Hi there I am new to the forums. I have a CAterpillar IT24F wheel loader in my shop with major transmission problems. The machine serial # is 4NN00901 and the transmission serial # is 6YX04159 The transmission started slipping awhile back and progressively got worse to the point that the machine will barely move on my level parking lot. I drained the fluid from the transmission and checked the pickup strainer and it had quite a bit of very small dirt and wood chip particles in the filter. The spin on filter seemed relatively free of foreign material. I removed the transmission from the machine and disassembled it and found some more foreign material inside the bottom of the case and inside the control valve body and dump valve. I disassembled and checked all the clutch packs and tested them and no issues with them. I put the transmission back in and it still slipped really bad so I did a pressure check on the system and found I had low pressure. I got a new transmission pump from Caterpillar and installed it and I still have low transmission pressure. I removed the transmission again and disassembled it and disassembled the torque converter and found no issues with it. I need help figuring out why all my pressures are low. My pressures are listed below: Pump pressure is 100psi at idle and 275psi 100% THROTTLE at the filter P1 pressure is 75psi P2 pressure is 35 psi P3 pressure is 0 psi I have a cat service manual and it says pump pressure should be 310 at idle, p1 and p2 should be 300-350 and p3 should be 80 psi any help would be appreciated. Thanks
When you had the control valve apart did you check if the screened orifice was plugged?
Yes, ive had the valve body apart and pulled the screens out and cleaned them.. most of the dirt was around the dump valve, but there were no damaged spools/slugs or broken load springs and none of the spools were stuck in the valvebody. I have checked both converter relief valves, and the flow control valve. it really has me stumped at this point.
Get a brand new screened orifice, they sometimes break and turn inside causing trouble. From pressures you have no oil is getting behind the load piston. Later Bob
I checked all the screens again this morning and none of them are damaged/turned inside out or anything along those lines..
I had one screened orifice that had a little plastic stem inside that would move around and block the orifice. Check it real close or just change it to be safe. You have changed the spin on filter too I hope . If there is debris in the valve the filter is bypassing. Is the oil foamy or is there any pump noise like its sucking air somewhere. Possible suction line cracked.
Yes I will inspect them again and if it comes down to it they will be replaced. I did replace the spin on filter, and cleaned the suction screen in the bottom.. I also inspected the filter housing and bypass valve inside it and everything seems fine with it.. I'm thinking maybe someone didn't have the right fluid in it or the old filter was stopped up letting it bypass.. The pump is quiet and the fluid didn't appear to be foamy,, I have a new pump from cat on the machine, but it did the same exact thing as the original pump so I'm guessing it wasn't bad.. How can the pump actually suck air inside the transmission because their are no pickup hoses in it.. It only has an oring seal between the two halves of the case that seal the oil pickup passage.. It's just odd the charge pressure is only 100 at idle and 250 at 100% throttle.. I tested another identical machine and the pressure was 350 at idle.. And I have no pressure on the P3 test port for the converter..
Are you aware that the Screened Orifice is inside the trans valve pack? Later Bob
BOB, do you mean that the office is in the control valve body? If so then yes, but if you mean the clutch packs then no I didn't know that.. I had all the clutch packs apart and tested them with air pressure to see if they would engage and they did.. This is the first CAT transmission I've had apart but I've done many john deeres..
I take that back this is my second cat, I done a 924 wheel loader a couple years ago that built too much pressure up and blew the spin on filter off and blew the seals out of the clutch packs.
Yes that was the one I meant Strick, it's made of plastic and coloured to identify the orifice size. It controls modulation time from initial to full pressure, your trans is staying at initial pressure and not coming up. Take a good look at the valve around the load piston and see if there is a plug to remove for testing initial that has fallen out. Can't remember for sure but think there might be. Later Bob
Bob, Ive got the modulating relief valve out and took it apart,, the screened orfice is dark green colored,, it took a small hex head Allen wrench to thread it out.. When I look straight down thru the valve where u put the wrench on it there appears to be a small pin hole thru the plastic so I'm not sure if that's the hole your referring to or not,, I'm gonna order a new one from cat since it's only $20 and see if it looks different.
I have never seen one that threaded in, just pushed in with an oring on them. If it's plastic and can push in it will be the one. I hope you aren't referring to one of the screws plugging one of the holes in the load piston. I recall three holes drilled on a spiral around the load piston with two having plugs in them and one open. To be sure follow the oil path back from the load piston towards the pressure diff valve and you should find the orifice I mean, or check parts book if you have it. Later Bob
Bob, I have the parts manual and service manual.. According to my parts book, the load piston and the screened orfice are a part of the dump valve.. The load piston is 6Y-7582 and the orfice is 8E-6051.. My orfice threads in and is a dark red in color.. I assume we are talking about the same part, if u have a book maybe you can double check this is right,, my parts book clearly shows that the orfice has threads on it and an oring and a screen. The modulating relief valve also has a screened orfice in it.. I just want to clarify that we are talking about the same parts..
No that's not the one. The orifice we refer to is in the modulating spool and is part number 7T8803. It does screw in on these models.
You have a newer valve than I am familiar with, sorry about that. Later Bob
Well I got the new screened orfice from caterpillar this morning and compared it to the original one and it's pretty obvious now that the old orfice is broken as the end of it was broke/blew apart.. I hope this is all that is wrong with this transmission but it's hard for me to not be skeptical of whether or not that little orfice can be causing all my issues..
