Caster Shims, Necessary?

[Jdc1]

Most of the information here is very complete so I’ll only add my latest results. @Jdc1 did a differential swap, bushings, knuckle rebuild, seals, TRE’s, steering arms…in other words a total and complete rebuild. I’d sent along a set of 4* caster shims because the Saginaw power steering conversion was no different then described here…wonky at best and scary at 60/65mph.

The alignment shop confirmed the correction at +3*.

To wrap up a long story…. My truck steers perfectly even at 80mph….(a recent test drive). Another one of the best updates on my 40

Amazing what a dialed in 40 can do.

 

[Vandal FJ]

I have a Saginaw PS and 4 inch springs, no caster shims. I have always been told that caster shims are more necessary when you lengthen the shackles. That's when the caster gets out of whack.

My manual steering box was roached, so that was the biggest issue.

 

[POPO AGIE]

When I got this rig @ 8 years ago the knuckles were redone with the addition of disc brakes. The steering box was rebuilt, center link guts were replaced, and the drag link end was rebuilt . Springs, shackles and bushings 2 years ago. Not sure why I didn’t think of the TREs till lately? They seem to still have life in them after 40+ years!

Mine wandered when it was new. There are to many moving parts. I upgraded to PS with a FJ105 steering box and did a high steer with FJ80 TREs.