Rear Suspension Info

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With this info I hope to provide a little more insight into Toyota truck and 4Runner rear leaf suspensions and some of the ideas I have found work well for me. Please note that most of the qualities I strive for are for rock-crawling purposes, while still maintaining good on-road manners.

I'm running the original Mazda Spring Swap on my truck. Details about this swap can be found by following links found here. Stock Toyota rear springs (pre ‘89) are about 47 inches long. ('89 and newer springs are about 4 inches longer.) Distance from the center pin hole to the front eye is about 20.5 inches. Using longer, flatter springs can help increase articulation and improve ride quality.

In any case, experience has shown that thinner leaves (~.280" or less) seem to work best for rear spring packs if maximum flex and travel is a goal. Also, load leaves should be removed if you want the spring to flex backwards.

Realize, though, that allowing the springs to flex backwards may shorten their life and/or cause them to kink depending on leaf packs and other suspension factors discussed below.

From opinions I have heard, it seems that Old Man Emu (2.5" lift) and Alcan custom springs seem to be the best liked among those made on the market. Both offer high quality springs with nice, flexy leaf packs. Note that these are typically on the upper end of the price scale as well.

I, personally run a set of Mazda hybrids of my own making. They are relatively soft and flat springs combined with welded steel blocks (shown here). I used rectangular stock and plate to fully box the blocks. These sit 1 1/2" over the stock perches.

Others have used various Jeep Wrangler, Ford Ranger, or full-size Chevy springs to gain various length and rate leaf packs.

Whenever the load leaf is removed or longer, flexier springs are used, some type of traction control must be used to control rear axle wrap. I chose to use a two-link traction bar at the rear axle. I find this type bar provides the best characteristics by controlling axle hop without limiting travel or articulation.

My custom center mounted track bar is shown here. I fabricated a steel boxed mount and welded it to the top of the differential housing.

The track bar attaches to this mount using 1/2" bolts and poly bushings.

A 4 inch long boxed shackle bolts to a steel mount on the horse collar crossmember. Poly bushings are used at this connection. The other end of the shackle attaches to the forward end of the track bar using a rod end (heim joint) to allow for plenty of axle articulation.

For more discussion on various traction bar designs, see the article entitled "Track Bar Tech" in the April 1998 issue of Off-Road Magazine.

When looking for increased travel on the rear suspension, it may be necessary to modify or relocate the shock mounts. There are several methods. One I am currently using is described here.

I chose to fabricate a new upper shock mount that was welded to the round crossmember above the rear axle. The shocks are bolted to this mount using 5/8" bolts that run parallel to the frame rails.

New lower mounts were also built and welded to the axle housing. The studs on these also run parallel to the frame rails. One downside to this particular design is that if a stud does break off a new mount will have to be welded onto the housing. So far, I have had no problems with this setup.

The photos below show some views of how I mounted my rear shocks.

With my longer rear springs and stock width rear axle, I had problems with the tire under compression hitting the frame rail and inhibiting further articulation. To cure this I added a set of custom wheel spacers. The spacers are made from blue-anodized billet aluminum. The 1.25" thick adapters bolt to the axle flanges using stock studs and lug nuts. An additional six studs (stock front studs) are pressed into each adapter and each wheel bolts to the adapter. Ten week old Ethel shows off one of the adapters here.

Thanks for reading!