[Angel And The Wolf]

If I connected the drive shafts of one engine and five speed transmission to the left half-axle of a differential, and a second engine and five speed transmission to the right-half axle of the same differential, how many different ratios can I get at the center drive of the differential, and how would I calculate each?

I would include 1L/1R, !L/2R, 1L/3R, 1L/4R, 1L,5R, 2L/3R, 2L/4R, 2L/5R, 3L/4R, 3L/5R, 4L/5R, and 1L, 2L, 3L, 4L, and 5L, with the Right engine cut off.

I count 16 distinct gear ratios,(more, if I include independent throttle pedals) but I just don't know how to calculate backwards through a differential.