Solid Front Axle Swap

Oct. 01, 2005 By Chris Geiger
Toyota Tech

Solid Front Axle Swap
IFS to  Solid Axle 

As I tackle more difficult rock trails I have been having more and more problems with the IFS suspension the factory saw fit to put on my truck. Over the past two years I have broken 2 front axle CV joints and have damaged or bent 5 idler arms.  It seemed that every time I took the truck out on the trail my alignment would be knocked out. I also wanted much more front wheel travel. I was able to take the truck through the Rubicon twice with the IFS but with more travel  and strength I could take the more difficult routes. I often found that I needed to find the easiest way through a given section. I don't want to take the easy way anymore! I want more reliability, articulation, and strength. I looked at several other options including WCOR's 14" mega travel system and Downey's mega travel kit. While giving 11"-14" of travel  these and other similar kits utilize the stock 7.5 " diff,  original outer CV joints, and  idler arm. These parts need to be replaced to gain any real improvement in reliability. 

Before the swap my truck ramped 657 (forward with full tire pressure)  and had only 6" of front articulation.  Now it easily scores over 1,000 on a standard 20 degree ramp and has 20" of front articulation.

I chose to use the front axle from a 1985 truck and to use a "basically Toyota way" of mounting it. The ''84-''85 housing assembly is a little stronger then earlier units as it is reinforced on the bottom.  I wanted to do the swap with tested and proven components.  I did not want something to take months of experimenting and tweaking to get right. Many people have already done this swap so it's not new or even radical. This design has been worked out, and is very similar to how Toyota built trucks prior to 1986. A few improvements were made including: 

  • Crossover steering
  • Lifted springs
  • Drop front mount spacer blocks
  • Moving the axle forward 1"
  • U-bolt flip kit
  • Long travel Rancho 9012 shocks.
  • Vented rotors with larger V6 calipers
  • Heavy duty tie rod
  • Heavy duty axles
  • I obtained a complete '85 axle in good condition from Marlin Crawler. He also set up new Precision Gears into a V6 rear third member for the axle. This is the same third member I have in the rear of my truck. It is much stronger than the 4cyl 3rd member that was originally in this axle. A locker that fits into this V6 diff is same as the model used for the high pinion FJ-80 diff (future upgrade?). A 4Cyl truck uses a different model locker than the V6. My front  diff is open for now but will be getting a locker soon. The axle came in pieces and needed to be assembled.

    When installing the front axle shafts I welded a small button on the diff end of each axle. This allows for the elimination of the bothersome C-clip that holds the Birfield to the inner axle. This C-clip makes it very hard to separate the axle from the joint on the trail. The small weld prevents the axle from sliding out of the Birfield and into the differential. Now the axle can easily be separated from the joint and removed for service. 
    For the front tie rod I wanted something much stronger than stock. I have seen too many broken tie rods on the trail and did not want to have to worry about hitting it with rocks.  With the IFS, the front skid plate protected the tie rod from damage but on the solid axle it's right out in front. I installed a "Marlink" heavy duty tie rod. This unit uses FJ-80 Land Cruiser rod ends and has 23mm threads, larger and stronger than the factory 21mm rod ends that the factory uses.

    With my rebuilt and "Marlinized" axle I was ready to see the folks at All Pro Off Road in Hemet, CA for the axle swap. I scheduled 4 days for the swap and made sure there was a rental car company in town in case we ran into trouble. I had to be back in Santa Barbara by Sunday night. I could not find anyone to help me get the axle into the truck so I ended up using my high lift jack, a floor jack and a come-along to get the axle into the truck. I wish I had a picture of that!

    The swap - day one

     I arrived at All Pro at 11:00 am on a Wednesday. The first thing we did was ramp test the truck. It ramped 657 forward with tires at 35 psi. Pete and Charlie immediately removed the IFS arms, diff, shocks, etc. These guys are fast workers. By lunch time the entire IFS was disassembled and laying on the ground.  After Lunch Pete cut off the IFS brackets and Charlie ground down the old IFS bracket welds on the frame. Pete took the hubs that I had removed from the '85 donor axle and removed the rotors. He installed new longer and larger studs. The original brake calipers on this axle were a bit small. In order to keep the calipers from my truck it was necessary to replace the front rotors with Land Cruiser rotors. These rotors fit on the axle and had the wide vented design that allows the V6 style calipers to fit.


    A tiny bit of grinding on the backing plate was all that was necessary to get the V6 calipers on after that. The primary reason for using these rotors was for breaking but there is a second advantage:  width.

    In 1986, Toyota switched to a 3" wider rear axle and IFS. The rear axle on my 4Runner was 3" wider than the '85 rear axle, the front is a little wider but not the as wide as the rear. All Pro install their 1.5" spacer kit on the front axle. This kit contains (2) 3/4" spacers and new longer and larger lugs and nuts. With the spacer kit on the front the axle is now only 3/4" narrower than the rear. Looking from the back of the truck you can't see the difference. I had to measure it to discover the difference.

    So at 5:00 p.m. all work stopped and everyone went home. I was amazed how much work had gotten done in just 6 hours and that included a full hour for lunch! The truck sat in the garage with no front suspension at all, it's new axle sitting just a few feet away. I did not sleep well that night - will it work right? Will there be any problems? How will it ride? How much flex will it have? 

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