1995 F250 PSD 5-speed, 148,000-ish miles, Dana 50 front axle

The truck pulls to the right. Not jerk-the-wheel-outa-your-hand hard, but enough to keep you on your toes. So far:
* Suspension and steering ball joints are all pretty fresh. She just bought the truck, but the records show they were done recently.
* Alignment is dead-on. Alignment shop said nothing is bent, out of place, etc, and confirms the ball joints are in good shape, and nothing else is worn.
* Tires have been rotated every which way. I don't know the exact pressure, but they're all aired up to the same number
* Shocks are fairly fresh, within a year or so. I'd have to check the records, but no more than a few 1000's miles on them.
* This has been happening for some time. Previous owner brought the vehicle into the dealer with this complaint. They checked/did pretty-much the same things (alignment, swapped tire positions, etc), and couldn't eliminate it.

I don't think it's drag. There's a bit of brake drag, but not enough to make it pull like this. And neither wheel bearing sounds bad.

The body seems to ride a bit lower (about 1/2") on the right side. I wonder if the leaf spring on that side is just more sagged out. Could that account for the pull? Does anyone know if the springs are the same left-to-right? I wonder if it'd be worth swapping them, just to test.

The alignment shop suggests setting the caster OFF by about a degree. They claim that won't have an effect on tire wear or any other steering/handling characteristics, and that it'll be safe. True?

Any other ideas?

 

after a decent drive, see if one wheel or two feels hotter then the others, especially around the hub area. Your brakes might be dragging more then you think.

 

Thanks for the tip. I've got one of those IR "point and shoot" thermometers I can use on it. They're not very accurate, I know, but it should at least point out a significant difference in temp.

 

Many times, a pull can be contributed by a change in the wheelbase. What I mean by this, is that if a spring bushing in the rear goes bad, and the axle is permitted to move only a slight amount, you will encounter a pull.
Probably a long shot, but dont rule out something in the rear.
Weak, or even a broken spring can also result in a sag, and if the shackle angle is different from side to side, the wheelbase can also be slightly different, and will also cause a pull.

 

Well, I measured the wheelbase like this:
Rear:

to Front:

This shows the left side, at 134 and 1/8". The right side is actually about 5/32" MORE than the left (thus 134 and 9/32"). Is that enough to cause a pull? And it seems to me it should be the opposite; I was expecting the right side wheelbase to be LESS.

Next question is, why is it different?

 

no that shouldnt be enough to cause a pull like you describe.

are all your tires the same pressure?

are you dead sure your balljoints are tight?

check ALL your bushings... including the pivot points under the engine and your leaf spring bushings

yes the rear springs are interchangeable... you could swap them around to see if that helps.

do you have any history on this truck? if not you might want to crawl under and see if maybe it has been in an accident that could have tweaked the frame. if the frame is tweaked even just a little bit it could cause some pretty bad effects depending on where its bent

-cutts-