3/4 ton master cyl. in 1/2 ton truck? - The 1947 - Present Chevrolet & GMC Truck Message Board Network

Southpa · 06-10-2002, 02:42 PM

Its nice to be home again, staying this time. I want to ask about swapping my master cylinder which is leaking out the cap so much that I have to hang a can under it to catch the "drippings".
Its a 1970 1/2 ton but I've swapped front ends with a 71 so now I have front disc brakes. I installed a 3/4 ton booster and have a 1/2 ton master (leaker) with the single hold-down clip. What I want to do is replace it with a 3/4 ton master (the kind with 2 hold down clips). Any problems with that? Are the line fittings to the prop. valve the same size? Would this produce too much pressure to my front calipers and/or rear wheel cylinders? or are all calipers/wheel cylinders basically the same between 3/4 and 1/2 tons? Any suggestions? much appreciated!

Mike C · 06-10-2002, 07:07 PM

The brake system is carefully engineered for the diameter of the pistons in the rear and in the front. You can get the 1/2 ton master with 2 hold downs. If you do run the 3/4 and I would not, the size of the fittings that screw into it are reversed, just so somebody WOULDN't do that

Longhorn Man · 06-10-2002, 07:43 PM

Plus, out of the 3 trucks I have owned, which gives me 6 master cylinders to date, EVERY ONE leaked like that.
I've tried tightening the clip, but that never seems to help.

1-PU70 · 06-10-2002, 08:45 PM

To get the cover from leaking with the master still on the truck remove some fluid from the master then stuff some rags in it. Take a pice of glass or flat pice of steel and sand the lip around the master till it is smoth. Should take care of any leaks.

>X< · 06-10-2002, 10:16 PM

i'm kinda doin somethig like that,. i'm using discs from my 72 3/4ton on my 1/2 ton project, the people at early classic told me that i could ust the master cyllander if i wanted to, but if i put some rear discs on it i will have to change it anyway, if i use the discs from my 3/4 ton can i use that master cyllinder too?

06-10-2002, 02:42 PM	#1
Southpa Registered User Join Date: May 2000 Location: Victoria, BC, Canada Posts: 2,409	3/4 ton master cyl. in 1/2 ton truck? Its nice to be home again, staying this time. I want to ask about swapping my master cylinder which is leaking out the cap so much that I have to hang a can under it to catch the "drippings". Its a 1970 1/2 ton but I've swapped front ends with a 71 so now I have front disc brakes. I installed a 3/4 ton booster and have a 1/2 ton master (leaker) with the single hold-down clip. What I want to do is replace it with a 3/4 ton master (the kind with 2 hold down clips). Any problems with that? Are the line fittings to the prop. valve the same size? Would this produce too much pressure to my front calipers and/or rear wheel cylinders? or are all calipers/wheel cylinders basically the same between 3/4 and 1/2 tons? Any suggestions? much appreciated! __________________ 1970 GMC 1500 Custom Original 350/TH350 Victoria, BC, Canada You can wish in one hand and crap in the other. See which one gets filled first.

06-10-2002, 07:07 PM	#2
Mike C Registered User Join Date: Dec 1999 Location: Austin, TX, USA Posts: 7,727	The brake system is carefully engineered for the diameter of the pistons in the rear and in the front. You can get the 1/2 ton master with 2 hold downs. If you do run the 3/4 and I would not, the size of the fittings that screw into it are reversed, just so somebody WOULDN't do that __________________ 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

06-10-2002, 08:45 PM	#4
1-PU70 Registered User Join Date: Apr 2000 Location: Bradenton, FL Posts: 1,036	To get the cover from leaking with the master still on the truck remove some fluid from the master then stuff some rags in it. Take a pice of glass or flat pice of steel and sand the lip around the master till it is smoth. Should take care of any leaks. __________________ 1970 CST/10 402,700R4,3:73 posi,AC,PS,PB,TLT,PW,Buckets with heaters

06-10-2002, 10:16 PM	#5
>X< registered IWATA user Join Date: Feb 2002 Location: Baton Rouge Posts: 4,481	i'm kinda doin somethig like that,. i'm using discs from my 72 3/4ton on my 1/2 ton project, the people at early classic told me that i could ust the master cyllander if i wanted to, but if i put some rear discs on it i will have to change it anyway, if i use the discs from my 3/4 ton can i use that master cyllinder too? __________________ -'63 Ford Fairlane 500 coupe, v8, auto, faded and rusty. awaiting built roller 302 and some flat black -'99 Honda Prelude. vtech/5spd. no pipe, no intake, bone stock. awaiting new top end. -01 GMC Yukon SLT 5.3 dented and scratched with a noisy tranny. Take off that Von Dutch hat before i stab you with a 000 Mack.

06-10-2002, 07:43 PM	#3
Longhorn Man its all about the +6 inches Join Date: Jan 2001 Location: Hilliard Ohio Posts: 2,690	Plus, out of the 3 trucks I have owned, which gives me 6 master cylinders to date, EVERY ONE leaked like that. I've tried tightening the clip, but that never seems to help.



Register or Log In To remove these advertisements.

Register or Log In To remove these advertisements.