Don't know about axles and diffs, but towing in reverse is the quickest way to smoke a belt.
Actually you should never really pull or tug anything in reverse with any vehicle including atvs, trucks, cars, etc. Reason being is the ring and pinion gears in the differentials. One side of the ring and pinion teeth are cut straight (forward motion) and the other side is cut at an angle (reverse motion.)
Here's a picture showing what I mean. Take a close look at the ring gears teeth in the bottom right of the picture...
Sent from my iPhone using Tapatalk so please excuse my fat finger syndrome.
Not all ring and pinion gears are cut this way. The XMR has spiral cut like this but the regular outlander has straight cut gears.