POWERTRAX - GRIP PRO POSI LIMITED-SLIP DIFFERENTIAL - The POWERTRAX Grip Pro is the latest design in traction adding differential technology. It combines the smooth operation of a limited-slip differential, with the strength of a fully machined, forged steel case. Using 3x2 spiral gear technology, the POWERTRAX Grip Pro delivers progressive and variable traction. Based off of throttle input, you are in control of how much traction is applied. Great for use where finesse is as important as brutal traction is. On the road, in rain & snow, and on the track, Grip Pro is a winner! The POWERTRAX Grip Pro comes fully assembled. Because there are no friction plates, so you can use any gear oil you like, including full synthetic and racing lube. And don't forget that there is no friction modifier additive necessary! - COMPATIBLE WITH DODGE/CHRYSLER 8.25 inch W/ 29 SPLINE AXLES