Rosenbauer offer a 6X6 Sprinter fire appliance chassis with light pump or light rescue bodywork, and there may be others too. These are not very common, and are mainly bought for use in mountainous areas of Germany, Austria, Switzerland and northern Italy, where winter weather road conditions require AWD. They are not really designed nor intended for serious off road work, and the third axle conversion idea is to both improve traction and also increase payload, as the 4X4 Sprinter maxes out at 5 tons. This means that by the time you have added a crew cab, bodywork, a pump, equipment and such, the tank capacity cannot much exceed 500 to 600 litres. The idea is not unlike the old Land Rover and Range Rover fire appliance tandem axle conversions, but these are even less successful.
Added by on 16 March 2022.