The Stovebolt Site Forums The Shop Area Driveline shim under the straight axle

my memory is failing me. Would someone tell me where the shim/wedge goes under the front axle on the AD's. I know it goes under the spring but does it go in from the front of the rear??? Mine is under from the rear and its been aligned but I was under the panel double checkng things when I notice it was under the back....which got me to thinking.

And, also remind me why GM put it under the axle....to tilt it but why???
Its been a loooooong week.

Alvin, the shim goes under the back of the axle.
Simply put, this is done to move the angle of the tires as hit the road outward to ease the steering effort. This is the caster adjustment. Think of a bicycle or even a motorcycle. In both cases the forks are slanted outward at the bottom to ease the steering. It's a little more important on a two wheel front end so that the caster of both wheels are adjusted the same. It has an effect on the ease of the steering and on the tire wear.

Hi Alvin,,,theyre for the tilt of the axle, to lean it forward or backward. They come in (i think) 2 degree increments. As 6cylovertexas said, theyre important for ease of steering.
I have a couple if you need a couple.
Marty

Like the guys say Alvin,these caster shims are there to fine tune the geometry.

These affect the KPI (king pin inclination)
Generally if the axle(king pin) is tilted forward at the top in relation to the rest of the truck,the steering would become lighter and more prone to wander,it's self centering ability is reduced.
i.e. If you were to turn a corner and release your grip on the wheel it would continue turning.
Whereas if it were tilted back it would make the steering slightly heavier but much nicer at speed,the centering will be increased.

When I used to work on lowering VW Bugs where the front was radically lower than the back end we would lose caster,so we would add extra shims(upto 6 degrees)for the same reason.

Alvin, did your alignment guy get it aligned without any issues? If the alignment came out good you should be good to go. I'm sure you know the guy that did yours but I have seen many of the younger guys doing alignments that have no clue how to make adjustments to a straight axle vehicle. Those types set the toe in and send it out the door saying "good enough". Not.

First off thank you fellows for confirming and reminding me of what I "use" to know.

Don, my front end guy,Mike, does alignment on lots of resto's and modified vehicles. I could not believe it when he said he did not have to make one single change on my panel. Caster/camber and toe-end were dead on. I had a conversation with him before doing my panel and was especially interested in the "4 wheel alignment" as I had lowered the rear and also moved the drivers side rear 5/8" to get it to where "I" thought it was good. Plus I had cut off the old stuff and tack welded new perch blocks on the axle. Mike actually complimented me on the work I had done and wanted to know how I had done it. I simply told him the red marks were still on my shop floor when I was squaring it up....and I still remembered how to use a "meauring stick". I had also put new style tie rod ends on the truck and had set the tow in using the old oil can and screwdriver method to get it close from back in the early dirt track racing days! ....... and he only charged me $30 bucks checking it over.
There are still some good guys in this world...like the Bolters I know!!!

I have driven it up and down the street "no tags yet" but the real test will be later this month. or next. when it goes on the main road.
Thanks again fellows.

I need a front axle to spring SHIM for my 39 1.5 ton, angle measures .09" to.19" shim measures 1 3/4 by 3 7/8" can anyone help?

freddyfrakel

Put a post in the swap meet, parts wanted section. You will have better luck getting what you need.

The shims on my one ton had a hole in the center to help keep it in place. The spring center bolt sits in it. They also had a small pin on the rear side that dropped into a tiny hole in the axle to aid in axle/spring installation. You may need to drop the axle some to get the shims in. I had to.

Dozens of them on Ebay- - - -search "front axle caster shim". Several different degree sizes.
Jerry

Thanks, exactly like my shim

Just go to a shop that specializes in heavy truck suspension. A lot of trucks are still using a straight axle.

You can also buy caster shims at NAPA, I think Dorman brand.