I agree with Tx Jim that it is more than likely the hydraulic pump drive coupler. If you have caught it in time all you will need is the new isolator bushings.
Just reach in and see if you can rock the pump coupler back and forth. If you can move it at all it is bad. Just remove the clamp bolts and nusts. The two halves will come right off. I just take a sharp chisel and cut the bushing paralell to the shaft. They are just a type of plastic. If the pins have not worn the coupler halves than just install the new bushing. Then clamp the two halves of the coulper dive back together and you done.