locked up 80 GMC 6 auto - The 1947 - Present Chevrolet & GMC Truck Message Board Network

marvxyz1 · 12-30-2006, 07:32 PM

I replaced my gas gauge a couple of weeks ago, and went to take my 80 GMC for a ride. Truck wouldn't budge. Ended up replacing two rear wheel cylinders and disconnected the right emergency brake. The right emergency brake was dragging.. I also noticed that my old wheel cylinders were full of rust inside. Went to move the truck and it still wouldn't budge. In then put the rear wheels up in the air on jack stands, and started er up. The wheels turned freely in both forward and reverse gears. but when I lowered the truck to the ground, something is holding the truck from moving. What the heck is going on??
Could my front wheels be locked up also?? Any input you have on this would be appreciated Thanks marvxyz

**Palf70Step** · 12-30-2006, 08:50 PM

What about your front brakes?

My old 82 had a bad proportioning valve which kept the front disked locked up. It could also be the rubber lines to your calipers. Since your rear spins freely I would check the front or the proportioning valve.

marvxyz1 · 12-30-2006, 08:58 PM

If I open the bleeder valves on the front calipers would it release the brake pads from the rotors,if the proportioning valve or rubber hoses are at fault????

**Palf70Step** · 12-30-2006, 11:35 PM

Yes, I am pretty sure it does, but just temporarily.

marvxyz1 · 12-31-2006, 05:10 PM

Could the calipers be rusted up, since the rear brake cylinders were very rusted up? " I guess I've probably answered my own question."

marvxyz1 · 12-31-2006, 05:13 PM

I guess it probably makes the case for a person not to use contaminated brake fluid.

**Palf70Step** · 01-01-2007, 08:55 AM

I would flush the system of all fluid, replace the rubber lines, inspect the calipers. Refill and bleed the system then see how things work. Your rears could be rusty, but not be bad at the front. Yours is acting just like my 82 did with the proportioning valve, which was the first time I ever heard of one going bad.

marvxyz1 · 01-02-2007, 10:17 AM

Thanks for the info palf70step I'll follow your advice marvxyz

marvxyz1 · 01-02-2007, 02:57 PM

palf70styep, Just one other question --Is the proportioning valve mounted right below the radiator an have 2 brake lines coming dfrom Master cylinder &2 lines going to the front calipers attached to it??

**Palf70Step** · 01-02-2007, 03:51 PM

That's where mine was too. Practice your bad words...You'll probably need them.

marvxyz1 · 01-02-2007, 03:52 PM

Why is that?? I doesn't look to intimidating.

Russell · 01-03-2007, 01:32 AM

Getting the thing off isn't the problem, its getting the brake lines back on that can be rather frusterating, lol

I did mine when I had nothing but a rolling chassis, and I spent a few hours on that thing. Gotta make sure you don't cross-thread it, I ruined a perfectly good prop valve doing just that...

marvxyz1 · 01-03-2007, 06:23 PM

I removed ny prop valve. and on a scale of 1-10 It was a 7 or 8 . I need to get a new prop valve. Checked with the chevy dealer and they want 169.00. Definately to much. e-bay has some but I don't know if I can use them in my 80 GMC.

Example

marvxyz1 · 01-03-2007, 06:25 PM

I got it off and On a difficulty rating of one to ten I think it was a 7 or 8. Definately not easy. Not my next project will be finding a prop valve. I checked with the Chevy dealer , and they want 169.00. I told them it was to much. I'll have to find it elsewhere. I saw some on e-bay, but I don't know if I would have trouble with installing them, and if they will work.

Example=

12-30-2006, 07:32 PM	#1
marvxyz1 Registered User Join Date: Oct 2005 Location: Pittsburgh, Pa Posts: 106	locked up 80 GMC 6 auto I replaced my gas gauge a couple of weeks ago, and went to take my 80 GMC for a ride. Truck wouldn't budge. Ended up replacing two rear wheel cylinders and disconnected the right emergency brake. The right emergency brake was dragging.. I also noticed that my old wheel cylinders were full of rust inside. Went to move the truck and it still wouldn't budge. In then put the rear wheels up in the air on jack stands, and started er up. The wheels turned freely in both forward and reverse gears. but when I lowered the truck to the ground, something is holding the truck from moving. What the heck is going on?? Could my front wheels be locked up also?? Any input you have on this would be appreciated Thanks marvxyz

12-30-2006, 08:50 PM	#2
Palf70Step State of Confusion! Join Date: Jul 2002 Location: Gulfport, MS USA Posts: 47,216	Re: locked up 80 GMC 6 auto What about your front brakes? My old 82 had a bad proportioning valve which kept the front disked locked up. It could also be the rubber lines to your calipers. Since your rear spins freely I would check the front or the proportioning valve. __________________ 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!

