help identifying a brake booster

[meathead95]

this is the brake booster that was on my 70 k20 when i bought it and the diaphram went bad in it so i need to replace it. but i have no idea what it came off of. any ideas.

[Bob B.]

From the pictures, it looks like a dual diaphragm Bendix, which was used on '67-'70 3/4 tons.

[rage'nrat638]

ASK FRANK PICKMUP... he knows more about these trucks brakes than anybody i know...he's rebuilt boosters..sell's them rebuilt..seen more brackets and pro valves than 10 of us put together.

he's a site vendor here.. just be nice and i am sure he will steer you in the correct direction.

my hats off to frank..he's the coolest... he sell's many excellent parts and help's people on the board on a daily basis..

[PICKMUP]

Oh Boy, after those good words I will surely screw this up! Bob B is exactly right. That is a 67-70 3/4T dual diaphram booster & brackets...however, it appears that it has a disk brake master cyl bolted to it. Notice the big front chamber.

[chipflyer]

That's a Delco master cylinder bolted to a Bendix booster, correct?


Jeff

[meathead95]

wow! i just new the booster didnt look like any of my half ton trucks or the 3/4ton 2wd trucks that i have ever had. i never imagined it was stock lol...........is it a pretty good booster? as for the master cylinder that is strange as it still has drum brakes. I just changed the axles though to 72 models so ill take that as a plus. is there anyway of telling if the prop valve is for dis drum or drum drum? i was gonna buy a new one but i wonder now if the one on there is disc drum

[meathead95]

do you sell these boosters frank?

[ghetto_superman]

PICKMUP i sent you a pm about somewhat related brake issues

[kevs_c10]

I have that same booster and I've been wondering about it too! Makes sence, the PO of my truck had a 3/4 ton part truck. Thanks guys!

So what should the 1/2 ton booster look like?

[PICKMUP]

I sometimes offer good/exc used boosters & brackets on here, if they pass a vacuum & operational test. I do not rebuild them. You can still get them at your local auto parts, but you do need the correct matching brackets & rod to pedal.
This smaller dual diaphram style is very popular on our trucks because of the size. They are a must for six cyl with 4bbl. The others won't clear.

[meathead95]

what are the proportioning valves from? i called advance, auto zone, and oreilly's and none of them list a proportioning valve for our trucks?

[Palf70Step]

For the pre disk models, I don't think it officially called a proportioning valve . For the 4wheel drum I belive it is xxxxxx block for the name. Be darned if I can remember at this moment. I got from a disk brake proportioning valve from my localk dealer (only place I could find one and NOT cheap) or you can get a generic variable adjust one from folks who sell the conversion.

[meathead95]

i put 72 axles under the truck so i was going to get a valve for a 72 but nobody lists them

[PICKMUP]

MH95: Check with your vendors. They should have the original cast style and the a brass style. Both work fine...or CPP stocks them too.

[meathead95]

thanks frank. is ther a way to tell them apart, or are all the valves for disc drum? the pic i posted already had a disc brake master cylinder on the booster but the truck only had drum brakes. so i was wondering if maybe the prop valve was put on there with the new mc and maybe it is for disc brakes. is there any way to tell.

[meathead95]

does anyone ae a link for cpp i didnt have any luck finding the website

[msgross]

Do you have the measurements for the bolts on that booster? I think that I have the same and they are 3 3/8 wide (center to center) and 3 3/4 tall (c to c). I just ordered one for a 72 1 ton from autozone and it was 3 3/4 x 3 3/4 (c to c) and I returned it. Did these come with disc brakes?

[rage'nrat638]

mine came on a 69 power drum brakes 3/4 ton

i still have power drum brakes

[Farmstore34]

Hey while we're on this subject, how can you tell if the brake booster is bad/failing? My brake pedal seems kinda stiff, and when I push or let off on the brakes the engine RPM increases a little. I think it's maybe leaking internally?
CT.

[msgross]

so what disc MC will bolt up to this booster? It does look like the one I have.

[rage'nrat638]

it's a bendix master cyl with the deep hole in the rear
heres a picture of the booster rod..

as far as i know delco and bendix stuff don't mix

now this picture is a bendix 1/2 ton booster but has the same rod as a bendix 3/4 ton booster

[msgross]

ok. here's my booster. Looks like a 69-70 3/4 ton per above (I know that it's not 72 since I ordered that one from autozone and it was incorrect). I need to order one of these and a MC for disc front end. Does the MC actually matter or is it the prop vs distro valve that matters?

thanks.
Mike

[rage'nrat638]

well i wish i had a answer for you buddy.

that is a bendix booster for sure we know this..

i thought a disc brake master had a bigger piston in it?

and you will for sure need the pro valve for disc brakes

i would just reuse that one..a little work on a wire wheel and it will look new.

as for the master. i have no clue..

what ever master you get it needs to have the deep hole in the back for the long bendix booster rod to fit in it.

if you go on advance auto's web site and punch in the different years of trucks they have pictures of the masters.

or you can get a master for a 69 like mine it will work for sure..

it sure would have been alot easier if they would have only had one MFG of these things..

no telling how many hours have been wasted with people trying to figure out these brakes on our trucks.

p.m. frank and ask what master cyl you need.. you need one like his picture

your pal mark