Rear brakes locking up

[revyurengine]

1990 vehicle... The other day when it was raining I tried to leave work. I rolled ahead about 5 feet then bang,the rear wheel locked up. I could move back but not ahead. I removed both drums and there was a lot of brake dust. Tried again, got about 10 feet , bang the left wheel locked up. (i could see the mark on the road) This time I coudn't back up. I tapped on the inside backing plate , then it released. Went ahead another 10 feet , bang, the right rear wheel locked up.Banged on the inside at the backing plate, you can see it release and roll ahead a little.I had removed the parking brake cable a few months ago as it was seized and haven't replaced it yet, so could that affect it?
Once I drove for a few miles it didn't happen again so far.
I wasn't touching the brakes when this happened. How can it happen??

Thanks

[j cAT]

Originally Posted by revyurengine

1990 vehicle... The other day when it was raining I tried to leave work. I rolled ahead about 5 feet then bang,the rear wheel locked up. I could move back but not ahead. I removed both drums and there was a lot of brake dust. Tried again, got about 10 feet , bang the left wheel locked up. (i could see the mark on the road) This time I coudn't back up. I tapped on the inside backing plate , then it released. Went ahead another 10 feet , bang, the right rear wheel locked up.Banged on the inside at the backing plate, you can see it release and roll ahead a little.I had removed the parking brake cable a few months ago as it was seized and haven't replaced it yet, so could that affect it?
Once I drove for a few miles it didn't happen again so far.
I wasn't touching the brakes when this happened. How can it happen??

Thanks

so what condition are the springs . if rusted replace. If the drums are old replace them. could be they are excessively worn .

[revyurengine]

I looked at the springs and they seemed Ok but the small ones on the bottom didn't have any tension. I replaced the shoes and all the springs , so far so good.(one day) The drums are original and look OK.
Can someone explain how this could be happening. How can the brake shoe kink itself so tight ,it locks up the wheel??
Is it possible the rear end could be the culprit here also? There is alot of play there.

Thanks

[j cAT]

Originally Posted by revyurengine

I looked at the springs and they seemed Ok but the small ones on the bottom didn't have any tension. I replaced the shoes and all the springs , so far so good.(one day) The drums are original and look OK.
Can someone explain how this could be happening. How can the brake shoe kink itself so tight ,it locks up the wheel??
Is it possible the rear end could be the culprit here also? There is alot of play there.

Thanks

the drums if old replace. when worn this can cause problems with the shoes ..the shoes replaced ,,,,,,,if only worn at the top this means the drum is too big / worn !

oil on shoes can cause shoes to lock up.

the rear diff could be causing this but would not be so intermittent..

rusty springs are bad springs...................

brake shoes are no longer made out of asbestos. this means the drums wear at a rapid amount..MAYBE TWO SHOE REPLACEMENTS,,,,.............

[revyurengine]

Thanks for the info!

[kahjdh]

Nobody said wheel cyclinders or parking brake cables. Make sure all cables are free and the wheel cyclinders are not siezed up or leaking.

[danielsatur]

It's probably time to flush the brake system too!

[jdmccright]

Sounds like the retracting spring that is hooked next to the brake adjusting assembly is weak, broke, or missing. Without this, the brake shoes can swing freely against the shoe and then cause it to jam.

Another possibility is that you have the G80 locking diff and the springs that control the little weights have broken, causing them to engage with little to no rolling....were you turning when the rear locked up? These won't spin unless there is a difference in left/right wheel speeds.

[Kevcules]

Thanks for the replies guys...

The springs were all in good shape except the bottom one holding the shoes together on the stop portion of the backing plate. I decided to change all the springs along with new shoes. The shoes were still in good shape but they seemed glazed and had some cracking through them. I didn't see anything broken or missing which is what I expected to see.
The wheel cylinders weren't leaking and the pistons moved freely from side to side.
The parking brake cables are a popular answer but i had removed the main park cable (coming from the park brake pedal) 6-8 months ago because it was seized and haven't replaced it. I even completely removed the cable assembly from the drivers side backing plate so i had nothing inside the drum as far as a parking brake cable. The other side still has the cable assembly attached to the backing plate,but nothing to pull on it. I have since removed everything on the passenger side too.
I thought it was definitely my differential because the wheels lock up without me touching the brakes while I was rolling. But since I can tap on the backing plates when it happens and I can see a physical kinking ahead as the wheel frees up , I'm leaning towards brakes again. I know little about differentials but it would seem to me that if it decided to seize up it wouldn't free up so easily?
I had to replace a brake line a few years ago so the fluid is fairly fresh.
Since the new shoes and springs , all is well so far for 3 days . Haven't had another damp day yet which is when it seems to happen.

Thanks a lot for the comments !

[j cAT]

Originally Posted by Kevcules

Thanks for the replies guys...

The springs were all in good shape except the bottom one holding the shoes together on the stop portion of the backing plate. I decided to change all the springs along with new shoes. The shoes were still in good shape but they seemed glazed and had some cracking through them. I didn't see anything broken or missing which is what I expected to see.
The wheel cylinders weren't leaking and the pistons moved freely from side to side.
The parking brake cables are a popular answer but i had removed the main park cable (coming from the park brake pedal) 6-8 months ago because it was seized and haven't replaced it. I even completely removed the cable assembly from the drivers side backing plate so i had nothing inside the drum as far as a parking brake cable. The other side still has the cable assembly attached to the backing plate,but nothing to pull on it. I have since removed everything on the passenger side too.
I thought it was definitely my differential because the wheels lock up without me touching the brakes while I was rolling. But since I can tap on the backing plates when it happens and I can see a physical kinking ahead as the wheel frees up , I'm leaning towards brakes again. I know little about differentials but it would seem to me that if it decided to seize up it wouldn't free up so easily?
I had to replace a brake line a few years ago so the fluid is fairly fresh.
Since the new shoes and springs , all is well so far for 3 days . Haven't had another damp day yet which is when it seems to happen.

Thanks a lot for the comments !

this description is well written. you had heat cracks on the old shoes so that means the brakes caused your lockup issue..

when this occurs [heat cracks] the drum must be replaced. they become bell shaped and will not work correctly.

this may work until the shoes get 50% worn then lock up again , if you do not get new drums.

[revyurengine]

Originally Posted by j cAT

this description is well written. you had heat cracks on the old shoes so that means the brakes caused your lockup issue..

when this occurs [heat cracks] the drum must be replaced. they become bell shaped and will not work correctly.

this may work until the shoes get 50% worn then lock up again , if you do not get new drums.

I totally agree with you J Cat , I'll definitely get a new set of drums asap... Thanks