[SEL] OT - 3/4 ton truck question (for the pros) Help pleasE?

[bill at antique-engines.com]

That's my initial thought. The brakes themselves are easily moved - the
calipers can be slid by hand, the pistons are free. If there was much out
of parallel, the outer surfaces on each/both rotors would not have been
well under spec, IMO. If the outer surfaces are true, that means any out
of parallel would have to be fully and totally on the inside surfaces.
Hard to imagine, possible I suppose, but hard to imagine the outer
remaining true while the inside only warps, esp with smooth moving
calipers that move freely. Non-scientific, but I did move the calipers and
pads to the point where they JUST touched the rotor surfaces and spun the
rotors by hand - you didn't hear a touch, no touch, touch, no touch sound,
it was solid and constant, touching consistently with each rotation.
I'm quite familiar with spring wrap - my 68 Javelin suffering major
wheel-hop solved with slapper bars on the leafs.
Torque links with new bushings solve the issue on my current 1970-
Javelin, not to mention new HD semi-elliptical springs on the rear.
When I come to a stop slowly and just rest my foot on the pedal with real
light braking, I feel no pulsation in the pedal at all - not even the
slightest. The pedal is always smooth and firm with no pulse.
The steering wheel doesn't shake side-to-side either.

It's just a weird, hard to describe thing. And although trained as a
mechanic in the 70's and working front ends and suspension for years, I
never really dealt with trucks at all (other than changing kingpins and I
hated that!), and got out of the business in the early 80's before this
design.

Bill


>>
>
> Being a solid axle truck gets you away from the common C bushing problems.
>
> First replace ALL the spring bushings. What your feeling could easily be
> caused by the bad bushing allowing the spring to shift under braking.
> Especially when it comes/goes with braking, and the front bushing is bad.
> What you are feeling is essentially the same thing as spring wrap in the
> rear of a leaf spring hot rod. You step on the brake and the axle reacts
> by trying to twist. With the bad mount the spring can move farther and
> then the spring returns and what you feel is the oscillation of the
> spring.
>
>
> --
> Steve W.
>
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