I have a 1979 Cat D7G serial number 92V8438 dozer and I am experiencing a drop in power when pushing half to full blade of dirt up an incline. I have checked the transmission pump pressure and it is 375 at minimum throttle and 460 to 475 at high idle. Engine at operating temperature. Need help diagnosing the problem. Trying to determine if it is a torque converter issue. Transmission temperature does not get anywhere close to overheating. Replaced transmission oil filter, cleaned transmission magnetic strainer,--small amount of debris on the magnets. Removed scavenge pump strainer from torque converter housing, did find orange blobs of silicon on strainer screen. It appears that the previous owner had been into the bevel gear housing and shows signs of orange silicon on steering clutch cover housing. Any help in determining where loss of power is would be appreciated.
I would be checking fuel pressure and turbo boost pressure first. Without looking it up, chances are there is also a diaphragm somewhere in the vicinity of the injector pump that will have something to do with the boost pressure.
You need to be more specific in your description. Loss of power, pretty vague. Are you losing engine RPMs, or just ground speed??
It seems to be losing ground speed, rpms change very little, but when I get into the load I can give it more throttle, speed may slightly increase, also when I change direction throttle up I will get a puff of black smoke from exhaust,
Try lifting the floor plate in the cab and observe the drive shaft between the converter and the transmission input. Engine idling, transmission in neutral, service brake applied, shaft should be spinning. Engage any gear FWD or REV and the shaft should stop turning like someone stuck a bar through the universal joint. Report your findings.
Removed floor plate from dozer and with engine at idle speed I engaged transmission in forward and reverse multiple times and the drive shaft stops immediately, but spins in neutral position. Is next step converter inlet and outlet pressure tests?
You need to do those tests at some point so maybe an idea to do them now. I’m guessing your tractor does not have a tachometer. So you need to get hold of a phototach and take the RPM numbers for high idle no load and also with the machine stalled against the brakes in 3rd speed forward.
^What Nige said
Took some readings. RPM reading at full throttle was 2100 RPMs. Converter outlet pressure was 90 psi--manual said it should be 42 +/- 5 psi. Converter inlet pressure was 150 psi--manual said 135 +/- 5 psi at max throttle with cold oil. Transmission speed clutch pressure at low idle was 330 psi and at high idle 425 psi. Directional clutch was 270 at both minimum and maximum idle.
What was RPM with brakes on, full throttle in 3rd gear?
And with everything warmed up to normal operating temperature.