Project RangeRunner has undergone quite a transformation over the past several months, and with suspension and power out of the way, it was time for us to start looking at traction options. With the high-speed nature of Project RangeRunner, we didn't want to install an automatic locker because of the quirky handling characteristics at the limit, but we still needed a differential that would work well on our drive to work, or the occasional rockcrawling section. In stock form, our Ranger came with a preloaded Torsen T2 in the rear axle, which worked amazingly well on the street, on the slow stuff, and on fast dirt roads. We were so impressed with how this unit operated, that we decided to give the folks at Torsen a call and see if there were any tricks up their sleeve to improve the performance of Project RangeRunner.
Here, our new Torsen limited-slips are waiting to be installed.
We were ecstatic to find out that a Ranger race-truck program had recently been retired, and from it, a modified T2R was available for our rear 31-spline 8.8-inch axle, so an upgrade was in order. We also found out that this program included a prototype front Torsen T-2 (non-preloaded) for our hybrid Dana 35 front differential, of which only a handful exist and only two are in use. When Torsen offered this piece up for our project, they wanted to see if there was a market for the SLA Ranger enthusiast, so we jumped on the chance to try it out in our truck and test the waters for them, through our readership--especially knowing there is only one other traction device that physically works in the Ranger's front Dana 35 housing, but it wasn't made for SLA Rangers, and can cause problems down the line.
Torsen differentials are torque-biasing limited slips, which use parallel-axis helical gears, instead of clutches to build friction internally, which ultimately prevents slip and provides traction. The benefit of the helical gearing setup is that the performance of the differential will stay the same over the lifetime of the unit, while clutch-type differentials can wear out and become ineffective over time. These limited slips are always active and transfer the majority of torque available to the axle, to the wheel with most traction, proactively preventing slip. Under low loads, they differentiate readily, allowing low-speed maneuverability that is superior to a locker.
Our prototype diffs have a higher Torque Bias Ratio (TBR) than either a standard Torsen differential, or the Torsen found in the FX4 Level 2, which means that we are getting extra torque to the wheel that has traction. Our front Torsen has a TBR of 2.4:1, and our rear Torsen has a TBR of about 4.0:1. This means that up to 70 percent of the available torque to the front axle and about 80 percent of the torque available to the rear axle can be transferred to the respective wheel with the most traction.
We took our Ranger to our friends at Off Road Unlimited's Victory Blvd. store in Burbank, California, where our Torsen diffs were expertly installed. The following is a quick overview of the installation:
1. We began the install by draining the rear differential and removing the cover. | 
2. Since we were not changing our gears, we had to use a dial indicator to measure where the ring-and-pinion were at so that they could be reinstalled properly and within their already established wear pattern. |
3. Next, the C-clips and axles were removed. | 
4. Before the ring gear could be pulled, the bearing caps had to be removed. |
5. With the ring-gear assembly out of the differential housing, the ring gear and toner ring are reinstalled on to the new diff. | 
6. Once we were satisfied with the contact pattern on the gears, the diff cover was ready to be sealed and the housing refilled with gear lube. |
7. We then removed the front diff housing from the truck and drained it. | 
8. Here you can see the stock open front differential, compared with the Torsen we installed. |
9. After finding worn bearings and a lot of metal in the front diff, it was important to make sure we were starting with a clean housing (and new bearings) before continuing with the install. | 
10. After separating the stock diff from the ring gear, we reinstalled it on the Torsen diff. |
11. Just like the rear, the front was measured and checked for an acceptable contact pattern before being buttoned up. | 
12. With the cover in place, it was time to reinstall the front differential housing and start enjoying our newfound traction. |
How It Works...
After several hundred miles on various off-pavement terrains, we can't believe how well the front and rear Torsen setup works. On fast dirt roads, the supercharger can be used to power the truck through the turns, predictably and confidently. There is no understeer, and we can four-wheel drift around tight corners with a stab of the go-pedal. In the rocks of the Mojave Desert, Moab, and Death Valley, the differentials have given us all the traction we have needed, and not once have we wished we had gone locked-up on this truck. For a vehicle that spends a lot of time on the street, the limited slip is the preferable option and we couldn't be happier with our choice. The Torsen differentials have been a big piece of the puzzle in proving the theory behind Project RangeRunner, showing that long-travel four-wheel drive isn't just for fast terrain, but can work equally well in all types of terrain. We would recommend that any Ranger owner who is interested in this setup contact Torsen and let them know there is a market, especially for their front differential.