to see if the truck does this again and if it does maybe I'll have a better idea of what to do with it.

raventai · January 15, 2002

your rear disks have a drum parking brake inside the "hat"

that is a manual sys so there is not much to go wrong I guess it could get some junk in there

radrado · January 26, 2002

It did it again! I just got back from a week of vacation. When I was on my way to the airport a week ago the rear locked up again. This time it did not take me by surprise so I payed attention. I'm sure it is the differential. I'm going to check it next week.