Hi! Working on a deere 540b skidder, no hydraulics working, testing at the pump finds 0 charge pressure until about 3/4 throttle, then the gauge will come up to around 150 psi but drops to zero again at idle, I've tested the transmission pump pressure at 175 psi, according to the book the transmission pump charges the main hydraulic pump, either my oil is bypassing somewhere or tranny pump is weak and can't flow enough. Any ideas? Please.
oops!
So the transmission works fine? I don't know that setup, but guessing based on other Deeres, I'd look at the pressure control valves on the transmission. It looks like that has four spools. Other transmissions feeding hydraulic pumps have three spools that control the trans, hyd and lube pressures. If the transmission has plenty of pressure then look at the next valves down in the priority/pressure order.
Thanks for the reply, yes the transmission is working fine, after studying the book a lot I agree with you, the filter relief and the oil cooler relief can both dump the charge oil back to sump, that valve is a real sweetheart to get to but that's where I'm looking next.
Having the same problem with my 540B. What did you find the problem to be?