Rear brakes locking up - The 1947 - Present Chevrolet & GMC Truck Message Board Network

Pro69 · 01-29-2008, 05:03 AM

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.

Longhorn Man · 01-29-2008, 05:30 AM

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!

Sweet72 · 01-29-2008, 05:34 AM

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

Pro69 · 01-29-2008, 05:56 AM

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.

Longhorn Man · 01-29-2008, 06:15 AM

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

Pro69 · 01-29-2008, 06:21 AM

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

cdowns · 01-29-2008, 09:56 AM

Quote:

Originally Posted by Pro69

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

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//

**Palf70Step** · 01-29-2008, 07:51 AM

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.

Eichorst69 · 01-29-2008, 09:21 AM

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

Painter D · 01-29-2008, 09:31 AM

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

**truckdude239** · 01-29-2008, 10:05 AM

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

tim21391 · 01-29-2008, 10:58 AM

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

soba_03 · 01-29-2008, 11:17 AM

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.

Pro69 · 02-01-2008, 11:35 AM

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.

wibilly · 02-01-2008, 01:59 PM

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

01-29-2008, 05:03 AM	#1
Pro69 Registered User Join Date: Nov 2006 Location: Chula Vista Ca. Posts: 4	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.

01-29-2008, 05:30 AM	#2
Longhorn Man its all about the +6 inches Join Date: Jan 2001 Location: Hilliard Ohio Posts: 2,693	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! Last edited by Longhorn Man; 01-29-2008 at 05:31 AM.

01-29-2008, 05:34 AM	#3
Sweet72 Registered User Join Date: Nov 2003 Location: Alexandria, VA Posts: 1,534	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 __________________ '72 GMC SWB C1500 Custom, frame-off in progress. 383 SBC, 9:1CR, Comp Cams XE262H, Scat internal balanced crank, Eagle SIR 6" rods, Keith Black dish pistons, Dart Iron Eagle 72/180 heads, Weiand Stealth intake, Stewart stage I water pump, Holley 4bbl vac sec, TH350 with B&M Shift Improver Kit. 12 bolt positraction.

01-29-2008, 05:56 AM	#4
Pro69 Registered User Join Date: Nov 2006 Location: Chula Vista Ca. Posts: 4	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.

01-29-2008, 06:15 AM	#5
Longhorn Man its all about the +6 inches Join Date: Jan 2001 Location: Hilliard Ohio Posts: 2,693	Re: Rear brakes locking up I wonder if you got the leading shoe and trailing shoe swapped around.

01-29-2008, 06:21 AM	#6
Pro69 Registered User Join Date: Nov 2006 Location: Chula Vista Ca. Posts: 4	Re: Rear brakes locking up Dont they only go on one way? If not that may be something I can check.

01-29-2008, 07:51 AM	#8
Palf70Step State of Confusion! Join Date: Jul 2002 Location: Gulfport, MS USA Posts: 47,083	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. __________________ Bill 1970 Chevy Custom/10 LWB Fleetside 2010 Toyota Tacoma PreRunner SR5 Double Cab - DD Member of Louisiana Classic Truck Club (LCTC) Bill's Gallery Life isn't tied with a bow, but it's still a gift. Live simply. Love generously. Care deeply. Speak kindly. Leave the rest to God!

01-29-2008, 09:21 AM	#9
Eichorst69 Registered User Join Date: Jan 2007 Location: South Florida Posts: 158	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

01-29-2008, 09:31 AM	#10
Painter D Registered User Join Date: Jun 2007 Location: DFW (Forney) Posts: 1,529	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

01-29-2008, 10:05 AM	#11
truckdude239 Senior Member Join Date: Sep 2005 Location: Lewisville, Nc Posts: 10,237	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 __________________ David fuller Ase Certified Mechanic Click here to help support our board!! 1971 Chevy c-10 under going a 4.8l LSx swap Build Thread http://67-72chevytrucks.com/vboard/s...d.php?t=421305 2007 Honda Accord my daily 145kmiles 2002 Honda Accord 4 door With 330k(sisters car) 2005 toyota Avalon 228k( brothers car) 2002 Sububran 5.3 245k 2000 Tahoe 5.3l 378 General manager for Marco's Carwash & lube

01-29-2008, 10:58 AM	#12
tim21391 Registered User Join Date: Jul 2007 Location: Salina, Kansas Posts: 1,998	Re: Rear brakes locking up could it be bad wheel cylinders or did he say those were new too..im just throwing ideas out

01-29-2008, 11:17 AM	#13
soba_03 Registered User Join Date: Sep 2007 Location: Fairdale, Kentucky Posts: 561	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.

02-01-2008, 11:35 AM	#14
Pro69 Registered User Join Date: Nov 2006 Location: Chula Vista Ca. Posts: 4	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.

02-01-2008, 01:59 PM	#15
wibilly Senior Member Join Date: Nov 2005 Location: northwestern wi Posts: 2,111	Re: Rear brakes locking up i think your rear brakes are not adusted tight enough causing them to shift when applied . __________________ common sense isn't so common anymore



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