Hi anyone ! I have been struggling with this cat d5h transmission. The machine works very well while the temp is still cold. As soon as the transmission temp gets to normal or above, it won't select 1st gear. 2nd and 3rd works fine. It has damaged the 1st gear ring seal 3 times now that have been replaced. I have replaced the transmission pump, overhauled all valves and brakes. What else can i look for? Any help will be very appreciated. Henk
Do you mean that you have removed and disassembled the transmission 3 times..? Did you do any pressure testing of the transmission at any time..? If so what were the results..? To get the correct technical/test & adjust specifications please post your machine Serial Number.
Pressure test is the number one tool to diagnose the situation. Follow what Nige recommends. I just did my D6H this past summer. Once we tested all pressures we knew where to look once the trans came out.
Another question. What type & viscosity grade of oil are you using in the transmission..?
Nige Yes the transmission was removed 3 times. The mechanic did take pressures. All the pressures are normal at 250 bar while the oil is still cold, when it warms up the pressure drops to below 100. I will let you know what the serial no is, I don't have it with me.
We use SAE 30 oil. The mechanic also noted that once he stops the engine, the suction pipe at the transmission pump has no oil in it. Once you start up it fills up again. He thinks there could be a leak in a pipe somewhere.
What sort of SAE30..? There are many different types. 250 bar is about 3600+ psi, do you actually mean 25 bar..? That would make more sense.
Nige The CAT D5H serial no is 8RC01753 . We have measured the pressures of the transmission. P1 and P2 at the back measures 215 PSI. The pressure at the transmission filter housing measures 40 PSI. I am told the pressure at transmission filter housing should be above 200PSI. The machine works perfect and selects all gears for the first 1h30min then it becomes difficult to select first gear. If you the shift quickly between forward & reverse it selects a gear and works fine until you have to move in the opposite direction, then you start battling selecting the gear again. The transmission temp moves to aprox 3/4 of the gauge. We use normal SAE 30 motor oil in the transmission. I have overhauled the brakes, priority valve and the control valve and fitted a new pump but still have the same problem. Any suggestions please!!!!!!
I think you need to do the pressure measurements again. P2 (Direction Clutch) pressure should always measure around 55psi less than P1 (Speed Clutch) pressure. The specification for P1 is 370+/-15psi with the oil at normal operating temperature, the transmission in 3rd speed forward or reverse and the engine at full RPM. Therefore P2 should be somewhere in the region of 315psi. Both those numbers are way higher than what you say you have measured. I'm also doubtful of the location where these pressures were measured because you mentioned "the back" yet the pressure taps for P1 & P2 are on the front side of the transmission under the cab floor. The pressure at the transmission filter housing is really not relevant but in any case it should not be as high as 200psi otherwise it would blow the filter apart. If you want to measure transmission lubrication pressure the tap is on the front of the transmission directly below the taps for P1 & P2. With oil at normal operating temperature and the engine at High Idle the specification is 19+/-4.5psi and at Low Idle it should be a minimum of 1.5psi. If you would like a complete copy of the testing procedure which includes the full range of both transmission and torque converter pressures then drop me a PM with your email address. From your posts it would seem as though what you are being told (by the mechanic?) appears to be completely at odds with the machine test specifications. I think you need to either change your mechanic or get hold of the right information and so be the one telling him what to do rather than the other way around. You operating symptoms give me every indication that you have an internal leak somewhere which will obviously increase as the oil gets hotter and its viscosity falls. The fact you have replaced so many clutch piston seals (and even though you are using the wrong oil) could potentially indicate wear in either the clutch piston housing or maybe even the piston itself, or both. I am assuming that is the seal you refer to when you said in your OP .......... ......... correct..? Lastly you are using an incorrect oil. The SAE30 viscosity is correct but the oil should meet Caterpillar TO-4 specification for use in powershift transmissions which contains additives compatible with the friction materials used in hydraulically-engaged clutches in a transmission. Normal motor oils do not have said additives and therefore do not meet TO-4 specification. This could (and I say that advisedly) be the root of all your problems but it might take something a bit more complex than an oil and filter change to put things right now they are so screwed up.
Nige Thank you very much for your advise. I really appreciate your time and effort. If you could send me the test procedures at you mentioned to [email protected] Kind Regards
P1 and P2 test points circled. trans lube is plug at bottom right of photo Mark
Hi Henk, Have you found the cause of the transmission problems? I have the same problem, and I don't know where to look. Maybe you can help me and share information.
I suggest you try to contact Henk via his email he mentioned above. You probably won't meet him here since he last logged in in 2016.
