Need help! bobcat 963 leaking hyd. in chain case

[BC963]

I recently purchased a 963 bobcat, knowing it had hydraulic leaking in the chain case. The guy I bought it from said he replaced both drive motor shaft seals and it didn't fix the problem, the motors are strong and pull straight. It leaks about 1gph when at idle, not working and 2gph when working it doesn't seem to leak when the machine is off after it has lost pressure. He believes it to be an internal drive motor seal and the motors need to be rebuilt, it seems to me there would be a loss of power or something wrong with their operation - am I correct here? Is there somewhere else hyd. oil can get into the chain case?

I've checked one case drain filter by the hydrostatic controller - it was clean. Is there more than one on this machine?

Thanks for any help.