CAT D4H LGP Transmission not engaging - overheating

1987 Cat D4H LGP w/ power shift transmission

Crawler runs great. As the transmission warms up, at about 210F, it tops wanting to go into gear. Very frustrating as you can sit there (for what seems like hours) fiddling with controls until it engages. In frustration, you will leave the machine to cool off and come back later. Recently just moved it down to another field and the tranny temperature did go up to about 240F suggesting if I kept going it would keep getting hotter.

Looking at oil level when cold, it shows full. When I looked at it hot, it showed low. Ended up dumping 5 gallons of Cat tranny fluid before it showed full when hot, but now shows way over filled on the cold side. Also changed the oil filter. Neither changing the filter or adding fluid has made any difference. Water temperature remains cool (~180).

Any ideas or suggestions?

Thanx

I am sure N.C. Wayne will offer more insight than I but here is what is probably happening . One of two things but most likely the charge pump for the transmission is weak. A weak pump will pump cold or cool oil but as the oil heats the efficiency of the pump goes down. That transmission has safety built in it so that when the pressure drops it will not shift or take gear, that is to keep you from burning up the transmission plates. You are running it and as the pump begins to get week you have slippage which increase the oil temp and also cause the pump to not put out as much. Big thing is longer you run it like the more expensive the repair. Might as well look at the torque convertor while you have the transmission out. Thirty year old dozer, unless you can do the work yourself going to be an expensive repair at the cat shop.

Ohio Machinery told me 4000 hrs. + - is the reasonable life expectancy for that pump.

Geez, was hoping something simple. Doesn't sound like an afternoon job.
Know where I can find the service pages by chance ((tranny 1CE01723)?

Which service manual do I need to figure out how to replace the charge pump:

Specifications, System operation, Testing & adjusting, schematics

or

Disassembly ans Assembly

Thanx

My comment may not help you except for some hope... a friend of mine had the same problem with his D4H. He called out the service guy several times... in the end it was a relatively inexpensive fix to his relief. Unfortunately my friend has passed away and I can't get any more details... just don't give up too quick. Get good help from a well experienced mechanic that primarily is helpful and not out looking for deep pocket money.

Unfortunately here in the boonies "experienced mechanic" are far and few between. Woulf have to have CAT to come out for a service call, 108 mi one way, would be rather expensive to just start. Kind of on my own - thus looking for some help and guidance.

(quoted from post at 16:50:08 08/28/17) Which service manual do I need to figure out how to replace the charge pump:

Specifications, System operation, Testing & adjusting, schematics

or

Disassembly ans Assembly

Thanx

Click to expand...

The disassembly and assembly section would be what you need. You can find the complete service manual on Ebay.

https://www.ebay.com/sch/i.html?_from=R40&_trksid=p2380057.m570.l1313.TR11.TRC1.A0.H0.Xd4h+service+manual.TRS0&_nkw=d4h+service+manual&_sacat=0

It will have all the sections in it.

Thanx. Think I am going to have to invest in a Service Manual either now or in the future anyway.
Found an ex-CAT mechanic in the area and might contact him to see how much he wants to take a look

I wrote the following for a similar D4H powertrain issue a few years back - perhaps it may help you:
Does the Powertrain get overheated quickly/easily now as compared to when new?

Presume you have changed Trans Filters, use the correct viscosity oil for the temperature range you operate in, checked screens on Powertrain sump, and checked the flex hose going to powertrain pump for collapsing/restriction?

If so, I'd suggest getting someone very familiar with a D4H to do an overall pressure test on the Powertrain Hydraulic System. Its covered pretty well in the Service manual which also has the Specified Pressure levels, but a few memories below:

The slamming into gear indicates a non-modulated shift.

There is a slight bit of time in a trans shift as one speed is dropped out and another is engaged - -it should not get worse as Temperature gets hotter - - that situation indicates a Leak somewhere in the system, which gets more apparent as oil heats up and gets thinner (reduced viscosity).

In the D4H, the Steering Clutches and Brakes get Priority on Oil pressure & Flow, then Trans P1 (Speed Clutch) and P2 (Trans Directional) Clutch.

The LH & RH Steer Clutches are Pressure Applied, and LH & RH Brakes are Pressure Released / Spring Applied, thus when you are dozing, all 4 are pressurized all the time.

In a Transmission shift, either to change Speed or Direction:
1) The Steering clutches and Brakes always stay applied and get their Oil First!
2) The Trans P1 Speed Clutch fills first, then
3) The Trans P2 Direction Clutch fills.

IF ANY CLUTCH or BRAKE Piston Seals, or the Parking Brake Valve (Which dumps Brake supply oil to both spring applied brakes to engage them) are leaking, the trans engagement will be delayed. It will get worse as oil temp rises.

The best way to Find a Leak is by a pressure test done at Engine Low Idle (NOT HIGH IDLE!!)speed with Warmed-up Powertrain oil.

