[jkstill]

If you are assembling a new gearset, the pinion spacer may be the incorrect size. This spacer is used to set the depth of the pinion so that the gears mesh toward the middle of the ring gear, between the heel and the toe of the tooth.

The FSM shows how to use some special tools to measure the spacing and determine if it correct. If you have a way to do that without those tools, please post it. Lacking the tools (I didn't try to order them) I opted to use the spacer that was on the stock pinion.

Actually, what really happened was this: I could not remove the rear pinion bearing, and made an attempt to order the same size spacer. The attempt was rather lame, as after the diff was assembled, the pinion was too deep. That's when I made a trip to the machine shop to remove the rear bearing from the pinion, so I could retrieve the spacer. As it turned out the stock spacer was 3.20mm, while the one I had ordered was 3.35mm. Just enough to screw it up.

Once the rear bearing was removed at the shop, I found that the stock pinion spacer worked fine, so no need to order more. Of course without the special Mazda tools, you won't know if the spacer is correct until you have assembled everything, set the backlash and checked the gear pattern.

The rear pinion bushing was pressed on using a 6" piece of 1.25" galvanized pipe from Home Depot.

The rear bearing was then pressed on using a 6" piece of 1.5" pipe. You can see this in the attached pics.

Once the bearing is on it is time to install the pinion and set the preload.

Next: Pinion Preload