Time is winding down before Abby and Rick’s departure for Seattle via points South and a 4000 mile arc around America. Abby has had a major mechanical makeover, with almost every system renewed to ensure a trouble-free journey.
In this video, I share a bit about rear axle ratios. Rick chose to drop the stock ratio of 4:22 down to 3.9 by using a differential from a later Sprite/ Midget. He’ll sacrifice a tad on acceleration but gain a nice RPM reduction at highway speed.
You’ll find the relevant numbers stamped on top of these differentials. These indicate the number of teeth on the ring and pinion gears in the diff. 4:22 shows 9/38, while 3.9 shows 10/39. The numbers are hard to see when the diff is in the car, but you can try with a mirror, or remove the diff and count the teeth!