TM 9-2320-361-10 1-21. SHOP VAN TRUCK, WO/W AND W/W: M109A3 a. Purpose of the Vehicle. The M109A3 shop van truck is used as a mobile repair shop. It is also used to transport special equipment that must be kept free of dirt, dust, and moisture. b. Special Limitations. The height of the M109A3 shop van truck is not reducible. SHOP VAN TRUCK (M109A3) 1-22. INSTRUMENT REPAIR SHOP TRUCK, WO/W AND W/W: M185A3 a. Purpose of the Vehicle. The M185A3 instrument repair shop truck has the same basic purpose as the M109A3 shop van truck, except that special equipment included with the vehicle make it more suitable for extensive field repairs. b. Special Limitations. The height of the M185A3 instrument repair shop truck is not reducible. INSTRUMENT REPAIR SHOP TRUCK (M185A3) 1-10