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

Steve W. falcon at telenet.net
Wed Jul 29 23:00:12 PDT 2009


Bill Dickerson wrote:
> Sort of OT, sort of on. I do pull my flat bed with tractor and engines
> around and haul engines in the back..........
> OK, 1995 Ford F250 3/4 ton 4x4 with 315 and automatic. Probably a heavy axle
> as it's got the larger of the lockout hubs on it - found that out when I
> busted a lockout 4 years after buying it. IT took the larger one.
> 
> Brakes new about a year ago, tires not too bad, recently rotated. New pads,
> rotors turned. 
> Was pulling a trailer with it when I realized that when you hit the brakes
> it felt like the left front was shaking or rather "jerking" back and forth,
> almost like a grabbing brake or a warped rotor, but then not really. Hard to
> tell for sure, but really felt like left side. Wouldn't go away with time,
> and it only does it when braking. Going down the road, turning, etc. no
> issues, good solid ride, but brake and it is almost scary.
> It does it with no trailer on behind now too.
> I raised the front end, pulled the wheels/tires and put my dial indicator on
> the rotors. Left side almost .001" runout, right side .0005" runout (note 3
> zeros so not even 1 thousandth)
> Rotors and pads still look great and I was able to easily move the calipers
> back so I could spin the rotors. The calipers move smoothly with only hand
> or screwdriver. Nothing is stuck, rotors are really true, tires look ok.
> So I crawled under it and found the spring bushings are really weathered and
> cracked. Well, it's a 95 so it's almost 15 years old. But then I shone a
> light up into the front shackle area and found the top bushing for the left
> front spring shackle was really shot - in fact, bolt to metal, the bushing
> is split and moved away.
> Question - is that what I'm feeling?
> If this was a car I'd feel confident - I did front suspension work to help
> get through college and did many dozens of front end alignments and rebuilds
> and it was a full quarter in college, but I'm so out of touch with the
> larger trucks and their suspension and behaviour.........
> 
> Thoughts????
> 
> Bill
> Runnells - cold and dry, record cold July
> 
> 
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> 

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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