With new gears and new clutches, the Posi case is difficult—but not impossible—to turn using a spanner wrench on the ring-gear boltholes. Tom recommends rotating the case 50 turns in each direction to wear in the new components. If the case turns easily, a thicker shim package is required. Our case turned easily, so we increased the thickness by 0.005 inch on each side to 0.055-inch shims and eventually to a 0.060-inch total shim package. A second Posi rebuilt this way (with used plates and gears) required 0.070-inch shims on both sides.