A kit for raising and increasing wheel torque of an off road four wheel vehicle comprising four portal boxes, each portal box being associated with an individual one of the vehicle wheels, the portal boxes enclosing identical gear sets and associated bearings, each portal box being adapted to receive the output of an axle constant velocity joint and having an output shaft projecting therefrom, a set of four metal backing plates for joining the portal boxes to the suspension arms of the vehicle, the backing plates being substantially identical, the backing plates each having inwardly extending mounting brackets for attaching to upper and lower suspension arm parts.