I have never replaced mine? That is the spurshaft/transfer gear. That is a 14T I believe. The duratrax 14T should work for replacement if looking for a cheaper alternative. Its not right that you need to replace that gear at all. I would check that all the screws in the rear axle mount, alloy gear support plate and motor mounts are tight. The two bolts on the side of the motor that connect the side plates to the motor should be enough to hold the motor from falling forward but, it can happen that the motor keeps slipping forward without the alloy motor mount upgrades. Its just real hard to keep those dang screws tight in the plastic ones. Did you replace the diff gear when you replaced the spurshaft/tranfer gear? Maybe the big diff gear is wearing the spurshaft/transfer gear? If not maybe it just was not meshed right. Take a business card and put it between the gears, pull the motor toward the diff and squish the card between the two. Make sure the gears are as flat against each other and not running sideways. Tighten the motor mounts and mark the motor mount spot on the chassis with a scratch to make sure if it moves you can easily see it has happened.