I have an older tmaxx 2.5 that recently seized up,so we installed a 3.3 exchange motor and aligned gears perfectly so that on a tiny strip of foil passed thru them and made a perfect accordion. Ran 4 tanks thru new motor break in and the fifth tank you can use full power,stripped out spur gear? We did find a small rock that dropped out of that area ,not sure if stock did the damage or what caused it. What is suggested at this point . Metal gear? Just wanted to see what the norm would be and what I can do to make it dependable. Thanks for all and any suggestions