I have an AGS ser# CAT 345 that will not walk. When you push the pedals the tracks tension up but it doesn't move, if you keep the pedals pressed the motor lugs down and tries to stall. There is also a significant time lag when operating the two joysticks before the machine will operate and when it does there is no fine control. Has had MCV, swivel and pump pilot pump rebuilt in the last twelve months. Any idea's.