I have a Bobcat 753C that has a similar problem with the drive motors. I am still trying to resolve the problem myself. The main issue is that the left drive is very weak in the forward direction, and normal in the reverse. Forward torque will suddenly emerge when the right stick is shoved way forward. It seems clear to me that the drive motor is able to function in both directions, but there is some misdirection of fluid pressure that is occurring. My best guess at this time is that the Shuttle Valve (in the motor housing) is causing this problem, and I am presently and slowly working on that to try to find out. It is also interesting to me that the right drive motor seems to exhibit the behavior, except that the reduced drive torque is not as extreme. But, the interesting thing about the right drive problem is that it is exactly opposite the left, such that it is the reverse drive that is weaker. I note that the exact same drive motor is employed on both sides of the 753 (i.e., they are not symmetrical mirror images of each other. This would be consistent with a failure mechanism that tends to inherently favor one rotation direction over the other; and thus, it is the same thing going on for both sides, but in opposit drive direction. I have now heard of a few other cases of this same problem in which similar behavior is reported. I have not yet seen a clear resolution described.