Cat D4H Torque converter overheating

Thought I'd give you all an update on the machine. Here's some of the additional test and repairs I've tried. Removed trans control valve and installed the updated converter ratio valve, slug, & spring and still low to no converter outlet pressure. Tried adding shims to the converter pressure relief, no change, almost seemed worse. Removed shims that I added and actually removed 2 of the .036" shims to see if anything changed, now seems very lethargic when cold. Run machine until hot, stalled out the converter and immediately drained oil from housing, only drained out about 2 1/2 to 3 qts. so I don't think the converter is leaking. I bought a good quality digital pressure gauge and retested all pressures rather than relying 4 different gauges. Priority valve pressure (tested at steer/brake control valve) - 460 psi low rpm & 532 psi high rpm. Speed clutch 335 psi low rpm & 360 high rpm with LP plug installed. Direction clutch 286 psi low rpm & 307 psi high rpm. lube pump 10 psi low rpm & 33 psi high rpm. Converter inlet (cold oil) only 22 psi high rpm, shouldn't this pressure be around 140 psi ????. Converter outlet 5 psi high rpm in 3rd gear then drops to near zero. Looking at the hydraulic schematic that Mark posted I see the priority valve supplies the trans control valve with high pressure oil. Why would I get correct pressure for my clutches but not converter inlet? The specs for inlet pressure just says it can be up to a maximum 145 psi with cold oil but gives no minimum. I also see a resonator valve inline on the converter inlet circuit, where is this valve located and could it possibly cause a low inlet pressure situation ? I did notice that my high rpm lube pressure is below the minimum of 40 psi. I believe I tested the pump pressure when hot. Either that I need to use a lower scale gauge and retest. Nige, you asked for the serial number - 1986 Cat D4H series II S/N 8PB01285. At this point I'm totally lost as to what it could be, even Cat tech support is scratching there heads. Maybe with the additional info might give one of you the smoking gun I'm looking for. I have to thank all you guys for the input and ideas, this is really a frustrating problem.

What is your converter outlet pressure now. Your inlet pressure is low but 140 is just a max number.
If you have fairly good lube pressure at least we know the oil is getting through the converter without being lost to scavenge pump. Is your torque outlet valve assembled properly.

The outlet pressure is 5 psi then falls to about zero. I've had the pressure relief off and apart, cleaned and reinstalled with new O-rings. It was a little dirty, but other than that, it looked good, there's not much to it. The first time I tested the inlet pressure, I was getting 40 psi, now it's 22. I'm not sure if that's due to inaccurate gauges or from removing the 2 shims in the relief valve. I may reinstall the shims and retest. Just a side note that Cat tech support is saying the the inlet pressure should be 145 psi ? I think they read the spec chart wrong, that is the max pressure cold. I do think that 22 psi seems very low.

The maximum converter inlet pressure as per the spec chart is designed for protection purposes. On a brand-new machine cold typically it might get above 120psi, maybe even 130 but that would be about your lot. I would expect a used machine to register significantly less than that but still above 100psi.

You'll note that every other pressure on the chart is taken with the machine at normal operating temperature, the TC inlet pressure is the only one that's measured cold.

So if my inlet pressure is too low, wouldn't that effect my outlet pressure as well? Does the inlet pressure get it's oil from the priority valve through the trans control valve? What do I need to be looking at to get my inlet pressure up. I know the ratio valve controls both inlet and outlet pressures, that has been updated to the new valve with the spring. What about this resonator valve that's inline. I know it controls hydraulic pulsation, but could it cause a leak or low pressure situation? Where is this resonator valve located anyway.

No exact location specified but it is listed Ref. #21 as part of the transmission control valve.
According to the SysOp it is in the line between the Ctrl Vlv and the converter, so I'd start looking somewhere around Port "A".
There is a Service Magazine for it that is interesting - "A new connector (#20) is used in the end of the resonator assembly in the transmission hydraulic control group on the D4H (8PB, 9DB) Tractors. See the illustration. The new connector is hardened and will better withstand the impacts from the resonator piston than the former nonhardened connector."

start the machine in gear and check pressures. that will bypass clutch #3 in neutral and third speed which is the testing position
but it gets back to low flow either pump performance or internal leak. As I said earlier I would completely bypass the brake /steer valve if just to eliminate completely from the test result

With the way the priority valve setup works it's not beyond the bounds of possibility that a leak in the steering/brake side could affect the powertrain, but it seems weird that transmission pressures are pretty well on the button but converter pressures aren't.
I agree with Mark, bypass the priority valve for the steering/brake system just for a test, send all the oil to the powertrain and see what happens.

