Long time listener, first time caller. Appreciate any pointers D6H s/n 9KJ01130 , 9189 hours This has been an on and off project for the last 6 months , now busy season is over we will be able to dedicate a some uninterrupted time to this machine. Original issue- 200 hours ago, machine would not move. Found the two pump couplings to scavenge pump had failed (3E-4880 ) pulled the shaft and found the pump had locked up. Oil level okay, no operator complaints previously. Drained fluid, flushed system, new screens and filters installed, new pump and couplings. Machine ran another 6 months. (did not test any pressures at this point of installing new pump) Second issue- machine stopped moving, found failed couplers again. Pump did not "feel " correct spinning over by hand. Pulled axles, dead loaded machine back to the shop. Pulled pump, opened it up, scaring internally, looked like pump was run dry. Fluid level adequate both by dipstick and seemed the correct volume came out while draining the machine. At this point, opened up the transmission back cover and looked around, physically saw clutch plate and friction disc failure. Pulled trans . No obvious rags or foreign items in the oil sump. Installed rebuilt trans, installed new pump, dumped oil in top of pump prior to starting, new filters, screen fluid etc. Started up dozer with gauge attached. 0 psi on port D (trans lube pressure) Machine will start and move but did not move it around it much after saw 0 psi. checked with a 0-10 gauge and needle does not move. unhooking the gauge from the hose, fluid does not come out unless you high idle, at that point only a small amount , which you could hold back the fluid with your finger. I will note, that the pressure test port is slightly different than the service manual photo. - see photos- Opened up and visually inspected the torque converter relief valve and priority valve, no visible damage. Pulled the screen and magnet below the scavange pump and it was still like new. Big picture thought - it seems we are not getting adequate fluid to the transmission pump and that caused the original failure , low lube pressure causing the transmission failure. Appreciate any thoughts on where to look next.
Are you using a gauge of max scale 25psi.? If you aren’t then it’s highly unlikely that the pressure will be enough to register.
Thanks for a quick reply, used a 0-10 PSI. It does not move the needle even at high idle.
I might have missed it but have you checked the suction side of the pump for air leaks? Have you checked any other pressures like the torque converter in and out ect? Nige will help you get to the bottom of it I’m sure and be far more help than me.
New o - rings on the "L" shaped tube that holds the screen and magnet, no external leaks or cracks. Put a transducer and air bladder at the top of the tube and it did pull fluid up the L shaped tube. Yes checked all the other pressures, and I cannot find that page were everything was written down. Will retest when tomorrow when the temps come back up a little. I don't recall anything being way out of spec.
Did you check the steel tubes inside main case I have seen them break always made a habit of pulling on them to see when I had transmission out
Couple of thoughts. Is the 0-10 gauge "known good".? Have you tried removing the quick coupler from the trans lube pressure test point and (carefully) crank 'er over to see if oil comes out of it.?
I would have to check but I don't recall ever testing anything at the plug in the picture, the best thing to do is remove the back plate off the transmission then start the engine, now look in at the transmission and you should see oil flying about to your left and right.
Did not, had thoughts to pull the trans back out and re-inspect.
Tried multiple gauges. Yes took the hose off, get the slightest amount of oil at high idle, but you can hold it back with your finger.
If you start it with cover off transmission you might be able to see leaks
I must apologize. While trying to get info & supply answers earlier I was in the middle of helping #2 son paint his lounge and as a result I wasn't as on the ball as I would normally expect to be. Confirming what @tctractors mentioned above about pressure tap locations. On Page 15 of the attachment you will find the illustration below. Ref "C" is the transmission lubrication pressure tap. SENR3240 is listed as the correct Test&Adjust document for a 9KJ-prefix D6H tractor. Apologies for the fuzzy photo but it's the best there is. The photo from the manual posted in the OP appears to be from Cat Publication reference SENR3534 which I don't think is the correct document for this Serial Number of tractor.
Nige, Thank you for the literature. It appears the literature references a different style transmission than our dozer has. Here is a photo of the back of the trans. Our unit is a "diff-steer" tractor.
