Do GMT400's typically have crappy brakes, or is it just mine.

[hefftone]

On mine, I can't say that the pedal feel is all that terrible, I just have to push it down all the way to get it stopped. I might have a fast idle (no tach) situation combined with that tight stock torque converter. I'm going to see if it stops better in neutral. I have'nt even had it out on the road yet, just in my neighborhood.

It looks like the Hydroboost setup uses a much larger Master Cylinder bore. 1-1/4"....versus what appears to be 1" for stock..... that alone would make a huge difference in brake pressure.
Will the hydroboost master fit on the vacuum booster?
Looks like Raybestos make a 1-1/8" MC for the vacuum brakes....That would probably help alot itself. They also have a 1-1/4" MC for the C2500 trucks.....if that bolts on it could potentially be a great upgrade.


https://www.rockauto.com/catalog/x,...or+1990+CHEVROLET+C1500+PICKUP+5.7L+350cid+V8

 

[dropped93]

Sounds like you've got a bad master cylinder or worn shoes/misadjusted shoes/bad wheel cylinders or all of the above. Anything with the shoes will cause the pedal to go all the way to the floor..

 

[SixSpeedSS]

My K2500 is even worse at stopping than my K1500 was. I put all new pads/shoes/hardware on it when I bought it, but it still sucks. I think the 2500 has the 1.25" bore M.C. from the factory. My 4 wheel ABS is disabled, but I plan to remove it completely, and replace all lines/hoses. I may go hydroboost as well.

 

[MOBS]

OP, does your truck still have the small brakes or larger brakes like the extended cab? Our trucks naturally have weak brakes in stock form anyways....but by the early 90's, GM had upgraded the regular cab brakes to the larger brakes the ext cabs had.

 

[RHamill]

My rear drums, shoes, wheel cylinders, hardware, front rotors, calipers, pads are all new. I bled the brake system (supposed to do it every 3 yrs, brake fluid is hygroscopic), brake pedal is pretty nice, but still the drums are what is doing it on our trucks.

It still stops better than the 66 GTO we had in the shop with its 4 wheel drums :O

 

[Darkrider]

Best bet to get decent braking in these trucks is retrofitting the hydraboost setup from a Diesel, if I recall right even the 2500 and 3500 gas trucks still have the vac booster. Due to being so used to the vaccum boosted system in my integra and ram I have actually had a couple close encounters with my windshield by slamming on the brakes in my k1500 with its hydraboost and finding out the hard way that they require less pedal effort lol

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[MOBS]

The hydroboost also won't lose the fight against your master cylinder........so it can actually cause blow-by with your fluid. I thought it was my MC needing replaced and got a rebuilt beck-arnley and it'll still do it if you apply enough pedal. Tested MC with brass plugs and it blows by........either crappy rebuild or the hydroboost needs a bypass valve lol.

 

[SixSpeedSS]

My rear drums, shoes, wheel cylinders, hardware, front rotors, calipers, pads are all new. I bled the brake system (supposed to do it every 3 yrs, brake fluid is hygroscopic), brake pedal is pretty nice, but still the drums are what is doing it on our trucks.

It still stops better than the 66 GTO we had in the shop with its 4 wheel drums :O

I got a '67 GTO convertible here at my place with 4 wheel drums and I'd say it stops better than my K2500. If the drums are setup properly, they can stop fairly well. Big issue is brake fade when they get hot.

My '66 GTO has Disc/Drum. I like my car to be safe and drive like a modern car. It stops great.

 

[MOBS]

Both my 67 cougars had 4-wheel drums....if the tires didn't lose traction, it'd throw you thru the windshield!

 

[vipergtrdj]

I also noticed my drums kind of sucked in my K1500, in my 6.5TD K2500 the brakes were awesome. So now I am switching to rear discs in my K1500