Project SportRunner - Eaton TrueTrac LSD

From the factory my rear differential was open, meaning only one wheel got power when throttle was applied. I began looking into traction aid devices to alleviate that issue. I had a Lockrite automatic locker in a 1997 Tacoma 4x4 that I owned and hated it. The Lockrite was noisy, clunky, and often made the rear of the truck feel strange under acceleration. I also had the TRD electric locker in a 1999 TRD Tacoma 4x4 that I owned. I liked this locker much better than the Lockrite, but you couldn't really use it on the road at all, and I had to modify it to work in anything other than 4WD Lo. Electric lockers are also pretty expensive to put in if they didn't come on the vehicle from the factory. After looking at the available options for Project SportRunner, I decided to give the Eaton TrueTrac a try as I had seen very positive reviews.

Proper TrueTrac for your application (913A610 for 2002 4Runner V6)
3 quarts of rear differential fluid - I like Mobil 1 75W 90 Synthetic
A good shop or proper differential setup tools such as dial caliper, torque wrench, seals, etc

There was quite a bit of confusion as to what size the rear differential was in my 2002 4Runner. After a call to Toyota Corporate and a couple of call transfers I was put in touch with a very helpful young lady who looked up my vehicle's specs by VIN. She told me I had the 8" V6 rear differential which meant I needed Eaton Part Number 913A610. This is the latest part number as of the time of this writing which is a newer more beefy unit.

There are a few benefits of the TrueTrac LSD. One is silent operation. I've not heard it once since it was installed. There are no clutches to wear out as with other LSD units as it is gear driven. There are no special additives required for the diff fluid.

Installation is pretty involved as the unit replaces the stock carrier and spider gear assembly, meaning the gears will have to be set up using a dial caliper and you wanna be sure it's right or kiss your rear end bye bye. If you're fairly mechanically inclined and have the proper caliper, torque wrenches, and time you can probably do this yourself, but I decided to have the local 4WheelParts Performance Center install mine. I must say they did an EXCELLENT job. These guys were the most meticulous technicians I think I've ever come across. When I picked the vehicle up they provided a check list with my receipt which showed the torque values of each bolt down and the technician's number that torqued them. When I got home I double checked the fluid to be sure the proper amount was added, which was on the money, and noticed that each bolt they removed had yellow paint on it showing it had been verified. That's impressive. They wouldn't allow me to photograph the install, but offered to take pictures for me, so thanks to 4WheelParts Performance Center in Nashville, TN for the images in this article. They took 20 different photographs for me and I only asked for 4!

Here's a shot of the stock differential removed from the vehicle as well as one with the TrueTrac installed and getting setup to the proper backlash.

I'm very happy with the TrueTrac unit thus far. I've had it installed for about 200 miles as of July 17, 2007 at 66,670 on the clock. There is absolutely zero noise at any speed, nor can I feel any difference in the way the vehicle drives under normal conditions, even tight 360 degree turns. To test the unit I put one rear wheel on gravel and the other on dry pavement and got almost zero wheel spin when I mashed the throttle. The only thing to be aware of with any of these types of units is their tendency to cause the rear of the vehicle to "walk" or drift to one side in the event both wheels spin. It's not a big deal, just something to be aware of until you're used to it. I'll post a follow up when I have more miles on the unit, but this seems like a GREAT product and will really help with getting that Supercharger power to the ground.