Well it's not really a mod it's a direct fit you remove your slipper clutch and spur gear and just slide on the rift gear and then you have to modify the transmission case the motor mounting holes need to be elongated by at least a quarter inch to fit and 11-14t pinion... The gear teeth are ginormous, this is made for really an 1/8 scale vehicle so I think the transmission gears would strip before the spur gear and pinion gear would... This is for those trying to get a top speed or durability and dirt or you've already gotten brushless I literally tried every gear option on the market and strip them all out this is the only one that repeatedly takes all of my abuse... I haven't been to shaft either or work the case... So happy bashing.. 
