Originally Posted by PorTX

I went up to 5K....so the rear end would not be so "loose". The shims will help the mesh of the conical and bevel gears. It will help cut down on the side to side play of the diffs in the housing. If you bought a new ECO in the box, there will be a few shims in one of the bags. I ended up using 2 on each the front and rear diffs. You will install them on the side that pushes the conical gear closer to the bevel gear.