Hi guys, I finally have time to do more testing on this. Mark, is their a possibility you could send me some specs for this block off plate that you use so I can make one and also how it's used? It sounds pretty straight forward, just unbolt the filter assy and slip the plate between filter and case? Or just a thought, what about pulling the filter assy back far enough and slip a cut bolt or something in the steer clutch/brake passage to block it off? I'm not sure if there's enough room to pull the filter housing back with all the hoses attached and I believe there is a hard line involved.

this is how I made my block off plate
remove the mounting bolts between filter and case
slide a piece of gasket paper between the filter and case
slide bolts into housing and lightly tap bolts to mark gasket paper
remove gasket paper and punch out bolt holes
reinstall gasket paper and tighten bolts firmly this will transfer the oil hole outline to the gasket paper
remove gasket paper and cut out all holes apart from the oil feed to the brake /steering valve
transfer hole pattern to 1/16 metal plate and cut
leave some metal on top of plate to use as a handle
install plate with gasket to the non seal side of housing

it sounds like a long process but it doesn't take long and will help you eliminate one variable in this problem

So after I make the outline of the oil passages and looking at the parts listing, there is 7 O-rings that seal the filter housing to the case. Which one or ones do I leave blocked off?

Hi,The upper pipe circled is brake steer supply
The lower pipe circled is return
you can block off both both pipes or just supply

As i plated the filter/priority valve for a different problem.
it would be easier and quicker to put a blanking plate under the brake steer valve with no oil passages open at all to isolate the brakes and steering from a leak path.
the only difference would be that the internal oil pipe is still in the equation

After installing plate and my pressures to the converter come back, then the leak is in the steer/brake area and if no pressure change I would assume the leak is in the trans area.

Hi Mark, I Installed the plate and now I have no pressure to all systems. This is what I found when I removed the block off plate, the two pipes that were blocked actually appear to be under pressure as it dimpled my metal of the blocked ports. You say the upper pipe is steer/brake supply and lower is return, should I open up the lower hole assuming that it's actually power train supply? Attached is a pic of my plate.

I am not sure what is going on there. Maybe we used the wrong ports. I checked my plate and it looks about the same but it has been altered for other jobs.
the only thing I can suggest is that you block off the ports at the brake/steer valve, as no oil holes are used at all.
Other wise I am out of ideas at this time

i am having about same problem on d5h , i went thought steering valve and steering clutch and brakes just because of hours,almost 13000, the only thing in steering and brakes that was wore was plates between brake disk. replaced them and seals,then replaced trans pump, no help,i have owned this machine sence 3000 hrs so know what has been done,had same problem around 4000 to 4500, was clutch packs in trans, done it again around 8000 to 9000 hrs and now at almost 13000 hrs same problem, i just new i had never been in steering and brakes or tort convertor, but the presser is now telling me it is speed pack in transmission again, looks like about every 4000 to 5000 hrs does it in. well looks like more fun with wrenches. good luck, and thank yall for help,and keep safe.

Well guys, I'm sure I found the problem. I was about to start removing the trans and tear it down. I drained the trans oil and removed the trans control valve cover to disconnect the shift rods and thought I wanted to find this resonator valve before I went any further just to make sure that wasn't the problem. I removed the control valve and was looking everywhere inside the case and originally found nothing, then I looked down at the control valve cover and there it was staring me right in the face, the damn thing is attached to the backside of the cover. I wasn't looking for such a large valve, it's about 8" long and probably 1 1/8" in diameter. The plug fell out of the end along with the spool and spring. I fished around the bottom of the case with my magnet and found all 3 pieces. I need to order a few pieces and parts from Cat and I'm sure some will take a few days to get. I will post after I get it back together with hopefully good news.

Well done. Never seen one come apart before

Go any photos..?