It is unlikely he will reply, he has not been seen on the forum for over 5 years......... Start with the basics. Machine Serial Number, symptoms, what have you done so far to diagnose the problem, etc, etc.
1DD06056 TRANS 3BX01954 PROBLEM: After heating the oil, the transmission stops driving I measured the pressure P2 after heating up to a maximum of 3 bars. I replaced all the seals on the clutches. the bulldozer drives normally for about an hour, after which it stops driving. Tomorrow I'm going to take the pressure again.
Does the transmission stop driving completely in all gears.? Or does the transmission only stop driving in a certain speed (e.g. 1st speed both forward and reverse), in all forward speeds only, or in all reverse speeds only.? Do the pressure measurements in psi or kPa please. See attached for the pressure testing procedure. Also I suggest checking pump pressure (at the transmission filter housing), P1 (speed clutch), and P2 (direction clutch) pressure with both cold oil and hot oil even though the testing procedure says to do the checks with the oil at normal operating temperature.
Thanks for the help I'll do the tests and let you know.
Please can you answer the question from above regarding which gears the transmission "loses" when it gets hot. Is the transmission oil temperature gauge in the red zone when the transmission stops driving.?
loses gears 1,2 Honestly, I didn't look closely at the indicator.
OK, thank you. After you do all the pressure tests run it until the transmission quits driving in 1st & 2nd speed then note the transmission oil temperature please.
Hi Nige, Update of the situation . I adjusted the forward / reverse levers and gears 1,2,3. The machine was hot above the 178F. I made measurements on ports P1, P2, A, TC. (psi) After observing the machine, it seems to me that the problem is the inability to choose the forward or backward drive. Gears 1,2,3 engage correctly (provided that front or rear driving is selected). I also noticed when I move the steering levers, it reacts faster to choosing the direction.
Pump pressure at 435psi is good, so it appears as though the pump is OK. The pressures for P1 & P2 are somewhat low. With the oil at normal operating temperature P1 should be around 370psi and P2 around 315psi. Also the values that you measured do not make nmuch sense. For example, if there was a problem in the 1st speed clutch the P1/P2 pressures would be low in 1st speed in BOTH forward and reverse directions. Similarly if there was a problem with the reverse direction clutch P1/P2 pressure would be low in ALL reverse gears, not just 1st speed. You mention that if you move the steering levers the transmission directional control operation improves. I suspect that you may have a problem in the steering/brake system. I attach the Sysem Operation where you will see (highlighted on Page 6) that the steering/brake is given priority before the oil supply to the transmission. So if there is a problem in either the Priority Valve or if there is excessive internal leakage in the steering/brake system there will not be enough oil flow/pressure for the transmission to operate correctly. You have plenty of pressure at the pump and not enough in the transmission so the conclusion is that it is leaking somewhere. Here is a link to a thread regarding a D4H where Mark250 explains how to make a blanking plate to block the oil flow to the steering & brake system so that potential internal oil leakages in the steering/brake circuit can be eliminated for testing purposes. I must point out that the D4H was suffering from a different problem to yours. However there is a lot of information about system operation, etc, that applies equally to your D5H. HeavyEquipmentForums
My apologies. I forgot to include the System Operation document.
Thank you for the information. Agree on the leaks and the priority valve. That's why I measured the pressure (A). I'll let you know in a few days what I found. Thanks also for the link to CAT D4H.
Hey nige, i would just like to ask what oil should i use for my D5H dozer? My mechanic is not sure if we should use 15W40 or Oil 90. Thank you
The correct answer is - none of the above. You should use an SAE 30 oil that meets Caterpillar TO-4 specification.
This may be irrelevant, but, on my 8PB D4H, the center pedal needle bearings gave up, leaving me a pedal that wasn't fully rising. This gave me a machine that performed normal cold, and got progressively lazier as it warmed.
"id just like to confirm that that right oil for transmission and steering would be SAE oil? My mechanic and i were confused on what to put since the transmission has gears and clutch linings." I'm sorry there is no such thing as an "SAE oil". The SAE is a standards institution that produces a scale of oil viscosities. This is where the expressions "SAE30" or "SAE15W/40" come from. SAE has nothing at all to do with an OIL TYPE . As you said the transmission and finals contain both gears and friction materials. The Caterpillar TO-4 oil specification was specifically developed for this type of power train component containing either gears or friction materials, or in some cases both. So for your transmission/final drives what you need is:- 1. An oil whose formulation/additive package meets the Caterpillar TO-4 specification. 2. An oil with a viscosity of SAE30 in the case of the transmission and SAE50 in the case of the final drives. Something like THIS ........ (Other brands are available).