parking brake

my parking brake only works when its loaded with a heavy load 1200 what need to be adjusted what where which way its a 85 4x4 shrtbd 5 speed 1/2 ton

Reply to
bja
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You need to adjust either the parking brake cable, underneath the cab, or the proportioning valve, on the frame above the rear axle.

The parking brake cable tends to stretch a bit over time, so you have to take up the slack by tightening it. The proportioning valve increases the braking pressure to the rear axle, the heavier the load you carry.

Reply to
Ernie Leimkuhler

That is counter intuitive. The Parking Brake should work WORSE under heavy loads. To say it ONLY works when loaded is backwards from the way it should normally work. In a perfect world, it should work the same under all loading conditions, but the laws of physics prevails over logic in this instance.

Reply to
Jeff Strickland

But Earnie, his report is that the brake works when the truck is heavily loaded. This would tend to suggest the brake itself is adjusted okay.

I have to wonder if he is altering his use of the brake when the truck is loaded -- it has a load so he yanks the handle harder. If so, then perhaps he is not yanking the handle hard enough when the truck is not loaded.

Reply to
Jeff Strickland

The parking brake should work the same whether the vehicle is loaded or not. If the parking brake does work only with a heavy load I would take a good look at the frame to make sure it is not rusted out and flexing. If the frame is sagging due to rust it would cause the parking brake cable to tighten up and act as you described. If no problems are found, first make sure the rear brake shoes are properly adjusted and the praking brake levers and cables move freely. If the parking brake still doesn't hold then you can adjust the cable.

Reply to
Mike

But, his report is that the Parking Brake works BETTER on a heavy load than a light one.

Reply to
Jeff Strickland

For a short while I had a 86 4WD axle on my 86 2WD truck.

It did give me more torque, but I never came up with a good solution to the parking brake incompatibility between 4WD and 2WD.

2WD toyotas use a separate cable to each rear drum, while 4WD toyotas use a single cable that links both drums.

It had the same problem in that the parking brake only really worked when the truck was heavily loaded.

It has to do with the geometry of the rear axle and how loading the axle shortens the brake cable. The parking brake is supposed to grab harder under a heavier load.

I think if you tighten the parking brake cable at the tensioner under the cab, it will solve your problem.

Reply to
Ernie Leimkuhler

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