Caterpillar D7G Bulldozer, Powershift Transmission. S/N 92V6463. Transmission slips on occasion, seems worse on hot days. Normally, clunks into first or reverse fine, good solid clunk, and doesn't slip. When it doesn't slip, delivers plenty of power to finals fine. Machine has 9200 hours on it. Nothing been done to tranny that I know of. I have changed the oil I think three times. Always looks good, replaced with 50 weight gear oil as specified. I have the Cat manuals. Here's my thought: The tranny itself is good (gearing, bearings, clutches) I think. The gear and mode clutches (fwd and rev) are selected by the lever and actuated by servos (pistons with O rings in a hydraulic bank I think). When the machine is cold on startup, etc, seems to clunk in with a vengence, runs good. When hot, just doesn't clunk reliably. Usually, a second try works, but I hate that slipping, that is hard on the clutches. Yesterday I noticed it not only slipped in first which is the only gear I use, but also fwd second and third. And it slipped in reverse also, which I really haven't noticed in past. My thought is the servos are not getting full pressure and flow when hot, and / or O rings are getting tired. Oil level is right on, tranny doesn't leak. I don't think I have changed the trans oil filter in the 700 hours I have put on it. Dealer claims he did when I bought it. Seems elementary, but I haven't. Dirty filter will restrict flow and pressure. I will of course. But that would be too simple and too good to be true. Need your help. Thanks.
As you will note from my previous questions, I give a tip. I really need the answer soon and I need a high level of detail, but I only have $19 in PayPal right now, but I want to get started. If you help me with this, you can imagine how tranny problems can be stressful, I will be more generous. Thanks. Dirck