I'm going to be opening up the axle on my 2WD 22R which has a 4.11 gears and a noisey bearing, to replace bearings and install a set of Richmond 3.90 gears. Some catalogs and online suppliers offer "Differential Install Kits" consisting of bearings, shims, crush sleeve, etc, however the kit offered is different for OEM gears vs Aftermarket gears? Why? What is different about aftermarket gears that they require a different bearing/shim kit? Any light shed on this would be greatly appreciated.

 

Just different manufacturers include different things in their install kits. Actually, the Genuine Gear install kits are some of the best.

WTH are you going from 4.11 to 3.90 though? If you get the RPM's too low, you're actually going to HURT your gas mileage with the 22R...

 

I'm changing the rear end ratio in part to lower RPM, and in part because a while back I replaced the 4 speed gearbox with a 5 speed. The 5 speed gearbox was out of a vehicle with a 3.90 or so rear end, so my speedometer is no longer accurate, reads considerably faster than true road speed.

 

Ohhhh - gotcha.

I would just put on bigger tires. LOL