The motor feels strong. It doesn't cog or anything and the magnets on the rotor feel strong. I don't think it is the connection to the battery that is bad as I changed ESC's and still have the same problem. I can only guess maybe the leads from the motor causing too much resistance? Or perhaps the connections underneath the plastic cover on the motor are bad?
Also, I know the shimming between the pinion and spur is good and not loose. Also, the drivetrain in my car is very smooth especially with my elite RC mount.