CJ750 toolbox
A few words about final drive gear ratios from Greg
The 3.89:1 final drive was the original R71 sidecar ratio so it will work on a sidevalve fitted with an appropriate chair (and the BW40 style isn't it). In about 1944, the Soviets swapped from the 3.89 to the 4.625 (from the R5) for improved off-road performance. The original R71 solo ratio was 3.60 and these gear sets are available though very expensive. A 4.11 or 4.22 final drive can sometimes be found through the Russian/Eastern European dealers for a reasonable price and they work well on a sidecar. The 3.89 ratios are available from Ural dealers and are of a good quality. Taking time to mesh the gears properly and shimming correctly is vital for a long life. Most failures are the result of incorrect shimming and not quality issues.