ProRock Solid axle swap (sas) ...

Its been eleven years since we completed the very first in the US and very successful solid axle swap (sas) in May of 2001 on my then new 1997 Montero Sport LS 5-speed. Since the build I've needed to make a couple minor changes to the original design - reinforceing frame rails, relocating the steering stabilizer, changing rear spring rates and changing from Napa stock disks and pads to Power Slot disks and Hawk Performance pads but otherwise it survives unchanged since 2001.

Over the last few years I've spent more and more time four wheeling in southern Utah on progressivly more difficult trails and my vehicle performance needs have changed. I need something that's more rock crawler than street vehicle. So, rather than a 70/30 highway/off road mix, a configuration that's a little closer to 30/70 highway/off road.

I still use my current SAS'd Sport for work and playing in Colorado and I want to continue to do so. Rather than redesign my existing Sport I chose to start from scratch with a new vehicle. Within a couple weeks of deciding to start a new project the sister to my orignal '97 showed up in the parking lot of my office building and was coincidentally for sale. This Montero Sport is the same year and model as my current SAS'd Sport with all of the same options except the leather interior and heated front seats. The vehicle was what I was looking for and too good a buy to pass up so I purchased it a week later.

My primary reason for purchasing this particular model of Montero Sport was to leverage the engineering effort that went into the solid axle swap on my first '97 Sport - to cut engineering and fabrication costs throughout the new design and build. Only slighly less important was my requirement to not create difficult and expensive obstacles to overcome by involving such things as ABS and transmission computers commonly found on 1998 and newer Montero Sports. I also planned to continue using leaf springs in the rear of the new build so starting with a leaf sprung Sport would be more cost efficient.

Finding and purchasing a new project vehicle is only the beginning. The next step is restoring the vehicle to a completely functional state. That means repairing anything that's broke, getting maintenance up to date, and fixing anything that was broke or done incorrectly by others doing 'repairs' and 'maintenance'. As usual, the Quality Mitsubishi service and parts personel have been invaluable in preparing the vehicle for the solid axle swap.

There are some modifications that are easier to do while the vehicle is still unmodified and on a stock suspension. It's a lot easier to work on the interior or in the engine bay, for instance, when you don't need a step ladder. Keyless alarm system, leather interior to replace the factory cloth upholstery, ARB Bull Bar, rock sliders, headlight harness and AGM battery top off the list. It's taken five months to complete all the repairs, general maintenance and modifications but it's time well spent. There's no point in doing a major modification like an axle swap to a vehicle that doesn't run.

With all the preliminaries taken care of it's time to start on design and what parts to use. Currie's unwillingness to sell me a pair of Dana 44 axles was something of a shock since that's what I use now but there are other companies who build and sell axles so I went shoping. After a couple months of shopping around and mulling this over in my head I finally settled on Dynatrac ProRock axles. While speaking with Dynatrac the decision was made to go with the ProRock60 (Dana 60) rear axle rather than a Dana 44 as I'd used in my previous build. The drawbacks to using a Dana 60 rather than a Dana 44 are still the extra 120 lbs. or so of extra weight and the increased parasitic power loss, but I'm only using a Dana 60 in the rear and the vehicle won't be used as a daily driver. The pricing difference between a ProRock60 and a Dana 44 built up to the specs of my Currie Dana 44 is only a couple hundred dollars - not enough to quibble over when you're talking about $5000 axle assemblies. Matching the ProRock60 in the rear will be a ProRock44 in the front with 1/2" wall tubes. Both axles will be fitted with 5.38 gears and ARB Air Lockers.

Front suspension

Rear suspension


Drive train

Materials and parts ...

  • 1997 Mitsubishi Montero Sport LS
    • 3.0L 6G72 V6
    • V5MT1-6 5-Speed transmission
    • Off road package, skid plates, gauge pod, rear swing-out tire carrier
    • Limited-slip rear differential
    • Tan/brown cloth interior
    • Six speaker stereo w/remote 10 CD changer
  • Dynatrac JK ProRock60 Axle
    • 5.38 gears
    • ARB differential locker
  • Dynatrac JK ProRock44 Axle
    • 5.38 gears
    • ARB differential locker
    • 1/2" wall tubes
  • Late '70s GM front disk brakes
    • Power Slot Cryo Brake Rotors
    • Hawk Performance Brake Pads
  • Late '90s Ford Explorer rear disk brakes
    • Power Slot Cryo Brake Rotors
    • Hawk Performance Brake Pads
  • Mitsubishi heavy duty steering shaft and joints