Erik's 4Runner- Rear Axle and Suspension

Rear Springs - Rear Axle

Tacoma Rear Axle- under construction, more info to come. In the mean time, click here for the pics and info: Trussed and shaved axle housing

Material: bottom of diff plated with 1/4" steel, truss was cut from a 2' chunk of 2x6" .120" wall, spring perches are 2.5x2.5" .188" wall, blocks are 1.5x2.5" by .188" wall.

Housing bottom was cut out with a grinder and cutoff wheel. Plated bottom leaves just 1/8" of clearance to ring gear and bearing caps. Increase in ground clearance of about an inch, plus smooth bottom slides over rocks more easily. Fill plug was moved to top of housing. Draining is done by removing two lower diff bolts.

U-bolt plates are 1/2" thick, based on this plate pattern, with 5/8" u-bolts.

E-brake cable extension is just two strips of steel with holes, bent to fit, and a bolt.

"8.4" Tacoma/T100/Tundra rear diff with ARB.

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DSC00966.jpg (62331 bytes) ebrake_cable.JPG (62092 bytes)    


Chevy spring swap- somewhat old info, will be updated soon...

Comparison of stock and Chevy springs

Spring hanger
11" forward

Shackle hanger
4" back

Springs installed w/ 2" blocks and shims.







My other hangers:

Edge's truck




Old jeep hanger
DSC00438.JPG (61879 bytes)

New low-profile hanger
DSC01773.JPG (332186 bytes)
DSC01757.JPG (329576 bytes)

DSC01761.JPG (326740 bytes)

Also check out the Chevy swap I did on my buddys truck using low-profile front hangers and the double shackle setup:

And don't forget the BBS  Chevy Spring Swap FAQ as well.


New- now I've made some even lower-profile hangers when I put Chevy's on my T100:
T100 Chevy hangers 

Also made some new ones for the 4Runner as well (see bottom of page)


I wanted more rear wheel travel and a softer ride for minimal cost. I did a little research on the net about the different common spring swaps done on Toyota's and came to the conclusion that the Chevy 1/2-ton spring swap would be the best for me- "lotsa travel and they ride like a Cadillac". One big deciding factor was that for the Mazda and S-10 spring swaps, a track bar was required to keep from kinking the very soft springs. With the Chevy 1/2-ton springs, a track bar isn't necessary.

'88-98 Chevy/GMC 1/2-ton springs are over 63" long.  They come in 3 or 4-leaf packs (plus overload) and have a centered pin. I used the 3-leaf pack.  For comparison, my stock springs are 48" long with an offset center-pin- the front half is 20.5" and the rear half is 27.5".

To mount these loooong springs to my 4Runner I bought Jeep CJ spring hangers and welded them to the flat part of my frame 11" forward of the stock spring hanger (hole-center to hole-center).  I had to remove the gas tank so that we could weld the inside of the passenger's side spring hanger. For the shackle hanger, I found some used stock shackle hangers and welded them on right behind the stock hanger, which is about 4" back from stock.  I chose to leave the original spring and shackle hangers in place, so I had to cut off the front spring clamps and bend the spring hanger outwards to keep the spring from hitting it. I re-used the stock U-bolts and had to grind a bit off the sides of the springs to get them to fit since they are slightly wider than Toyota springs. I also had to bend one end of the shackle out a bit wider to get it to fit the spring. The emergency brake cable ran right on top of the springs in this configuration. It rubbed a little, but not too badly.  This hanger position moved my axle back just slightly and I ended up with the tire very well centered in the wheel well as planned.  Using the 3" longer than stock shackles that I already had and removing the Chevy overload leaf, this setup gave me about 3" of lift and a nice, steep shackle angle.  I'm also using a 4 degree shim to point the pinion flange directly at the transfer case because I have a CV driveshaft and for better ground clearance.

