1/2 or 3/4 ton master cylinders - The 1947 - Present Chevrolet & GMC Truck Message Board Network

68 Suburban · 08-29-2002, 01:29 AM

Is there a difference between the 1/2 and 3/4 ton master cylinders on drum brakes? If there is, what would happen if you put a 3/4 master on a 1/2 ton truck? Thanks

Longhorn Man · 08-29-2002, 01:48 AM

I'm not certian, but I know the one tone is not the same as 1/2 ton.
I think the resivors are swapped around...still dunno what would happen though.

colohusker · 08-29-2002, 01:49 AM

Let us know how it works Chris!

I show different part numbers between the 1/2 and 3/4, but the 3/4 has the same # as the 1 ton.

Scott

68 Suburban · 08-29-2002, 01:58 AM

Im trying to figure out if I would get more pedal preasure with the 3/4 ton cylinder, but I don't want to do anything to mess with my safe braking

JimKshortstep4x4 · 08-29-2002, 07:29 AM

We have used both 3/4 ton and 1/2 ton master cylinders with no observed differences. The boosters are different because the 3/4 ton has double diaphragms. Sometimes we have used 3/4 ton
master cylinders because the 1/2 ton will not fit the booster on the truck.

Here is a web site with some information on boosters:

www.brakeboosters.com/booster.htm

Jim

Mike C · 08-29-2002, 07:53 AM

A good parts store should be able to give you stroke and piston diameter info from their book. The fittings on the master cylinder are reversed, at least on the 3/4 ton disc master vs. the 1/2 ton disc master, I assume this was to PREVENT someone from putting the 3/4 part on the 1/2 truck. Your call!

JimKshortstep4x4 · 08-29-2002, 08:16 AM

We have not seen the difference that Mike pointed out. It could be that changes were made before we got the trucks. As Mike pointed out cylinder size information is available at the parts stores, (at least in our area). There is a good article in the latest Carcraft on brakes and it covers a lot including line pressure information.

Jim

1-PU70 · 08-29-2002, 10:31 AM

From what I have seen the lines that come out are reversed on 1/2 and 3/4 and the 3/4 uses a shorter rod from the booster.

08-29-2002, 01:29 AM	#1
68 Suburban Registered User Join Date: Oct 2000 Location: From Chicago, Live in Phoenix, AZ Posts: 6,802	1/2 or 3/4 ton master cylinders Is there a difference between the 1/2 and 3/4 ton master cylinders on drum brakes? If there is, what would happen if you put a 3/4 master on a 1/2 ton truck? Thanks __________________ Just sitting here contemplating contemplation.

08-29-2002, 01:49 AM	#3
colohusker Registered User Join Date: Apr 2002 Location: Longmont, CO Posts: 436	Let us know how it works Chris! I show different part numbers between the 1/2 and 3/4, but the 3/4 has the same # as the 1 ton. Scott __________________ ------------------------------------------------ I say it's only money, my wife says it's only a truck.... '71 C10 Deluxe, factory ac, ps, pb, should be done by 2102 Longmont, CO husker95@hotmail.com Last edited by colohusker; 08-29-2002 at 01:55 AM.

08-29-2002, 01:58 AM	#4
68 Suburban Registered User Join Date: Oct 2000 Location: From Chicago, Live in Phoenix, AZ Posts: 6,802	Im trying to figure out if I would get more pedal preasure with the 3/4 ton cylinder, but I don't want to do anything to mess with my safe braking __________________ Just sitting here contemplating contemplation.

08-29-2002, 07:53 AM	#6
Mike C Registered User Join Date: Dec 1999 Location: Austin, TX, USA Posts: 7,715	A good parts store should be able to give you stroke and piston diameter info from their book. The fittings on the master cylinder are reversed, at least on the 3/4 ton disc master vs. the 1/2 ton disc master, I assume this was to PREVENT someone from putting the 3/4 part on the 1/2 truck. Your call! __________________ 44 Willys MB 52 M38A1 64 Corvette Coupe 68 Camaro 'vert LT1 & TH700 69 Z/28 355 12.6's @110 69 Chevy Short Step 4 1/2"/7" drop 72 Jimmy 4WD 4spd 4" & 35's 02 GMC 2500HD 4x4 Duramax

08-29-2002, 10:31 AM	#8
1-PU70 Registered User Join Date: Apr 2000 Location: Bradenton, FL Posts: 1,036	From what I have seen the lines that come out are reversed on 1/2 and 3/4 and the 3/4 uses a shorter rod from the booster. __________________ 1970 CST/10 402,700R4,3:73 posi,AC,PS,PB,TLT,PW,Buckets with heaters

08-29-2002, 01:48 AM	#2
Longhorn Man its all about the +6 inches Join Date: Jan 2001 Location: Hilliard Ohio Posts: 2,693	I'm not certian, but I know the one tone is not the same as 1/2 ton. I think the resivors are swapped around...still dunno what would happen though.

08-29-2002, 07:29 AM	#5
JimKshortstep4x4 Senior Member Join Date: Jul 2001 Location: Muskegon,MI,USA Posts: 6,026	We have used both 3/4 ton and 1/2 ton master cylinders with no observed differences. The boosters are different because the 3/4 ton has double diaphragms. Sometimes we have used 3/4 ton master cylinders because the 1/2 ton will not fit the booster on the truck. Here is a web site with some information on boosters: www.brakeboosters.com/booster.htm Jim

08-29-2002, 08:16 AM	#7
JimKshortstep4x4 Senior Member Join Date: Jul 2001 Location: Muskegon,MI,USA Posts: 6,026	We have not seen the difference that Mike pointed out. It could be that changes were made before we got the trucks. As Mike pointed out cylinder size information is available at the parts stores, (at least in our area). There is a good article in the latest Carcraft on brakes and it covers a lot including line pressure information. Jim

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