Ok so I am not new to RC but new to the Cup Racer. I am having an issue and have read through this entire thread and have not seen a solution to my issue that I believe.
I assembled my car and installed a Sidewinder 5700. As for battery I am running a Orion Lipo 3200 20C with Deans connections. When you first apply throttle the car seems to stutter it also is extremely loud.
After the first time the noise scared me so I completely disassembled the drivetrain and double checked assembly. I noticed the rear yoke on the pinion was hitting the three screws that hold the spur gear so I filed them down for clearance and re-assembled everything. The noise is definitely quieter but the stutter issue is still there. I have double checked everything from pinion/spur mesh to the diff's front and rear. The only thing I can think of is the gear ratio is too high at 5.28. Anybody else care to point me in another direction before I go out and spend money on multiple pinion gears?