No-Slip rear differential in a 1998 Jeep TJ with a Dana 35-C.

After approximately 2 years with my Jeep with the Trak-Lock rear differential, I decided it was time to upgrade to a locker. Being rather new to four wheeling I was hesitant to drastically change my jeeps stock set up too much. After reading quite a few articles and a little on-line research I settled on the Powertrax No-Slip insertable rear differential. From my research, it appeared that this locker offered the best performance with the best street manners. The on-street performance was very important, as my jeep is a daily driver. Cost was another big factor. ARB offers the best of both worlds; a locker and an open differential, but cost, both for the parts and installation, ruled the ARB out. The Powertrax is designed for do it yourself installation.

I ordered the Powertrax and it was delivered ready to go. The parts are easy to identify and there aren’t a lot of them, 20 all together. The instructions seemed fairly clear and the toll free technical support number was reassuring. I am a fair mechanic and felt the installation would be fairly easy even though this was my first attempt at any kind of rear differential work.

I started following the instructions: I blocked the wheels and raised my jeep on to jack stands. I removed the differential cover bolts and drained the fluid. So far so good I thought. Next step, remove the pinion shaft retaining bolt and remove the pinion shaft. First call to technical support. The pinion shaft bolt had a 12-point head instead of a 6-point head. I had never seen a 12-point bolt head before. Technical support explained what I was looking at and even gave me the size of the box end wrench to use. They were off on the size by 1/8of an inch but solved my dilemma for me.

Next, after the pinion shaft is removed, is to push the axles in to disengage the axle shaft “c” clips. This of course requires that the brake drums be removed to access the axle flanges. Well, my drums had not been off since the jeep was built and didn’t really want to come off now. After a little banging, clanking, prying and gentle encouragement, the drums came off, the axles pushed in and c-clips disengaged.

Now the side gears and spider gears can be removed. Second call to technical support. The thrust washers and clutches for the Trak-Lock differential kept the side gears pressed into the differential case against the spider gears preventing their easy removal. Technical support was not as helpful this time. They stated the gears should just come out, and if they did not, to try prying on the gears to get them out. I got an aluminum drift and a 3 pound hammer and encouraged the spider gears to rotate around the differential case until they aligned with the case openings and came out. Once the spider gears were out, the side gears came out very easily.

With all the parts removed, I cleaned the differential housing and case and prepared to install the new parts. The instructions of the various parts made it easy to identify what went where. The coupler is installed on the ring gear side of the case followed by a synchro-gear and a spacer. The ring gear side axle is pushed back in place and the parts are then held in place with the c-clip. The driver is then inserted and the remaining coupler, synchro-gear and spacer are inserted on the non-ring gear side. With all the drive parts in, the springs need to be wedged into their openings between the two sides. Powertrax includes a metal block to determine if the parts and springs have been installed correctly. If all has gone well, the remaining axle is pushed back in and secured with a c-clip and the pinion shaft is reinserted and secured with the retaining bolt.

Powertrax includes instructions on how to test that the differential is performing correctly by blocking a rotating the tires before re-sealing the differential. If all works correctly, the rear cover can be installed and lubricant added. The rear drums can go back on and then the rear wheels. Ready for a test drive.

My overall impression of the installation was that it was pretty easy. Most of my problems were just getting to the point where I could actually install the new parts.

How has the improved rear differential worked so far? Well off road it is great. I can’t spin the rear tires with out concerted effort. I no longer worry about over powering the Trak-Lock or burning it out by slipping a tire too long. On road manners are pretty good too. I can easily chirp my tires going around corners. I can feel a transfer of power between the left and right sides when I left off the gas, especially at higher speeds, which is not too bad. The driveline backlash is definitely more pronounced and it takes more effort to drive the jeep smoothly. Driving in the rain is a little more interesting as well. The jeep just seems a little more “squirrelly” due to the power transfer between the sides. Would I recommend Powertrax? Yes, I think so. The changes in the on road performance are minor and the off road performance is definitely improved. Installation is straight forward and pretty easy and the off road benefits are definitely worth it. Obstacles that took a little speed and momentum to over come can now be gracefully crawled over.