I've got my 86 GT in the shop for an alignment and their unable to do it due to large changes in toe at the front when lifting or pulling down on the car, several degrees each way. Any clues what could cause this?

How many degrees of toe in when raising/toe out when compressing front suspension is considered normal?

I don't know what is normal, but I would expect some would be normal.
Typically the front end is bounced up and down to settle the suspension, and when settled, the measurements/adjustments are done. If the readings are inconsistent after settling, look at the inner tie rods.
If the readings are consistent, find another shop.

OK, so I took the car to a different shop, and had it put on a Hunter Hawkeye rack.

They were able to put the rear in spec for me, however the front was another matter.

The front right was able to be set to the correct camber easily enough, however on the drivers side, the closes they could get it was -1.16deg.

Additionally, the camber on both sides was ~1.5 degrees.

They've set the passenger side to match the drivers side so at the moment I've got ~1 degree negative camber on the front.

I'm positive that the guys working on the rack are competent as we spent a good while talking about it and I trust them.

I think the issue with the camber on the drivers side is down to the upper arm pivot; I had tried to replace the upper arm bushes on that side before I took the car off the road a few years ago and didn't manage to get the pivot bolt out. I suspect I made the problem a lot worse beating on the pivot and I reckon it's somewhat bent up now, pulling the arm in/up from where it should be affecting the camber as a result.

I'm going to have another crack at getting the pivot out now that I have more of the right tools, more experience, and more determination. I think I can resolve this one

On the passenger side though, I'm pretty certain that the bushing is in good shape (when I replaced the upper ball joint on that side a few weeks ago, the arm showed resistance and elasticity bouncing back to its neutral position after moving it around). Other than replacing that upper joint and the outer rod end, I've not had the passenger side apart since I owned the car. This concerns me a little, as I can't imagine how the caster angle would be so far off spec, and consistent on both sides, without having been set delberately. I haven't looked at the position of the washers yet, but I'm hoping that at some point a PO had replaced the upper arm bushes and put the washers back on the wrong end.

Can caster go out of spec to that degree naturally over time? Is there any other issue which could cause such a big, but consistent, change?

I think the caster (and perhaps in a small way the camber) is the main reason for the excessive bump steer - it certainly appears that the tie rods have a downward inclination compared to the lower arms, which would cause the effect I saw at the first alignment shop.

My only other thought there might have been that I might have got the wrong outer rod ends, with longer studs than they should have; does anyone know if rod ends meant for the rear would fit in the front but with the wrong geometry?

84-86 Front caster will not go out for most reasons.
Can be:
Bad bushings
Lower car
Bent UCA LCA or both
Wreck frame, front cross-member, or both.
bent knuckle/spindle
a combination of any or all of the above.

Note: The UCA long bolt must have 12mm Total thickness for Caster washers.
See my Cave, Control Arms

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Dr. Ian Malcolm: Yeah, but your scientists were so preoccupied with whether or not they could, they didn't stop to think if they should.
(Jurassic Park)

The Ogre's Fiero Cave (It's also at the top and bottom of every forum page...)

Toe in is the biggest contributor to tire wear and mishandling. Camber is second, but pretty minor...some cars have inches of camber. Caster really only makes the car stable at going straight ahead, and returning to center after a turn or curve. I normally add a few degrees of caster over factory specs if possible to make it MORE stable going straight. If caster and camber are the same on both sides, really the numbers dont matter that much.

If they settle the car and adjust the alignment for straight ahead, the rest should really be immaterial. If that changes when the car is moved around and returned to straight ahead, something is loose or worn.

[This message has been edited by rogergarrison (edited 07-20-2015).]

Roger, the biggest issue I'm facing is the bump steer at the front. Caster would affect that, however I'm surprised it makes as big a difference as it appears to be doing. This is why I'm wondering about the rod ends....

I definitely have got some issues with the drivers side upper, so I have to sort that out whatever I do, and the steering has to be returned to centre for the last 30-45 degrees of steering wheel rotation dependent on road speed which I know the caster will help with regardless.

On my car the right front either sustained damage when it hit a parked car or someone hit a big pothole because they couldn`t adjust the caster on that side
and when I measure from the middle of the spindle back to a point on the frame the right side is set back about 3/4"
So, in essence the right wheel doesn`t have much stability and the left is set right causing them to work against one another.
I`m going to have someone weld some brackets to each side of stock and redrill the holes to get the lower a-arm back where it belongs.

On the early Fieros caster isn't an adjustment but actually how it's assembled, the placement of washers on the bolt. It should never change unless there is trauma damaging other things.

There is essentially no adjustment to camber from the factory. You can use adjustable ball joints, but like Ogre said when the car is lowered about the best adjustable balljoints can do is return things to 0. I had to make some adjustments with a Dremel to get camber to a desirable point.

I've got adjustable upper joints, I'm happy enough that there is a problem with the upper arm bushings/pivot on the side with the issue.

WRT the bump steer issue, my current thinking is that I may have the wrong rod ends, which are causing the angle of the tie rods to be incorrect (this would explain the issue quite nicely).

My question is, if I had accidentally bought rear outer ends, would they fit on the front (with the wrong geometry) or are the stud or threaded ends different?