You will find that these trucks have more braking power in the rear than they need, when not loaded. As the rear wheels start to break traction, one will go before the other.
Will this single-wheel-lockup be minimal, and alternate sides, if the brake system itself is flawless? Or is there something systemic in the design that will favor 1 wheel when excess braking is applied under a light load?
I'm just guessing, but it seems like it shouldnt take too much more braking to get the second rear wheel to lock up?
My truck does not do this, but I have the original single resovoir MC, and the 1 wheel/3 wheel brake line distribution that Cletis decscribes, so I dont think the same physics apply to my truck that John Hill is having.
John, your original post sounds to me like it is possible you havent given the brakes a close inspection yet, and are just going by what the PO told you about their repair/condition.
You may not be able to eliminate the rear-wheel lockup problem you are currently having, but my instincts tell me it's worth at least a little more diagnosis to make sure that your case is "normal", and not a sign of a more serious problem, like a line blockage to the wheel that is not locking up...
When my son and I were doing the brakes on our truck, we had the whole truck very securely sitting on jack stands and wooden blocks so that all 4 wheels were safely off the ground. When we were "bench" testing the brakes, Mac would gently apply the pedal while I turned 1 of the wheels. As soon as I felt some resistance, Mac would then hold the pedal steady where it was, and I would check the other 3 wheels to make sure they were getting equal resistance. We worked our way from low resistance, to lock-up, and I used a tire iron to try turning the wheels to make sure I could not turn them. The natural equalization of the line pressure from the single cylinder MC did most of the work, and we only did minimal adjustment of each wheel until I felt comfortable I had acheived my goals of an even braking system.
Now that the truck is on the ground and we ~can~ road test it,
under road conditions, most of the time I have very even braking,
but I have to admit they are not yet perfect... Occasionaly I get a sharp pull to the left from the front drivers wheel.... This is the 1 brand new wheel cylinder in the system, and it is the 1 wheel with it's own dedicated brake line coming from the distribution block from the MC. So, I am still "in the process" of diagnosing and tuning the braking on this old truck.
