[JaVeRo]

There may be an easier way of checking the ratio.

A 3.42 is a 41:12 ratio (actually 3.4166666...)
A 3.73 is a 41:11 ratio (actually 3.7272727...)

41 turns of the driveshaft will give either 11 turns or 12 turns of the axle.

Jack up one wheel and turn the driveshaft 41 turns. With an open differential the wheel in the air will turn either 22 or 24 times. I'm not sure how it would work with a locker or limited slip, you may have to jack up both wheels and hope they turn together.

James