the gear boxes are interchangeable, however you need to see if you have other problems causing the gear box to fail. its common for the acme thread in the landing gear to wear and fail. Most of these have grease fittings but are never greased. The only way you can tell if the leg is at fault is to place the RV on jack stands or on your truck...
Remove the motor, gear box and cross shaft. Drive each leg with a drill motor, up and down... if during the leg up and down through the stroke of the leg, you find that the drill motor loads up during that process the acme thread and nut inside the leg is bad.... thus adding excessive load to the gear box and motor..
You might also see this when you raise and lower the RV with the landing gear, where you hear the motor load up excessively...
Hope this helps..
Retired Business Owner, Re-manufacturing HD Clutches, Brake Shoes, Air Compressors, Sales & Installation of PacBrake and other Industrial Friction