A number of Bugeye owners have suggested switching the original 4.22 rear differential for a 3.9 differential from a later Sprite or Midget. We located a 3.9 in North Carolina. We had it checked out by Glenn’s MG in St. Petersburg. He installed a new pinion oil seal and set the pinion pre-load to factory specification. We cleaned up the pumpkin and painted it with silver caliper paint from POR-15.
The Episode Eight video provides details on the 3.9 differential installation and background.