I've got an old D5 (96J) that runs fine for 2-3 hours and then the torque convertor temperature starts climbing eventually pulling up the engine temperature. Been through the torque replacing seals and bearings. All looked good. Found that the pressure was a little low on the torque input side and shimmed it up to increase the pressure to specs. Screen is clean and just put in a new filter, but still runs hot. I've ran standard hydraulic fluid in it for around 5 years and never had any problems before. Does anyone know how tractor hydraulic fluid compares to true Cat fluid? From what I understand, it sounds that the TC is flooding. My manual says the output from the TC is controlled by the orifice and it's not adjustable. Is the orifice in the TC housing? Any other ideas on things to check? I'm not sure where to go next.
Overheating can be caused by torque converter leakage, a scavenge pump that isn't keeping up, a clogged oil cooler or a lack of transmission pump flow. Check the transmission lube oil pressure. It is the last to receive oil in the circuit and should read 5-9psi with engine speed at high idle and selector level in neutral.
Oooops. Double post.
The orifice that controls the TC out pressure (well the flow at least) is built into the TC housing at the oil outlet port. As you rightly suspect it's non-adjustable. To a large extent TC out pressure is a direct function of TC in pressure. OM's suggestion of the trans lube pressure is the way to go because it's the last thing in line to be fed with oil. If you have internal converter leakage you would expect it to be low to the point of being almost non-existent. Standard hydraulic oil does not really have the necessary additive package for a powershift transmission. I would try it with an SAE 30 TO-4 specification oil.
on my 96J D5 i run straight 30 wt engine oil in the summer, and 10 wt engine oil in the winter in the transmission,torque convertor, thats what cat recommends,same in the older cat 518 skidders. I'm pretty sure the hydraulic oil is way to thin. Don