12-30-2006, 08:58 PM	#3
marvxyz1 Registered User Join Date: Oct 2005 Location: Pittsburgh, Pa Posts: 106	Re: locked up 80 GMC 6 auto If I open the bleeder valves on the front calipers would it release the brake pads from the rotors,if the proportioning valve or rubber hoses are at fault????

12-30-2006, 11:35 PM	#4
Palf70Step State of Confusion! Join Date: Jul 2002 Location: Gulfport, MS USA Posts: 47,216	Re: locked up 80 GMC 6 auto Yes, I am pretty sure it does, but just temporarily. __________________ 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!

12-31-2006, 05:10 PM	#5
marvxyz1 Registered User Join Date: Oct 2005 Location: Pittsburgh, Pa Posts: 106	Re: locked up 80 GMC 6 auto Could the calipers be rusted up, since the rear brake cylinders were very rusted up? " I guess I've probably answered my own question."

12-31-2006, 05:13 PM	#6
marvxyz1 Registered User Join Date: Oct 2005 Location: Pittsburgh, Pa Posts: 106	Re: locked up 80 GMC 6 auto I guess it probably makes the case for a person not to use contaminated brake fluid.

01-01-2007, 08:55 AM	#7
Palf70Step State of Confusion! Join Date: Jul 2002 Location: Gulfport, MS USA Posts: 47,216	Re: locked up 80 GMC 6 auto I would flush the system of all fluid, replace the rubber lines, inspect the calipers. Refill and bleed the system then see how things work. Your rears could be rusty, but not be bad at the front. Yours is acting just like my 82 did with the proportioning valve, which was the first time I ever heard of one going bad. __________________ 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!

01-02-2007, 10:17 AM	#8
marvxyz1 Registered User Join Date: Oct 2005 Location: Pittsburgh, Pa Posts: 106	Re: locked up 80 GMC 6 auto Thanks for the info palf70step I'll follow your advice marvxyz

01-02-2007, 02:57 PM	#9
marvxyz1 Registered User Join Date: Oct 2005 Location: Pittsburgh, Pa Posts: 106	Re: locked up 80 GMC 6 auto palf70styep, Just one other question --Is the proportioning valve mounted right below the radiator an have 2 brake lines coming dfrom Master cylinder &2 lines going to the front calipers attached to it??

01-02-2007, 03:51 PM	#10
Palf70Step State of Confusion! Join Date: Jul 2002 Location: Gulfport, MS USA Posts: 47,216	Re: locked up 80 GMC 6 auto That's where mine was too. Practice your bad words...You'll probably need them. __________________ 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!

01-02-2007, 03:52 PM	#11
marvxyz1 Registered User Join Date: Oct 2005 Location: Pittsburgh, Pa Posts: 106	Re: locked up 80 GMC 6 auto Why is that?? I doesn't look to intimidating.

01-03-2007, 01:32 AM	#12
Russell Professional Grade Join Date: May 2003 Location: Fort McMurray, Alberta Posts: 7,915	Re: locked up 80 GMC 6 auto Getting the thing off isn't the problem, its getting the brake lines back on that can be rather frusterating, lol I did mine when I had nothing but a rolling chassis, and I spent a few hours on that thing. Gotta make sure you don't cross-thread it, I ruined a perfectly good prop valve doing just that... __________________ 1995 Chevrolet 2 Door Tahoe (6.6L LBZ Duramax / ZF6 / NP241 with 1 ton solid axle swap)

01-03-2007, 06:23 PM	#13
marvxyz1 Registered User Join Date: Oct 2005 Location: Pittsburgh, Pa Posts: 106	Re: locked up 80 GMC 6 auto I removed ny prop valve. and on a scale of 1-10 It was a 7 or 8 . I need to get a new prop valve. Checked with the chevy dealer and they want 169.00. Definately to much. e-bay has some but I don't know if I can use them in my 80 GMC. Example

01-03-2007, 06:25 PM	#14
marvxyz1 Registered User Join Date: Oct 2005 Location: Pittsburgh, Pa Posts: 106	Re: locked up 80 GMC 6 auto I got it off and On a difficulty rating of one to ten I think it was a 7 or 8. Definately not easy. Not my next project will be finding a prop valve. I checked with the Chevy dealer , and they want 169.00. I told them it was to much. I'll have to find it elsewhere. I saw some on e-bay, but I don't know if I would have trouble with installing them, and if they will work. Example=



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