I hope this may help. From this parts print it appears as though the transmission lubrication pressure test point "D" is on the side of the rear case. However there does not seem to be a plug in that location despite what the Parts Manual says - see below. As you can see from the attachment it (allegedly) would have had a quick coupler attachment (Ref # 5 thru 7) on it. Where exactly are you connecting to.? Do you have a photo of the back side of the transmission case taken from the right side of the machine.?
I may be wrong but I seem to remember them discontinuing that tap on the side
That wouldn't surprise me. The Part Number has changed 3 times (7T-9133 -> 144-7876 -> 190-2278) but I see no documentation explaining what the changes were.
look at post 1 pictures
Are you thinking this one.?
no the one on the right side of case is absent
I saw that. I just wondered if the one I circled on the back had replaced it.
I seem to remember top but i can't remember many times checking lube pressure seems like I remember the spec to be like .5 to 12 psi I would think you could hold that with your finger if you were brave enough
All, A couple updates. 1) as you mentioned , there is no port d on the side. the plug on the top and on the back are both connected to each other 2) see photos of plug removed from port d top and back, no fluid comes out, both photos taken at high idle. 3) re ran all of the pressures, and you can see many of them are deficient
Also a note, we do not have a test location at "F" What was strange, in SIS, I found similar literature to what nige posted the other day. But the ports did not match at all. With this "D6H series II" paper service manual the ports seem to match up more closely to our machine.
Those pressures sure look like primary pressures,you said transmission was rebuilt was the valve gone thru There is a screened orfice in the control valve it is plastic they have a tendency to break and plug the flow to load piston pressures at p1 and p2 will be similar to test with load piston plug removed
I don’t see that you have tested torque converter outlet pressure. This is important because torque outlet goes through the trans cooler and becomes lube oil pressure. Is it possible the torque is fubared and dumping all that oil through the scavenge pump?
Based on those numbers you have far bigger problems than simply low transmission lubrication pressure. Seconded. On a transmission valve strip/inspect we used to replace all the screened orifices in the valve with new as a matter of policy, whatever the ones that were in there looked like. There are also a couple of orificed plugs in the control valve, one of which has a screen in it. Was the transmission cooler removed and cleaned (at the very least) or preferably replaced while the transmission was out for rebuilding.? Have you cut a transmission filter for inspection recently.?
The trans cooler at time of change was pulled, blew out with trans flush and air. I dont recall much debris. next plan of attack will be to pull the trans filter , cut open, re pull the trans cooler , pull the valve body change the orifice plugs. I will report back Thank you for the help so far
I have 2 strips of 1" x 1" angle that I bolt the round pressure cap to that you can see held in place on the back cover plate, with the cover plate removed and the pressure cap supported it allows a good look inside to see what is happening, I have just one customer that runs a Dash 11 and I gave him my Service Manual, I still have a parts book some place but there is a modulation control valve if I recall bolted under the floor plate below your left foot that might be worth checking out, the pressure reference looks odd as' what was the main pressure that lifts the brakes, this pressure has to be reached before the transmission gets any oil pressure that is set lower than the brake control pressure.
Before pulling the oil cooler and filter I figured to try this while it was together. See attached photos, there is a "geyser" of oil coming up from the valve. Having never ran one without a cover, wasn't sure if that is what is supposed to happen or not. thanks
They dump a lot of oil in neutral I want to see if a lot of oil coming from steel lines I think I would pull the valve take it a part flip the section with the spools in it you will see a plastic piece in a hole pull it out check inside the screen for a loose piece of the top they used to be about a dollar fat chance of them being that cheap now
The valve with the spring visible and the oil tubes going into it needs to be removed and stripped and checked, it's the pressure control, you might want to think about pulling the valve chest out and checking also, it is heavy I would use a fork truck tine to lift it out, if you have a clutch piston seal blown it is easy to spot as the oil gushes out of the gear case.
All, Just an update. Pulled the trans, and tore it down to see what we did or didn't have going on. 8D9739 and 8P2023 both missing. The guy that "rebuilt it" didn't have much to say. We ran through all clutch material looked new and all other seals were there. Tested all the pressures and they are now within spec. Will get the floor boards and drawbar back on and let it push some dirt later this week. I am not 100% on what the initial cause was that we lost the pumps and then the trans but we will see how it performs. Thank you to everyone that replied.
I have my fingers well & truly crossed for you.