Rear brakes locking up
 

Hello everyone this the first time I've posted something so here it goes.
I have a 69 SWB with a 350/700r4 combo. I recently installed a 5 lug rear out a 71 chevy and the rear brakes lock up even after bleeding them several times. The front has disc brakes and a new prop. valve, master cylinder and brake booster. I installed all new parts on the rear axle prior to installing it so I dont think it has anything to do with that. I also read on this forum about the rear brake line not being any good and that causing them to lockup. Mine is in good shape also the rear e-brake is not connected. So i'm kinda running out of options. Any help would be greatly appreicated. Tks.

Re: Rear brakes locking up
 

Since it is all new in there, I'll assume you don't have any oil or brake fluid soaked into the brake shoe lining. May wanna double check that to be sure if there is any question about it.
If it is all clean, then try adjusting the shoes up.If they are backed off too much they can do this due to the self energizing aspect designed into drum brakes.

Oh, and welcome to the board.... 14 months later!

Re: Rear brakes locking up
 

Sounds like the proportioning valve isn't setup properly. Here's a article that might be helpful.
http://www.chevyhiperformance.com/te...lve/index.html

Re: Rear brakes locking up
 

Thanks guys I'll double check that stuff and check the setup on the prop. valve. I'm not to sure how to adjust the rear drums so I think I got an old Chiltons around I can maybe check in. I'll let you know what I come up with.

Re: Rear brakes locking up
 

I wonder if you got the leading shoe and trailing shoe swapped around.

Re: Rear brakes locking up
 

Dont they only go on one way? If not that may be something I can check.

Re: Rear brakes locking up
 

You didn't mention this part specifically, so I am asking. How about the rubber line that feeds the rear axle. If it is very old, it could very well be letting the fluid go to the rear wheels, but not letting it flow back smoothly when the braking is finished. The one on my daughter's 82 did this. Bout drove me nuts till I replaced it.

Re: Rear brakes locking up
 

Are the front brakes working properly???
Try bleeding the front wheels and the master. Maybe the rear are working properly and the front are not working at all.

Rob

Re: Rear brakes locking up
 

i have the exact same setup as you do. same motor, trans, brakes setup etc.. i also had this same problem with mine. so heres my first question ,you said you had a new proportioning valve, is it an adjustable, or the factory style. by , (factory) i mean a disc front ,drum rear valve. i replaced the factory style first and it did nothing , however i put the adjustable one on and it fixed it. i also had a new master cylinder and it turned out to be bad i had to get another one. hope this helps

Re: Rear brakes locking up
 

easy to mixup if not paying attention//a pair of brake shoes has one brake with a longer lining than the other// the brake shoe with the smaller brake lining goes at the front the brake shoe with the longer brake lining to the rear//

Re: Rear brakes locking up
 

can you take a picture of the rear brake linings witht he drum off and we can tell you if the shoes are backwards and yes you can install them backwards

Re: Rear brakes locking up
 

could it be bad wheel cylinders or did he say those were new too..im just throwing ideas out

Re: Rear brakes locking up
 

You said that you installed disc's in the rear, I assume that you did this after you had the front brakes and master cylinder. I would say that very likely could be proportioning vale. if it's for disc and drum.

Re: Rear brakes locking up
 

Gents, thanks for all the info I checked the rubber brake line that leads to the rear axle and it's in good shape. As I mentioned before all the rear drum stuff is new hardware,drums,shoes and wheel cylinders. The prop. valve I got is new from CCP, the prop is set up for disc front and drum rear. Do you guys think the master could be bad? I think someone asked if the front brakes were working fine and they are. I'm gonna pull the drums off and double check some things. Thanks.

Re: Rear brakes locking up
 

i think your rear brakes are not adusted tight enough causing them to shift when applied .