Truck rear wheels lock up without applying brakes

[GoneFishin]

My step father just bought a used 98 gmc. We took it for a drive and twice now the tires have locked right up skidding to a halt then eventually "brake" free.

Before this started I took it for a drive and got it up to 140 to test it and after letting off the gas it shook like crazy. Made us realize something was wrong.

Now today it had locked up twice while going 50km/h without touching the brakes.

When I first got in it today it didn't want to roll in reverse. I kept hitting the gas but it felt almost as if the truck tires were chocked. I let off the gas a couple times, played with the brakes then it was all fine. We took it for a drive and tried pumping the brakes going slow, fast, everything we could think of with no issues. We were thinking that since it was supposed to of had a new brake job and e-cable done yesterday that maybe the new pads were rubbing. We were almost home then all of a sudden the back tires locked right up and we had skid about 30 feet and came to a stop. It happened to him earlier in the day also and both times the brakes were never touched. We tried pulling over and they stayed locked then all of a sudden you could hear it "break" free.

He's going to take it back in tomorrow to get fixed and thinks it's the brakes. Could this be a problem with the drive train? If not what could cause the brakes to lock up without being applied?

[skeeter99]

My step father just bought a used 98 gmc. We took it for a drive and twice now the tires have locked right up skidding to a halt then eventually "brake" free. Before this started I took it for a drive and got it up to 140 to test it and after letting off the gas it shook like crazy. Made us realize something was wrong. Now today it had locked up twice while going 50km/h without touching the brakes. When I first got in it today it didn't want to roll in reverse. I kept hitting the gas but it felt almost as if the truck tires were chocked. I let off the gas a couple times, played with the brakes then it was all fine. We took it for a drive and tried pumping the brakes going slow, fast, everything we could think of with no issues. We were thinking that since it was supposed to of had a new brake job and e-cable done yesterday that maybe the new pads were rubbing. We were almost home then all of a sudden the back tires locked right up and we had skid about 30 feet and came to a stop. It happened to him earlier in the day also and both times the brakes were never touched. We tried pulling over and they stayed locked then all of a sudden you could hear it "break" free. He's going to take it back in tomorrow to get fixed and thinks it's the brakes. Could this be a problem with the drive train? If not what could cause the brakes to lock up without being applied?

parking brake is seized on typical with gm the 90's gm's easy fix or they overadjusted the rears and are constantly rubbing the drums which kinda sounds like what you are experiencling since it breaks free then comes back Edited February 6, 2012 by skeeter99

[bigbuck]

Did he buy it certified?? If so, drop it off at the shop that did the cert and have them fix it on their dime. Otherwise, let them know you will be notifying the MTO of the problems with the brakes.

Most likely, the problems are with brakes that are sticking, could be bad wheel cylinders, out of adjustment brake shoes, bad calipers, etc... Have it looked at pronto, it's not safe the way it is right now.

[Billy Bob]

IF this truck has rear disc brakes I would say it was a calliper hanging up and the pins would need a good cleaning and a calliper lube applied....but I believe this is a old style drum brake in the rear of this truck...RIGHT ? ? ?....so then I believe the shoes are either adjust just a bit too tight OR you have a hanging up E-Brake....either way what is happening is that the shoes are dragging a bit on the drums, then heat up the drum and shoes and start locking up because of this.....remove the drum and inspect the E-Brake for proper operation AND back off on the adjuster of the brakes (the star wheel) to give you a bit more clearance on the shoes from the drum...

 

Now the best way to see if this is happening when it does happen is once the rears brakes start to lock up....PULL OVER to the side of the road and go and feel for LOTS of heat from the rear drums....this will also happen "IF" you have disc brakes hanging up....JUST BE CAREFUL as these drums/rotors get VERY hot to the touch.

 

Remember to report back,

 

Bob

[vance]

Improper adjustment some where and another possibility combined with the adjustment is they might have put the shoes on with the leading and following shoes on backwards,that happened to me with almost almost catastrophic results when the rears locked up and sent me for a wild ride just after leaving the garage from have a brake job.

 

vance

[Kingsalmon]

I don't know, but that sounds more of a rear differential going than brakes. If you are not touching the brakes and the rears are locking up at the same time, I don't think its the brakes. Had an early 90's Jimmy that gave us the same problem. Turns out it was the rear differential bearings.

 

KingSalmon

Edited February 6, 2012 by Kingsalmon

[BillM]

Yup, I can't see the e-brake locking up a set of drums at 50mph... I've guessing you've got a rear diff issue as well.

[LesCulpJr]

Doesn't sound like brakes to me...Please don't go "taking it up to 140" anymore You could hurt/kill yourself or worse - someone else's family

[Billy Bob]

Yup, I can't see the e-brake locking up a set of drums at 50mph... I've guessing you've got a rear diff issue as well.

 

I can....as this vehicle probably has drum brakes and if it does then both rear brake shoes come in contact with the drum and can very much make this problem for the owner...this is unlike the E-brakes that come with a rear disc brakes....that's why in my first post I said to pull over and feel for extreme heat coming from the rear brakes....this is a sign that the brakes are the culprit in this mystery problem...

[BillM]

Both tires at the same time doesn't say 'brakes' to me. But hopefully the OP figures out what's going wrong before he ends up in a ditch!

[ecmilley]

sounds like the diff is pooched, those centrifugal limited slips do things like this when the clock spring goes inside

[COUNTRYBOY]

I WOULD GRAB THE DRIVE SHAFT NEAR THE U JOINT AT THE DIFF, SEE IT THERE IS ANY PLAY, ADJUSTERS IN BACKWARDS? I WOULDN'T BE TEST DRIVING IT AT 140 THOUGH UNLESS YOU LIKE EXCITEMENT