I just bought a D6C, 76A5577. I tuned it up, changed the fluids and fixed minor repairs. There was water in the transmission fluid. I changed it out a second time after warming it up slightly. Looks good now. I went to work with it today. Once the transmission warmed up, after about 30 to 40 minutes, the power faded and then the power shifter wouldn't engage in forward or reverse. It works fine after I let it cool down a bit, but then eventually will fade and do the same thing. The temp gauge for the converter reads between 1/3 and 1/2 of the way through the green when it begins to fade. The first time the power faded, there was steam coming out of the transmission vent and dip stick. It was probably left over moisture. It didn't do that the second time I worked it. How hot does the oil get in the converter? I didn't think it would get hot enough to make steam. When I cleaned the strainer and magnets, I didn't find any large pieces. See photos. It all seemed uniform and small pieces mixed as a black sludge. Same with the drain plugs. I haven't tested the pressure yet. If the gauge works, then it shouldn't be too hot. The outside temps are in the 20's. It takes several minutes to warm up enough to move from a cold start. Could the pump be worn out? Looking for some feed back. Thanks Keith
Filters and magnets look quite dirty to me. Have seen worse , but generally it was in a machine that was grenading. Might be a good idea to do all the filters again as maybe something is getting plugged. A set of tests on pump pressure would be good idea. Maybe someone will post a picture and minimum pressures. And yes water in system will steam when the oil gets around 200 F. Transmission oil can run a fair amount more in tempeerature. Is the transmission oil at correct level, as low oil will cause lots of problems. By the way, what kind of oil are you using in it. Simon C
Well over 200 DegF when the tractor is pushing, probably up to 230. Plenty to make steam. First question would be what oil are you using in it.? When talking about water in transmission circuit a thought comes to mind while looking at the photo of the transmission suction screen. I can't remember if this is the case with your tractor but if the clutch friction discs in one or more transmission clutches have the paper-based friction material then what's in that screen looks just like it.
I beleve red line on gauge is 230 Pretty sure tran disc are splintered bronze steering clutchs on the other hand could be
I'm using TO-4 30w. It didn't produce any steam after I let it cool down and then run again. Probably just remnant moisture. I need to pick up an infrared thermometer to confirm that the gauge is correct. It's hard to imagine it over heating in 30 to 40 minutes. I was removing trees, so it was only intermittent pushing. Water would probably be a problem for cellulose based friction plates. Hope that's not the case. The screen was full of that golden yellow stuff.
The fluid level was adequate. I replaced the filter element a second time with the second oil change. I didn't check the strainer again. I'll do that just to see what's there.
You need to get the floor plate loose, and after running it until it stops moving, see if the driveshaft between the torque converter is spinning or stopped. If it stops when you put it in gear and increase engine RPM, your torque converter is probably worn out.
You said it would not engage forward or reverse do you mean the shifter is spring loaded to nuetral ?
I know this probably won't help you much but.....Too bad the transmission/torque converter screen is in such a difficult location on these old D6C's A trap door in the floor over the filter would have solved that problem. I think that filter/screen doesn't get serviced very often, in many cases if ever. My D6C 76A5579 looked exactly like yours when I got it a year ago, My situation was similar to yours, machine had water in the transmission, screen was full of fuzz. I did a complete fluid filter change and cleaned the screen, put T-04 30W in the trans. and new oil and filters in the engine, before I started working it. the machine worked well. After that one time when pushing a long distance carrying trees, stumps and some dirt it stop moving. I was in 2nd gear and it stopped and did nothing. I let it sit for maybe a minute or two, and it started working as it should. I never tried pushing much in any other gear but 1st after that and everything worked as it should. I've since sold the machine and the man that bought it said he worked it pretty steady last summer and it worked great. Why it did what it did to me is still a mystery. I hope you get yours sorted out, good luck.
Yes, as the symptoms progressed, it would feel different, a little harder to put into position, and then as the power would fade to the point that the machine wouldn't turn, the shifter would not move into the forward or reverse positions. Spring loaded to neutral is a good description.
So as the oil gets thinner due to heat, you lose pressure. So either worn pump or it is sucking air in somewhere as the oil heats up softening o rings or flexible joiners. Water could be getting either from poor sealing of gaskets around the clutches area, or through the trans oil cooler.
I'm not at all familiar with how the control valve works, would low pressure not allow the shift mechanism to operate properly? The old 7H I worked on had a cable that operated a spool for direction.
On the older ones the safety valve will kick the lever back to neutral at low/no pressure.
Hopefully a new charge pump will get things sorted out.
Your oil pressure is very low The safety works with a spool and a sleeve that conpresses a spring to allows shifter to travel into gears. It was basicaly to put transmission into nuetral if tractor was shut down in gear. I would also check the suction lines Like my old buddy used to say just because its not leaking oil doesn't mean it's not sucking air
With My D6C the shifter would move as it always did, just not respond so that was different from yours.
Later or updated version had the spring setup removed if you shut it down in gear you have to physically put it in neutral to reset pressure control valve
If you haven't got a Parts Manual yet I suggest that you get hold of one ASAP. The online system has very little information on the 76A machine, and even less on the equivalent powershift transmission D6C models built in the UK, Japan, and Australia in the same era. The manual you require is either of Cat Publications reference UE035000 or 0350000. you may find a used paper copy in an internet marketplace somewhere.
Hy Shimmy1, Sad to hear those problems, as usually that kind of situation with TXM´s not engaging or not pulling eventually require some heavy fixing, That does not mean u´rent a lucky one and only a ring leaking... Nevertheless its important to narrow the problem to one of 3 components in the system, Oil Pump , Torque Converter, Main Transmission. If ther´s a oil pressure problem, that comes with heating the fluid to normal temps, probably the pump is not puting out enough flow either due to leaks or pump degradation, engagement might not be happening TXM clutches may be slipping, TQ convertor may not build turbine traction pressure.... in the end all that will show in the pressure ports. Basically u´ll need a TXM repair/test manual, where u can check correct pressures, once u find out they´re low, one can check for air leaks or collapsed hoses in the suction, ultimatly inspecting the charge pump will definetly tell where the problem lie. Charge Pump and oil is the heart of the system, without it the TXM clutches do not engage and the TC will have traction problems, and brake problems may also be present. Good luck with it
Pump pressure ? cold and hot?
I replaced all of the components on the suction side of the pump that could cause a problem: seals, hoses and clamps. I worked it hard today for a few hours, brought it up to running temp and didn't experience loss of power or other symptoms from pressure loss. I must have been sucking air on the suction side of the pump.
Sucking air on a transmission suction side of a pump will cause all kinds of problems. Thanks for replying back. Old hoses or o-rings can do lots of things. Simon C