You need to get hold of all the blown apart pieces, one of then might be clogging up a small passage to the load piston. Can you post a pic of the old orifice please? Later Bob
Yes I will try
You should be able to tell which one is new and old as the new one is clean and shiny and you can see the bottom piece is missing out of the old one
Thanks that is very similar to what I recall but they just pushed in and had a plate on top to hold it in. Now to me it seems the orifice has blown out of the old one. I was concerned the orifice was clogged. Now if the part blown out is the orifice the trans should hard shift(snap into gear fast and jerk you in the seat) If you still are running on initial pressure some debris from the old orifice is clogging up the passage from the orifice to the load piston. The load piston is on the opposite end of the spring as the modulating relief valve is and after a shift clutches fill to initial pressure as yours does now. Oil pressure then comes through the orifice that controls the time of clutch fill and clutch building to full pressure. Later Bob
So just to be clear , we are talking about #13 in this picture?
That's an ICM trans by the look of the valve. Where is the trans ECM? in the shifter? I would also check the trans neutralizer switch and or wiring. A short or bad switch will neutralize the trans. If the ecm is in the shifter I have seen a bad alternator(overcharging) kick them out of gear and need recycling through neutral to drive again. Later Bob
Ironic you should bring this up a mechanic that used to work for the company I do pulled the control valve apart on an IT24 for this exact reason and after he gave up I got out to it, turned out it had a bad connection at the trans ECM fuse holder the entire time. Also had the over charging alt. Quite a few times.
Sorry I was away for awhile,, I got the transmission back in and it's working better than it has since I've had it.. Now all my pressures are correct and I have all the reverse gears and 4th forward gear.. It appears that a combination of the screen office and a bad deal around the suction screen cover were to blame for my low pressure issues.. However now the transmission tries to lock up when it's in forward gears 1, 2, 3 (forward low clutch).. I've changed the selector spool and solenoid and it hasn't helped.. It seems odd that when you engage the transmission in any gear 1-3 forward the machine will go forward 15-30 feet and lock up(almost as if it's trying to go into reverse at the same time).. I know it's not the service or park brake because I disconnected all the brakes and it doesn't do it in reverse or high forward.. I hope it's not something internal to the trans. Anyone have any thoughts??
I also forgot to mention that the neutralizer switch is working properly, and I'm unsure of where the ecm is exactly,, I think it's behind the seat because there is a rectangular looking computer with a large bundle of wires coming out of it.. There are no active codes stored and the charging voltage is 27 volts now but there was an inactive code stored for voltage being too high,, looks like it has a new alternator on it now..
Drive the machine and when it jams up shift to 4th, if it frees up the new clutch you activated is the one that's dragging. Also get it rolling in 4th then go to neutral and see if it keeps going free or starts dragging. Look to see what clutches are being used. Later Bob
Ok bob, I did what you said when I go from 4th to neutral the trans goes into neutral and quits pulling like normal.. When I go from 3rd to 4th the transmission quits dragging and works normally.. When I start in 1st and shift to 2nd when it drags you can tell it shifts but it still drags.. Shifting from 2nd to 3rd it feels like it is dragging very little at this time.. All reverse gears seem fine and 4th forward seems fine.. All pressures are within specification..it doesn't seem to shift too hard/quick not is it slow to engage.. Thanks again... Hopefully The issues get worked out soon because this machine is being a nightmare... It's been at my shop about 6 weeks.
You need to find the clutches used for each gear. One common to 4Th and reverse, pressure oil is leaking into it some how and making it drag. Was any clutch pack worn heavy? I don't know if it's a housing or the valve body. Later Bob
All the clutches/clutch packs looked good with no signs of wear so I didn't replace anything in them.. I blocked the machine up off the ground so all 4 tires can turn and engaged the machine in 1st gear and ran it until it stopped pulling/locked up.. When I unplug the solenoid for 2nd gear the transmission releases itself a but won't engage in any gears until the plug the solenoid back in.. I repeated the test to unplug 3rd gear and 4th gear solenoids individually and the machine done the exact same thing.. When i unplugged the reverse solenoid the transmission stayed locked up and would still engage in other gears so I'm guessing the problem isn't in the reverse pack.. The issue must be that the 3 forward gears are dragging against each other.. Hopefully this will shed some light on the issue.
When you unplug a solenoid it would shut down the trans computer(open solenoid fault) Try to take the coil off of the valve and then run the machine. This is going to be hard helping from a distance. It may not help on your machine but on another one that had a cracked clutch housing had a rise in lube pressure when oil leaked through the crack. Later Bob
Well now that you mentioned the cracked clutch pack I remember having the valve body assembly off the transmission and was doing an air test using 150psi to see if the clutch packs would engage and the reverse clutch pack tested ok with no leaks but when I put air into the oil port for the forward low clutch, there was some air leaking back out of the forward high clutch hole thru the trans case.. I didn't give it much thought because when I air tested the clutch packs out of the transmission I didn't notice the leak.. So more than likely if I have air pressure leaking between the forward low and high clutch then either my transmission case has a crack in the oil passage or the clutch pack shaft has a crack in the oil passage..
See if someone can check the valve out for you, the cheapest and easiest to change. Later Bob
I've been fighting this loader for like 6 months and still can't figure it out.. finally bought another good used transmission, but it didn't come with a valve body and I can't seem to find a good, used complete one..the loader is doing the exact same thing it was doing with the old transmission, so I'm guessing the transmission wasn't the issue.. I have a cat service manual and I've done all the electrical tests and troubleshooting but can't seem to figure it out,, there are no diagnostic codes active, all the wiring has been checked, new solenoid installed and everything passed the test,, all pressures are good, there is no trouble shooting in the manual for the symptoms my machine has.. I'm guessing maybe something cracked or faulty in the valve body?? I've had it apart a few times and can't find anything wrong.. Anyone have any ideas?