Something I copied from the LCML years ago:
All or most FJ-40's lean to the left a bit. Toyota has a bulletin about it. "Toyota Service Bulletin; Volume 5; Reference, Body; Number 10; November 14, 1976; Model FJ; Title, Body Slant" is the bulletin. It says to measure and find the "high corner"
(right rear, generally) and to install the listed Toyota Factory Slant Correction Plate. Yes, there is (or was...) such a beast. The part number is 48475-60010 and the caption for it reads: "Plate, Spacer". You will also need two longer U-bolts, part number 90118-14107, that are 175mm (or 6 7/8") long. Job time is rated at eight-tenths (8/10) of an hour and is reimbursible within the provisions of the Warranty Manual for dealers (Not that the warranty matters anymore...). Basically, you pull the u-bolts on the right rear, slip the spacer plate between the spring and the axle, install the new, longer u-bolts and tighten to stock spec. How does it work, you may ask?
Well, it isn't all that thick, but the length is key. Tightening a flat plate against the leaf will flatten or pre-load it a bit and lower that corner, leveling the vehicle. Leaving the plate out won't hurt anything, but I think putting it in may limit suspension travel and may harshen up the ride a tad. So, if you are restoring a truck for on-road use, it may be worthwile so you don't have a truck that leans. If you are planning to off-road, don't worry about it. As for why it leans in the first place, there are a number of theories. The one that sounds most logical is that the frame/suspension were originally designed for a right-hand drive truck, with the driver, gas tank and spare all on the right, and the engine was offset a bit to the left. So, on a left-hander, moving the driver over screwed up the weight balance a bit and it leans a bit after the springs wear in some. Mine leans. It also squats in back, but that's just the 171K+ miles and the crappy re-arch showing up...
