master cylinder 71 72 disc question - The 1947 - Present Chevrolet & GMC Truck Message Board Network

otef546 · 02-11-2009, 12:51 AM

I went to autozone to get a new master cylinder and they asked all the normal computer questions except if the truck had manual or power brakes.When I questioned him about this he said there was only one part number for all 1/2 ton 71 and 72 and that it didn't matter if it was manual or power.When I look in all the catalogs like LMC , etc they all show two different numbers so what is the deal and who is correct?

thanks Mike

**1970cstblazer** · 02-11-2009, 09:04 AM

NAPA lists the same master cylinder for both manual and power for both 1971 and 1972 1/2 tons.

chris71 · 02-11-2009, 09:42 AM

there is only one, the power booster is only an assist to the braking system that already exist in the truck, power and non power MC's are the same

now, there is a difference between disc/drum, drum/drum, and disc/disc master cylinders because disc brakes require a higher volume of fluid to work, therefore the resivoirs are bigger

badpeanut · 02-12-2009, 01:53 AM

I went to buy a master cylinder for my '72 1/2-ton 4x4 recently and they couldn't decide if it should be a 1-1/8" bore or 1-1/4" bore. Is 1-1/8" bore for 1/2-ton trucks and 1-1/4" bore for 3/4-ton trucks?

otef546 · 02-12-2009, 03:18 AM

thanks for the answers

Mike

Andy4639 · 02-12-2009, 12:26 PM

71 72 trucks should use the same master cyclinder for the right truck.

Chevy truck chassis service manual series 10-30.
Section 5-2:

C,K,P 10 series has manual master cyclinder non booster mounted to fire wall.

C,K,P-20 thru 30 series same as above with vacuum assist booster.

C-30 with H-22 option which shows lines going to the frame booster

P-30 with H-22 Option

This is straight out of the manual.

02-11-2009, 12:51 AM	#1
otef546 Junior Member Join Date: Sep 2005 Location: Beebe Arkansas Posts: 152	master cylinder 71 72 disc question I went to autozone to get a new master cylinder and they asked all the normal computer questions except if the truck had manual or power brakes.When I questioned him about this he said there was only one part number for all 1/2 ton 71 and 72 and that it didn't matter if it was manual or power.When I look in all the catalogs like LMC , etc they all show two different numbers so what is the deal and who is correct? thanks Mike

02-11-2009, 09:04 AM	#2
1970cstblazer All stock and staying that way Join Date: Jul 2003 Location: Elkland, PA Posts: 1,445	Re: master cylinder 71 72 disc question NAPA lists the same master cylinder for both manual and power for both 1971 and 1972 1/2 tons. __________________ 1970 K/5 Blazer CST 4WD, Bronze, 93k ACT. miles, 350, 4 speed, positraction, 16.5" x 8.25" wheel option, tilt, tach, vacuum, AM/FM, manual throttle...Dad ordered and purchased new 4/70. Currently frame off restoration in progress... 1972 Cheyenne Super 20 2WD, DK Blue/White, 90K ACT. miles, 402, TH400, 4.10 open, tilt, tach, vacuum, A/C, AM/FM, manual throttle.. A mostly original paint never rusted Texas survivor... 2017 Sierra 1500 SLT 4WD, Black, 41k miles, 5.3, 6L80E, 3.42 LS, 20" polished wheels, everything but moonroof and 6.2... 2019 Canyon SLT 4WD, White, 60k miles, 3.6, 8L45, 3.23 LS, 18" wheels

02-11-2009, 09:42 AM	#3
chris71 Registered User Join Date: Oct 2007 Location: Sykesville MD Posts: 357	Re: master cylinder 71 72 disc question there is only one, the power booster is only an assist to the braking system that already exist in the truck, power and non power MC's are the same now, there is a difference between disc/drum, drum/drum, and disc/disc master cylinders because disc brakes require a higher volume of fluid to work, therefore the resivoirs are bigger __________________ '55 3100 2nd series short-bed stepside '70 Corvette coupe stingray '71 Chevelle 2-dr coupe SS clone '71 C10 long-bed fleetside '83 long-haired brunette wife

02-12-2009, 01:53 AM	#4
badpeanut Not a bad nut after all.. Join Date: Dec 2000 Location: ND Posts: 1,756	Re: master cylinder 71 72 disc question I went to buy a master cylinder for my '72 1/2-ton 4x4 recently and they couldn't decide if it should be a 1-1/8" bore or 1-1/4" bore. Is 1-1/8" bore for 1/2-ton trucks and 1-1/4" bore for 3/4-ton trucks? __________________ '05 Chevy 2500HD 4x4 '72 GMC LWB 4x2 driver '72 Chevy LWB 4x4 plow truck '71 Blazer 4x4 driver '70 GMC LWB trailer

02-12-2009, 03:18 AM	#5
otef546 Junior Member Join Date: Sep 2005 Location: Beebe Arkansas Posts: 152	Re: master cylinder 71 72 disc question thanks for the answers Mike

02-12-2009, 12:26 PM	#6
Andy4639 Old member Join Date: Jan 2002 Location: Liberty, & Garden City S.C. , U.S. Posts: 19,936	Re: master cylinder 71 72 disc question 71 72 trucks should use the same master cyclinder for the right truck. Chevy truck chassis service manual series 10-30. Section 5-2: C,K,P 10 series has manual master cyclinder non booster mounted to fire wall. C,K,P-20 thru 30 series same as above with vacuum assist booster. C-30 with H-22 option which shows lines going to the frame booster P-30 with H-22 Option This is straight out of the manual. __________________ 1971 LWB Custom, 6.0LS & 4L80E, Speedhut.com GPS speedometer & gauges with A/C. 20" Boss 338's Grey wheels 4 wheel disc brakes. My Driver Seeing the USA in a 71 Upstate SC GM Truck Club 2013,14 and 2016 Hot Rod Pour Tour http://upstategmtrucks.com/ Get out and drive the truck this summer and have some fun! It sucks not being able to hear! LWB trucks rule, if you don't think so measure your SWB! After talking to tech support at Air Lift I have found out that the kit I need is 60811. Per the measurements I gave them. Ride height of truck inside spring and inside diameter of springs.



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