I wanted more lift than 3", so I installed some Trailmaster 2" blocks and ran the E-brake cable under the springs.  This was a little better, but the springs are very soft and when loaded down with all my junk for the trail (spares, tools, and food and camping gear for 3-5 people), I felt I needed more.  Next I put in some Rancho add-a-leafs and put the stock overload leaf (7/8" thick) back in upside down. With no load, I've now got about 7+ inches of rear lift, but loaded down for the trail, it settles down to about 4", which is about what I want. It has a bit of "rake" when unloaded, but either it doesn't look too bad, or I'm used to it.  The Rancho add-a-leaf kit actually replaces the stock middle leaf with the add-a-leaf, so it doesn't add much (if any) to the spring rate, and I'm still able to stuff the tires in the wheel wells with no problem, even without a load in the back.

For shocks, I'm using Rancho RS5005's (29.48" extended, 17.22" compressed) in the stock mounting location. These springs easily use up all of the 12+ inches of shock travel. I measured about 18-20 inches of wheel travel when I first took it out.

All I can say about these springs is THEY WORK GREAT!!!! There is such a huge difference between these and stock springs that it's incredible.  Both the on- and off-road ride is softened and improved.  Off-road they work very well to keep the tires on the ground to maintain traction.  Even with open diffs, these springs enable me to go many places that I had a really tough time with before or even couldn't make. People watching me drive sometimes find it hard to believe that I don't have lockers. I've run Fordyce and Rubicon each at least twice this summer, as well as quite a few other places, and I'm still VERY happy with these springs and they are holding up well. For the price, I think this is probably the best setup out there. The only thing I would do differently would be to make my own spring hangers instead of using the Jeep hangers since they hang down too low. I made some hangers out of 3.5" x 3.5" x 1/4" tube for my buddy's swap that mount the spring about 1" closer to the frame and I made them long angled them so that they can "ramp" over rocks if necessary. Someday I may go back and make some of these for myself.

In the middle of this swap found out that there is a cheaper and easier way to do the rear of the springs and even get more travel.  If you use the Toyota style shackle in conjunction with the stock Chevy shackle you don't have to weld in a new hanger.  Mount the Toyota shackle in the frame hanger and let it lay flat against the frame, and then mount the Chevy shackle between the Toy shackle and the spring. This dual shackle setup bolts right on and gives you a bunch of extra suspension droop. Of course, your shocks have to be long enough to take advantage of it.

Original project costs:
'92 GMC 1/2-ton springs (Cordova Truck Dismantlers)- $75
Jeep CJ spring hangers and bolts (Foothill Offroad)- $45
Used shackle hangers- $10
Welding (a big thank you to David Fritzsche!)- ~$20
Total =  $150 and you could probably do it for a lot less if you made your own spring hangers, used the double shackle method, and did the welding yourself.

Later costs:
Trailmaster 2" blocks (Central 4 Wheel Drive)- $60?
Rancho add-a-leaf kit (Central 4 Wheel Drive)- $100
New longer U-bolts (Dentoni's Custom Spring)- $36

I like what I have now, but who wouldn't want more travel?  In the future I plan on cutting off the shackle hangers and mounting a buggy leaf (this is also called 3/4 elliptic).  I'll also need to change how the shocks are mounted and install longer shocks to take advantage of all the available suspension travel.

Update: (1/01)
I cut off the second set of shackle hangers to use them on my straight axle swap and installed Chevy shackles ($10) in the original shackle hangers connected to the Toyota shackles.  It didn't change the lift or shackle angle much and for now I don't get any extra droop since my shocks are the limiting factor as well as driveshaft and brakeline limitations.

Update: (3/03)
I cut off the Jeep hangers on the 4runner and replaced them with the ones labeled "New low-profile hanger" at left (basically the same as the T100 hangers). They hang down a full 1" less than the old ones and are ramped and plated to slide over rocks much better. They look good and work great so far. I haven't hung up on them yet like I did on the old ones.


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