Hello -
Finished converting my '57 Chevy 3100 from a TH400 to a 4spd and took it on it's inaugural ride. Everything seemed to be working fine, although it truck seemed a bit sluggish. Whatever, I though, I'm not used to the gearing yet, and I have 2.73s in the rear.
But it kept getting worse...like I was pulling a heavy trailer.
Then I started to smelled something burning.
Uh oh.
Got out of the truck, and ALL 4 brakes were smoking, and the brake lights were stuck on. Pedal seemed a bit firmer than usual.
Limped the truck home, and got it up in the air. Came in this morning, all the wheels spun freely, so I pulled the tires, got under the truck, and inpected all the lines, thinking maybe I damaged one when I was getting the tranny in place. No kinks anywhere that I could find. MC full of fluid. Parking brake wasn't engaged. Brakes lights worked like they should. Pumped the brakes for a minute with the car up in the air. Brakes released as they should, and the brake light worked as it should.
Here's the setup I've got: The PO installed a dual well MC with front discs, looks like a Speedway kit. The MC is still under the floor and uses the factor pedal and linkage. Both lines from the MC feed into a non-adjustable proportioning valve, and the brakes lights are actuated by a pressure switch that's plumbed into the lines feeding the front brakes. Rear end is stock with drums from a 72 - 73 full size Pontiac. When I got the truck, the brakes were shot, so I did a full brake job including cutting the front rotors, new front pads, complete new hardware on the rear, new shoes, cut the drums, and a new wheel cyl on the pass side (leaking). Brakes bled out fine and worked as they should. Previous owner did not have any of the e-brake hardware installed, so I reinstalled the complete ebrake system, including all new cables and hardware. Ebrake works as it should, holds the truck on a hill and disengages smoothly.
Before I did any of the work, the brakes did work, but the pedal sank to the floor because of the leaky wheel cyl. Other than the parts mentioned, I did not touch the MC linkage or pedal.
The only thing that I can think of that's bad is the proportioning valve. This one one of those solid units that you can get on Ebay that has a provision for a pressure switch. Can proportioning valve go bad and cause the brakes to lock up?
When I did the brake job, the MC well feeding the rears was empty because of the leaking wheel cylinder. Any chance some moisture could have gotten in there are corroded the inside of the proportioning valve?
I took the truck for another ride this morning, and the same thing started to happen, and it got worse the more I drove the truck.
If not, any ideas what would cause all 4 brakes to lock up? Everything seems to be in order, so I'm stumped.
Thanks...
Chris