Install gages on all 5 steer valve ports (Supply, LH Clutch, LH Brake, RH Brake, RH Clutch), Trans P1 & P2, and the Pump Port (I think its also on rear of trans cover).

With Machine parked in an open area away from all people and machines, Powertrain Oil Warmed up, and Engine at Low Idle, Watch all gages as the following steps are done - you are essentially "cutting off" functions one-by-one so that the Leak is cut off - which will show itself by the remaining gages going UP in pressure.

1) move the Parking Brake lever from Parked to the Run position and back - - gages may flicker as Park Lever moved but should not change high level.

2) Watch Trans P1 as you slowly move each Steer Lever back through Clutch, then Brake - you are shutting off flow to each clutch/brake piston as you do this - and IF P1 Goes up, you have just shut off the LEAK and need to fix that component.

3) At Engine Low Idle, with Park Brake Released, and foot applied Service Brake APPLIED, shift trans through and pause for a few seconds in 1F, 2F, 3F, Neutral, 1R,2R, 3R - again, if Trans P2 varies more than 10-20 psi in any of these gears, it indicates a leak in a Trans Speed or Direction Clutch.

If a "leaker" is found, fix that component.

If Pump Pressure is low and stays low, it may indicate a worn pump or a partially blocked oil sump hose/tube.

And, at 6000 hours, it simply may be time for a trans/torque convertor overhaul.

Best Wishes!
John

Thanx for the long post, helpful but not sure relevant.
Needed to order some gauges so in the meantime ran dozer until tranny fluid warmned up and then quit. Dozer is now stuck in the woods and does not move.
Pump pressure at startup. 100psi. Shift into gear. Driveshaft under floorplate stops moving, pressure drops to 0.
Pulling tranny pump this weekend.

Have a look at the forum at the link below.
AJ
Cat D4H Trans

What do you think about the CTP (turkey) vs CGR (italy)aftermarket pumps?
Big price difference. CTP - 6 mo warranty; CGR - 1 yr warranty.

Are the blue marks on the inside of the transmission pump suggest excessive heat due to lack of oil or something? Is this indicative of pump failure?

I can't see anything wrong with that and would put it back, going by that even though I cannot see the other parts but I would say there is nothing wrong with the pump,usually oil heating is a friction reason,ie clutch slipping or bearing binding,a smell of the oil,have you cleaned out the belly pans and made sure there is none of the plumbing damaged,is the shift lever jumping back to neutral when you try to select a gear?.
AJ

Not going to put it back.
Pump pressure is at 100psi at idle and 0 psi engaged.
No, does not jump out of gear, drive shaft stops turning, and engine under strain (black smoke).
I dont think pump should have burn marks.

Hope the new pump solves your problem,I would say that blue dis-colouring is due to the heat treatment at the factory,as I am a city dweller now dozers are rare and I am not familiar with yours,the older dozers should the charge pressure be low the select lever would jump back to neutral as soon as you took your hand away,the problem of the engine bogging down means there is a mechanical blockage of the power train,my guess would be that a clutch disc has broken up and got sandwiched between two others keep them engaged at all times,say for instance that was happening in forward and you select reverse,the engine would bog down and the machine lose power reversing,the oil would heat up very quickly,I can see no reason for a worn oil pump to cause the engine to bog,the brakes are releasing ok?.
AJ

Well that was a waste of time and $1,000,00. The new pump puts out less pressure than the old one.
Old pump: 100 psi at idle, 0 psi engaged
New Pump: 50 psi at idle, 0 psi engaged
A machinist friend of mine says unequivically that the blue marks are machining dye.

Lets review situation - may be a related or separate issues.
Original issue: Transmission would not go into gear after trasnmission warms up, greater than 180-190F. Otherwise worked normally.
Current issue: Transmission engages (transmission cold) but does not move. Increasing idle causse engine to load (black smoke).
Drive Shaft: Spins freely in neutral, stops spinning in gear (F or R)
Pressure: Transmission charge pump: 75psi at in neutral, 0 psi tranny engaged (new pump)
Rear ports:
Lower port (rt side): 0 psi at idle, 300 psi gear engaged
High port (lt side): 250 psi at idle, 350 psi gear engaged
Any new thoughts?

With the price of parts you can't go on replacing everything that you think may be faulty,have a word with your Cat service manager and he will probably point you in the right direction,more than likely the trouble is in the transmission and like I said before it is probably a broken piece of disc that is jammed between two others,when that happens and another gear is selected the machine is in two gears at once and is more or less loaded up and the engine will bog down,by the engine bogging down means that the charge pump is ok,the torque is ok and the forward and reverse clutch,you know all that is working as it is responding to the lever,get the serviceman to have a look its your best bet before you buy more parts that will not cure the problem.
Good luck
AJ