Brake system help needed!

Chevycrew

Well-Known Member
Location
WVC, UT
Ok here is the run down.

99 K2500 with a 7.4L

Originally Hydroboost with 3/4 ton master cylinder, and IFS

Swapped in a 79 HP 60, dual piston calipers, all is good.

Swapped on chevy 3/4 ton rear calipers for disc swap, all is good.

Round 2-

Went to rockwells drum brakes, low pedal but firm, not great but it would stop.

Round 3- The fun part!

I didnt like much about the truck, so I swapped in a 86 ford hp 60 with dual piston calipers, and a rear axle from a 2002 chevy with dual piston calipers. I removed the hydroboost due to leaks, and I didnt like the steering and brakes sharing the pump. ABS was also tossed out.

Currently it has a vacuum booster from a 1998 suburban, and the matching master cylinder (1/2 ton brake system). Front brakes are hooked to the large reservoir side (Closest to the brake booster.)

I have a low, soft pedal, and cannot lock up the tires (37's)

All brakes are straight off the master, no prop valve, or ABS.

Booster is working good, Master cylinder is off my toyota, worked good on there with a 3/4 ton chevy calipers front and rear.

On a test drive, all 4 rotors are getting warm, more heat in the fronts than rear.

I have already tried a 2002 2500HD chevy disc/disc master (originally off a hydroboost truck, but it may have been hooked up wrong, I had the rear brakes on the rear of master, closest to the booster, and the front on the front. It shares the same reservoir so I didnt notice when it was hooked up.

My wifes truck has the same booster, master, and rear axle. Instead of the ford dual piston calipers up front, it has gm 3/4 ton. It has great brakes with 40s.

So any ideas? What master do I really need?



P.S.

I still have the original 3/4 ton master from my truck I can try as well.
(If really needed I still have all the hydroboost too.)
 

crawldaddy

Active Member
Location
Logan
I have the exact same symptom. I'm looking forward to see what others suggest. I have almost the same axles with the same tire size. Ive been fighting this for months and am about ready to give up.
 

lewis

Fight Till You Die
Location
Hairyman
Got lost 3/4 the way through.
running 1 tons I had low soft pedal and couldn't lock up the tires. Went with a 1 ton t100 MC and firm pedal now and the rears lock up, now need proportioning valve for the rear.
 

Chevycrew

Well-Known Member
Location
WVC, UT
I also have a buddy who is running the same 1/2 ton booster and master as I currently have, with Dana 60 dual piston calipers, and a disc 14 bolt in the rear.

His brakes are good.
 

Chevycrew

Well-Known Member
Location
WVC, UT
Ok quick rundown for those who want it simpler.

99 k2500 crew cab.

1986 dual piston caliper dana 60 front
2002 dual piston caliper 14 bolt rear

I swapped from hydroboost to vacuum.

I tried a 2002 2500hd master, 1.45" bore, low hard pedal.
I tried a 1993 1500 master, 1.125" bore, low soft pedal.

Next to try is the stock 2500 master to my truck, it is a 1.25" bore and just may be whats needed, but I really dont know.
 

Chevycrew

Well-Known Member
Location
WVC, UT
Well Im back the 2500hd master, seems to work decent? Im not happy yet, but I can live with it. It will almost lock the rear tires now, and nose dives pretty good.
 
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