So I bought my Big Rock used.... a couple months ago, and had run it a handful of times. I always felt like the drive train was really noisy, but had no other big Arrma to measure against. As time went by, it got more and more noisy, so I decided to tear it apart tonight and investigate further. Serviced the diff, and it was turning smooth, no missing teeth, all the gears still had sharp edges, but the silicone was gross. Black, and gelatinous. So that wasn't the issue. So I checked the mesh, and it felt right, but something just wasn't right. So I pulled the motor mount apart, and upon closer inspection, it had an aftermarket pinion with one set screw. When I pulled it off, the teeth were all bent about three fourths of the way across the tooth, and that is what gave it the "proper" feeling mesh. I had a 17t in my box, so I put it on, but regardless of which holes I used on the motor mount, it REFUSED to line up. I messed with it for over an our trying to get it to line up to no avail. I finally wallowed out the middle two holes on the outside of the mounting plate into a slot, and was able to manually set the pinion to proper lash/mesh. I got it back together, and wow! What a difference! it actually sounds healthy, not like it's screaming in pain as I run it. I am glad I figured it out, but I still have no idea why it wouldn't line up with the Arrma 17t pinion that came with the truck. The only thing I could figure is that maybe it was a bigger spur than normal? Anyone ever seen such an issue?