Hello, I have a cat D4H dozer serial number 8PB02082. Last fall the transmission started to overheat and when you try to push dirt it would lose all transmission power. I changed the Transmission fluid with cat TO-4 30w along with the transmission filter and cleaned the suction screen. It still was still overheating so I parked for winter and now the snow is going away I need to work with it. I found to testing and adjusting operation for the transmission and went through the the pressure test on the transmission and got the following readings: Converter inlet pressure (p3) 0 psi, Speed Clutch (P1) low @ 330 psi / high @ 360 psi, Direction Clutch (P2) low @ 290 psi / high @ 290 psi, Transmission Lube low @ 0psi / high @ 17 psi, Converter outlet pressure 0 psi, Priority valve 525 psi. I have taken a part the torque converter outlet relief valve and cleaned it and checked for anything out of the ordinary and everything in there seemed to be fine. Following the power train hydraulic system schematic I'm thinking the issue for the low to no pressures is something in the transmission control valve is not letting the fluid through or a major leak in the valve. I'm planning on taking the transmission apart later this week to I can get to the control valve. If anyone thinks that it might be something else like the the torque converter please let me know. Just wanting to see if anyone has a different idea of what it might be before pulling the transmission out
Here's the SysOp so you can understand better how the powertrain hydraulic system works.
When our D4H acted like that, it was a pedal or two sticking. They pivot on needle bearings, that were seized up.