The optional center differential can be installed on Revo 2.5R* or 3.3 to help balance the distribution of power to reduce front end lift on acceleration and improve steering responsiveness. Requires forward-only conversion (included). *Requires short-rear output shaft, part 5416, for use with Revo 2.5R standard chassis. Designed to work in conjunction with the Revo rear brake kit 5417. Rear output shaft is long to accept rear brake kit. Standard length Revo chassis will requires either modification or short output shaft 5416.