The Stovebolt Site Forums The Shop Area Driveline Stepside axle shim to level my 1956 3100 truck

After my install of the side mount spare tire and fender (my truck didn't originally come that way) I see that the truck sits a little lower on the left side. I'm looking for a source for the shim that goes between the axle mount and bottom of the left rear spring to level it up. It's meant to restore the truck stance from the shift of the spare tire weight from the rear center of the truck to the left side.

Editor Note: This thread originated in the Swap Meet Truck Parts Wanted forum, but has been given minor edits to move it to the Driveline forum to save/share the technical info related to the project for fellow Bolters to see and share.

Mickey - A 1961 Chevrolet Master Parts book shows the spacer as GM# 3721152 (no dimensions given) as shown in first pic below. A more detailed part description found in a 1963 GMC Master Parts book showing the same GM# 3721152 gives the following dimensions:

Spacer - 2" wide x 4" long x 1/2" thick with 1 each 33/64" diameter hole in center.

If you can't find an original, those specifications should be enough to fabricate a spacer to fill your need. You will need new (and possibly longer) spring to axle u-bolts to install. Best of luck in your hunt!

Is your rear axle above or below the leaf springs?
If the rear axle is above the leaf springs like 47-55.1, you need to put that spacer on the side opposite of the spare tire. It will lower the right side to match the spare tire side (left side). It is a "lowering block".

Carl 1955.2-59 1/2tons have below spring mounted rear axles. Spacer for Mickey's 1956 truck needs to go on the drivers side. Not a "lowering block" in this instance.

as long as the frame rails are level , wouldn't he want to shim the body to level?

Side mount spare

Thank you for the clarification. That's why I asked how the springs where oriented in his model of truck. I have never worked on a Task Force truck. Left side lift block it is.

Good news. I went out and took a look at the U-bolts. They are a good 1" longer from the bottom of the nut.

Mickey, Just a note that once installed and torqued properly, those U-bolts get stretched. For safety sake, get yourself a new set of U-bolts for when you get and install that block. Always best to be safe than sorry.

MikeyP
Shine those 60 year old threads up well & spray down with Kroil for a few days before attempting to remove nuts. If threads are ok, use new nuts to reassemble. If threads are not ok, get new U-bolts.
delky dave in WYO

The threads look excellent. I think the U-bolts may be pretty new.

Thanks to Dan and the others I picked up the shim I need this morning at local machine/welding shop. Charge was $0 but, not to worry, I bought them coffee and donuts.

Good for you Mickey! Thanks for coming back and letting us know you found what you needed.

Shim is installed and it leveled the bed up nicely. Measures floor to top of bed rail 43 1/4" on the right side and 43 1/8" on the left. I'm pleased.

Nice work!

I am wondering how it was determined this was the needed remedy instead of leaf spring replacement, the more common problem? Not knowing otherwise, I would think the weight of the spare tire and mounting hardware alone would be insufficient to cause the listing?

Sparky, The shim in question was originally part of the side mount fender/spare mount tire kit designed by GM to resolve the movement of the spare tire weight from rear center to left side when trucks were ordered with that option. Not an issue of an old or sagging spring, just adding a leveling effect to counter the weight movement. Mickey's truck didn't originally come with the side mount spare fender. Something he switched to in his build and the spacer was the final piece to finishing the relocation puzzle.

My truck has always had a lean that drives me nuts. Never thought it was the spare causing it. This is good information.

Nathan - This shim won't work in the case of the 1951 rear suspension. Our axles are mounted above the spring, where the Task Force truck axles are mounted below the spring. If you added this spacer between axle and spring you would just lower that side even more.

You could add a "lowering block" on the passenger side to try and even out your lean, guessing it won't cause your rear to then be lower than front end, which may not be the effect you are looking for.

Yes, that’s the way I’d do it. Long way down the list if I ever get around to it.