How to assemble a differential | Austin-Healey Bugeye Sprite Project

Installing our new limited-slip differential obviously forced us inside our Bugeye Sprite's differential. So, while we weren’t planning on changing much else, when we got inside the diff, we wanted to at least change the pinion shaft seal as this differential had been sitting for who knows how long.

We needed to remove the ring gear to install the limited-slip in the carrier. To make sure it went back as originally placed, we marked the ring gear. We also marked the nut, center shaft and housing with a chisel. 

We also sourced new lock tabs from Moss Motors and torqued the gear to 46 lb.-ft.

We weren’t thrilled with the pinion bearings, however. We ordered all these parts from Moss Motors for less than $50.

Once apart, if you are doing nothing else, you should be able to just tighten the pinion nut to about 135 lb.-ft. and just line your marks back up. While not technically correct, this should get you back within spec.

The pinion shaft wants to be under about 12 lb.-ft of preload, and you crush a sleeve until you get there. Hint: At about $5 each, have a couple of these sleeves on hand as it’s a one-shot proposition. Another hint: You can better measure this with a torque wrench marked in inches and not feet.

The bearing caps need to also be marked left and right and then need to be torqued to 60 lb.-ft.

There are also shims between the carrier bearings and these caps. There are numbers stamped on the carrier bearings that explain what size shims need to go on which side. Every car is different.

A formula for properly shimming these carrier bearings so they best mesh the ring gear with the pinion gear can be found in the shop manual.

Image Courtesy Moss Motors

As our carrier bearings were deemed to be in good shape, we didn’t mess with any of this. Still, we ran some grease on the gears and put the differential through its motions. We could see a proper wear pattern at the center of the gears, so we put the carrier back in the housing after cleaning the differential housing and replacing the seals.  

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