4840 charge pump?

[Craig C]

Still working on 4840. Remain rear pack. System pressure is
shimmed to run 180psi. Tractor shift fine. Lube pressure
drops with temperature increase. We went through the clutch
pack in the shop. Dad said he had seen worse and it would
pump oil. I didn?t see it myself. I?ve been wanting to think it
needed a new trans pump ever since we got it back together.
Shifts fine from idle, but needs 1500rpm or better for steering
and hydraulic functions. It acted up when I tried to fold
bushhog. So I stopped and checked the oil. The oil was hot,
but the transmission cooler lines were cool enough that I
suspect no oil is flowing. Is this pointing towards a bad
charge pump or a valve not operating correctly? Is it possible
that the charge pump is satisfying the transmission, barely the
hydraulics and nothing goes to the cooler ever?

 

[buickanddeere]

you have it figured out .

 

[dwag]

IIRC,on a 4650 few years back, there is a cold oil relief in circuit by oil cooler that can came apart and pieces traveled to another check valve in small aluminum canister on upper LH side above clutch valve. May not be your prob but thought I throw that out there along w/possibly major leak in hyd unit like SCV or hitch valve etc.