Working on a cat d3b right now that will randomly stop moving when warm and the pick back up about 6 seconds later. Pump pressure is very erratic between 300 and 100psi. Im am not using a liquid filled gauge and the pressure fluctuates so fast it seems like the needle should break. When the machine quits moving, the pressure will fall to around to a steady (no extreme fluctuations) 60 psi for a couple seconds and quit moving. When is starts to pick back up, it begins jerking and then takes off fine again. The guy just put in a new pump, converter, and pickup tube to try to solve the problem with no such luck. I made a plexiglass cover to use as a top cover so that i could see better. The spring between the relief valve and the load valve is shuddering back and for very quickly just like the pressure gauge. I am under the impression of a aeration problem or even a starvation problem. What sort of sump/pickup assembly does this thing have and what could i look for? I had another used valve body assembly in which the housing bores looked in better shape than the one that was on there so i switch all spools and internals out of one and put it in the other with no change in the issue. Running out of things to check. Lance
Here are the details of the suction strainer. Also check "O" ring seals on the connecting tube.
I have had a problem with the pick up tube inside the case. You can't see it until the trans is out and the cover is pulled from the planetary assembly. I confirmed this by over filling the trans and running it for a short time to check for aeration. I properly cleaned and applied J B Weld to the tube where it goes into housing and haven't had a problem since. Its that #3 in the drawing. It presses into housing...no seal or o-ring. Couldn't see any cracks in pipe so i flipped it over, cleaned all oil off it and sealed it up. It is not a small job.