Transmission on 1987 cat dozer D6H 4RC00581 has zero lub pressure. Even with gauge removed from test port line zero fluid flow. Other test pressures are about 75% of normal. Just purchased dozer and don't know pass history. Dozer operates normal but after a few hours trans temp rises to a point where the gear selector becomes intermittent in all gears. The transmission was found to be over filled when first bought. I think the previous owner was trying to compensate for no lub pressure. Ideas please.
What trans temperature do you have at the time you start to lose gears.? Is the gauge in the red.? If it is has the cooler been checked.? Are you measuring pressures straight after startup or with all systems at normal operating temperatures.? How about posting the actual pressures you are measuring, at least for pump, P1, P2, converter inlet & outlet, and the Priority valve.
sn is 4RC00581 p1 250 cold p2 210 cold sorry that all I have no fluid coming from the trans lub tp even with adapter removed main filter found clean start losing gears around 200 degrees F
Just FYI but pressures (apart from converter inlet) are supposed to be checked with the machine at normal operating temperature, so I would say your values are even further away from specification than they appear at first glance. It might pay you to run the pressures again after the machine has been warmed up, then you would know how much drop you have from cold to hot. If you do run pressures again try to get all of them as listed above, not just P1 & P2. Have you pulled the screens (see below) on the suction side to look for particles, metallic or otherwise.? It will require the belly guard dropped to gain access. If the screens don't produce anything of note (take photos an post them here) then I would suggest the next step would be to pull the pump and have a look inside. EDIT: That may be the wrong illustration (for a direct drive machine instead of a powershift) It may take me a while to find the right one.
Here you go. Directly under the transmission pump suction.
Thank you Nige for your input. Here are the pictures of the input filter to the pump. Did not find a screen in the line coming from the torque converter. The listed pressures below are with the dozer cold but pressures did not change with a transmission oil temp of 80 degrees C. With the belly pan removed I had an accident were a branch came up and broke the oil line from the oil cooler to the transmission. This is the line I'm measuring zero pressure but when the line broke it did have fluid flow like a garden hose. For trouble shooting purposes I removed the shims in the priorty valve to give more fluid to the torque converter. Thanks again, William L-pump pressure 400 F-priority valve 350 A-converter input 85 E-converter output 43 D-transmission lub 0 Shims removed from the priority valve- L-350 F-300 A-100 E-60 D-10
If you want to install one the Part Number is 3T-6471 and it's #23 in the illustration in post #5. Fits right into the end of the hose. The oil coming out of that busted hose is NOT transmission lube pressure, it's the flow of oil back from the cooler to the transmission case (which is open to atmosphere provided the transmission case breather isn't blocked) and not likely to have any measurable pressure in it. Are you measuring trans lube pressure at Tap "D" in the illustration below.? If you are then you are correct in your measurement location but the pressure you are measuring is not what's in that hose.
Yes, I'm measuring trans lube pressure at tap-D. Do you think the pump's input filter is contaminated enough to restrict flow to lower pump pressure?
OK, so you are measuring at the correct point but the pressure you are measuring is not what's in that hose. If you cleaned out the one that you found and the other one isn't even there then the answer is no. However .......... hold the bus. I just looked closely at your photos of the screen in the line from the transmission. My apologies I only glanced at the thumbnails previously. Something's fcuked big-style. The amount of metal on the magents indicates a "hard" (not clutch in other words) failure somehwere in the transmission. Cut your losses in terms of more diagnostic time, it's transmission out time. As well as the transmission rebuild you are also going to be in for a converter strip & clean as a minimum, a new transmission pump, minimum of a cleanout of the cooler but probably a cooler replacement, and a cleanout of every line in the transmission hydraulic system. The debris from that failure will be everywhere.
Thanks, Preparing to pull the transmission. I'm thinking excessive wear in the transmission may be causing some of my low lub pressure. When I was playing with the shims in the priority valve and got the converter output pressure to specs, the lub pressure was still about 70% low. Does this make sense? Pressures with shims removed from the priority valve- L-350 F-300 A-100 E-60 D-10 Thanks again, William
Answer to your question - probably. Be sure to pull the pump (it will most likely be scored inside & therefore toast), converter, and cooler at the same time as per suggestions above. I suspect you will find that fine metal swarf that was on the magnetic screen has got almost everywhere in the system.
Here's a picture inside the rear pto after removing the inter and outer races of the rear bearing, All balls where gone. The gap is between the case-as and carrier-ring. So this at least one place I'm losing pressure.