It's been several years since I rebuilt mine, but I do believe you need it. If I'm thinking correctly, it sets the pinion bearing in the proper place when you tighten down the three lock bolts in the case of the carrier/torque tube.

Jeff


My 1953 Chevrolet
1947.1 Gallery
1972 C-10 1/2 Ton & 1972 C-30 1 Ton