from what I have read and by looking at the tractor the sump is separate to the gearbox and the hydraulic pump which is situated on the left hand side of the motor near the injection pump has 2 lines running to it the larger of which goes to the bottom of the gearbox housing and I assume to be the hydraulic pump intake line and the smaller would be the outlet/ pressure line. also the owners handbook which I downloaded from this site says 30 weight for engine and 80 weight for trans and hydraulics so this also makes me think that the engine and trans/hydraulics are linked to each other but the sump/engine are separate.