Need more braking!!!

[bitchin4x4]

Ok, I have been going through all the posts that I have been able to find in regards to increasing my braking ability. I am not sure which way to go here.

I have 72 GMC Jimmy with the stock 1/2 ton MC and booster. I have 3/4 ton 14blt ff rear and dana44 front with the 3/4 ton brakes all around. I replaced all the front brakes parts; rotor, calipers in front and rear brake cylinder and pads and seals!

When pressing on the brakes I have to stand on the brakes to stop on the road, and really hairy going down hill.

To my recollection I don't recall EVER being able to lock up the tires to skid.

Should I replace the master cylinder and booster and if so go to the 1/2 ton or should I upgrade to a 3/4 ton to accomodate the 3/4 ton brakes?

One interesting thing I did read was making sure the vacuum hose to the booster was the correct type, I will have to check that out.

 

[Triaged]

3/4 MC is the same size as a 1/2 ton...so that won't get you anything. If the booster is working you should have a softer peddle and after turning the truck off it should get harder after a few pumps.

The other thing you could try is switching brand (or type) of brake pads. I have had good luck with Raybestos Brute Stop pads. The have higher friction than most. I know Bob K has had problems stoping as well. I can lock up all 4 without much effort on pavement...even with my 36" swampers. I put on a new booster not long after buying the truck.

 

[bitchin4x4]

Thanks for the help.

I will give that a try. I have bled the brakes several times and even took it in to have it done because i thought i wasn't getting it done, point being the pedal is almost too soft and it goes near to the floor but not like the MC is going out.

I am running pads from NAPA and don't recall what they were. I will have to check what they carry again.

Not to mention I need to recheck where the vacuum line is running into, either the intake or carb.

 

[Greg72]

Yep, check that DAMN vacuum hose!!! /forums/images/graemlins/thumb.gif

Night and Day difference when the hose acutally WORKS and provides vacuum-assist like it's suuposed to.

Sometimes it acutally IS the little things....... /forums/images/graemlins/thinking.gif

 

[Burt4x4]

I have heard/read that you can get a 'dual' diaphram booster from a Suburban/ 3/4ton LWB 4x4. Our Blazers have the 'single' diaphram booster, from what i've been told. I have never done this swap so this is all here-say....
Good Luck

 

[TONYP]

first thing...I like your truck color /forums/images/graemlins/thumb.gif /forums/images/graemlins/eek.gif/forums/images/graemlins/thumb.gif

I still need to get to this, if you go to your chevy dealer and ask him about the old motorhomes 4 wheel disk master cylinder (g30?) from the late 80's I have been told that it should work for us, it's made for 4 wheel disk brakes... /forums/images/graemlins/thumb.gif

 

[khotmer]

yeah what is the name of that color...(and for you smart A$$es i know it is yellow!) /forums/images/graemlins/smile.gif

 

[TONYP]

I used the H2 yellow... /forums/images/graemlins/tongue.gif

 

[arq]

use good brake pads. i replaced everything (master, calipers, brake pads, lines, combo/prop valve, etc) on a 72 that i had and the last thing i re-replaced were the front brake pads. never again will i go with the cheapy stuff. darn thing stopped like it should. I got some from napa, it was the best they had.

ARQ.

 

[Triaged]

If the peddle is too soft you can rule out alot of things.
It isn't the booster (or you didn't need it anyway)
It most likely isn't the pads

Things I would look for with this new info...
Check that the rear brakes are adjusted.
Your brake lines might be swelling (good time to upgrade to some braided SS lines /forums/images/graemlins/thumb.gif)
Check that nothing is leaking (pull back the dust boots on the wheel cylinders and on the calipers and look for fluid)
Check your wheel bearings. If they are loose the wheel/rotor can wobble back and forth knocking the piston back in and taking up alot of travel to make contact with the rotor when you step on the brakes....

That is all I can think of for now...try those.

 

[bitchin4x4]

It is a clear coat with yellow tint. If I had to do it again I would buy a color I could get off the shelf. But I like the color!
/forums/images/graemlins/cool.gif

 

[bitchin4x4]

well I have the braided lines up front. I will have to dig into the rear brakes again to make sure what is going on back there.

Now that I am thinking about it the brakes have always sucked on this even before I switched out front and rear axles and went to bigger tires so it has to be something from the MC, booster, proportion valve or lines atleast what I am thinking

 

[bitchin4x4]

well doing my homework I see that the combination valve... the valve itself is a combination of: 1) the metering valve, which will not allow the front disc brakes to engage until the rear brakes are in contact with the drum.

so that would coincide with what you are saying. I suppose I ought to check the rear brakes!

Thanks!
sean

 

[Greg72]

Well......call me slow, but I just realized that

Bitchin4x4 = Sean Lozensky


What's up Sean? I used to spend a lot of time over at Lozensky.com checking out all the truck pics and getting ideas....looks like all that is changed these days...do you have all those gallery pics posted somewhere else now????


/forums/images/graemlins/cool.gif

 

[TONYP]

just talked to the chevy man...
part # 1257225 (proportion valve...)
it's from a P30-60 truck that was a one ton ether lunch or utility truck and had 4 wheel disk brakes, they didn't have one in stock for me to look at but the guy said it will work...
I'm going to try to get to another Chevy or GMC dealer to look at one... /forums/images/graemlins/thumb.gif

 

[bitchin4x4]

That would be me! What's up?

I have the pics still but I have to spend some time and setup a new gallery. I think in the meantime I am going to post to my webshots gallery user "sean4x4" I will add that to my list of things to do here.

l8rz
sean

 

[NITRO]

i have the exact same problem as u do with your brakes. so...i think im gonna adjust my rear lines bcuz i know that they aint even coming close to hittin that drum n e time soon.

NITRO