Hello! My wheel loader lost traction, when it needs power. Before wheels were spinning on any ground, now in full accelaration, wheels do not spin anymore... What can be wrong before openning the transmition? Oil level is ok. Thanks for professional advice! Gerry
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You are providing a pretty limited description of what is happening. A serial number might help. Is the transmission overheating? What is the condition of the tires? How old and how many hours are on the machine. Have there been any repairs done to the machine recently? Are there any fault codes indicated on the monitor panel? What is the machine being used for, load and carry, loading pit run, charging a processing plant or loading trucks?
One more question.. is it blowing black smoke? Or any smoke? That gen cat has a fuel filter that dosent take much junk to plug it up.. mostly though need more info to give thoughts..
When I was in the trade a loader hand spinning tires would get his azz bit and if he kept it up he was down the road kickin' a horse apple. Mike
hello John and Daro, thanks for answers. Machine Id. is AAN00536. Transmission´s temperature is ok. Torque coverter oil level I checked and it is also ok, when machine is running, the oil stays between the range. Converters oil filter I also changed, but not with Caterpillar´s brand, just put a lower quality oil filter, I don´t know, if it matters anyhow? About hours I can´t say, it shows 3500 hours, but that is not real, machine has more hours. The machine I use on our farm, it does all kind of works. I noticed low traction at full accelaration, when I tried to push a tree over... I would like to know, if there is any ajustment at the torque converter´s oil pump to provide more power to the transmission with less accellaration? The engine is ok, no smoke at all. Thanks for your replies! Gerry
Do you have a tachometer, and is the engine running as full speed when it the machine stops moving? or does the engine slow down?
hello Delmer, the engine keeps full rpm, no slow down.
Have you checked the fuel system on the engine to make sure it is getting all the fuel it needs. No smoke can also mean not enough fuel is getting to the engine.
Thanks, I'm guessing John didn't see your response. One more thing before we say the torque converter and/or transmission is slipping. Does the machine slow down more than it used to when loading something more normal, like sand or gravel? When pushing a tree, especially if you have the bucket high for leverage on the stump, the angle will put more weight on the wheels to it won't spin the tires like it would pushing at ground level. You're probably looking at a bad torque converter or transmission, but I don't know what to tell you about those, and just wanted to get the other possibilities out of the way. As far as I know, there are no adjustments that will fix this, but there are pressure tests that should be done before taking it apart.
Hello, another doubt came to my mind. Does the Caterpillar 924G, year 2000, has an intelligent power distribribution control, so that the power is directed where it is momentaneously more needed, like the boom, steering, transmission? I ask, because the hydraulic oil hose from the steering was not tight enough and the main oil reservoir behind the cabine is under level. Could that be interfering the torque converter? Thanks for helps! Gerry
olá, tenho um carregador 924G que está tirando meu sono. máquina fria, tenho pressão de bomba de 300 psi em marcha lenta. pressão p1 - p2 - p3 abaixo do especificado. após 20 minutos de trabalho, a pressão da bomba cai para 80 psi. máquina perde toda a potência na transmissão. abrimos e trocamos todos os selos e consertamos a bomba. Não sei mais o que olhar. alguma dica?
hello, I have a 924G loader that is taking my sleep. cold machine I have 300psi pump pressure at idle. p1 - p2 - p3 pressure below specified. after 20 minutes work, pump pressure drops to 80psi. machine loses all power in transmission. we open and change all seals and repair the pump. I don't know what else to look at. any tips?
Attached is the System Operation document for the power train of your 924G. Have you checked the operation of the flow control valve #1 and the differential pressure relief valve #3.? Se adjunta el documento de operación del sistema para el tren de potencia de su 924G. ¿Ha revisado el funcionamiento de la válvula de control de flujo #1 y la válvula de alivio de presión diferencial #3?
Here is the location of the Flow Control Valve. Aquí está la ubicación de la válvula de control de flujo.
And here is the location of the differential pressure relief valve. Y aquí está la ubicación de la válvula de alivio de presión diferencial.
hello nige, how are you? I disassembled the valve group to see if I saw anything strange. I have no experience. apparently no scratches or damaged parts. From the posted image, is the flow valve located on the transmission housing?
Yes it is. The transmission control valve has to be removed to gain access to it.
ok i will remove and update you on that
Before you do, what oil are you using in it.? If you are using SAE30 TO-4 then put some 50 in it. Does it change the symptoms.?
I am using oil sae 50. with a manometer I observed that in all forward or reverse gears. When I shift into gear the oil pressure fluctuates and drops a few psi. I think this rules out the possibility of packet leakage. another interesting thing, I suspected some solenoid arming when it shouldn't. I turned off solenoids of 1st gear 3-4. I left only solenoid 4 on. when I give command for 1 gear, pressure drops close to 80psi and rises to 270 psi, even though only 1 solenoid is on. obs measurement of pressure in the transmission filter.
Yesterday I did a test that another friend asked for, I plugged the filter outlet to measure the pressure of the pump only. but my relief valve wasn't working and it blew the filter. I'm switching today. and I'm going to remove the valve control to check the valves
If the pressure dips and recovers like that then the chances are that clutch piston seals are leaking. Usually this becomes more pronounced as the oil heats up. A split-second flicker of the pressure gauge needle (maybe a fall of 50psi or less) would be a normal response to a gear shift, as one clutch drains and another one fills. However anything longer than that to recover the pressure on the gauge is a strong indication that there could be piston seal leakage. How many total hours on the machine.? Has the transmission ever been overhauled before.?
Revisamos a transmissão em busca desse defeito e o problema persistiu. Todos os selos foram substituídos. máquina tem apenas cerca de 10 horas, após revisão
We reviewed the transmission for this defect, and the problem persisted. All seals have been replaced. machine has only about 10 hours, after overhaul
for me to remove the next valve, and just pull it out? with a magnet maybe? I pressed it with my finger and it didn't move.
Give it a good whack with a hammer using a piece of wood or brass on the end of the valve. #65 shown as being part of the valve is an O-Ring, you will need to jar the assembly loose. Once it is loose maybe a magnet will pull it out.
This position is very difficult to get. in this part that I'm marking do I hit? will he come in? and take out a washer lock?
Yes. If you hit that it ought to almost "bounce" and should pop the valve out of the transmission case.
Did you check the screen orifice in the valve body to see if it’s plugged.
I managed to take the valve out, I blew from behind and it didn't seal air.
yes, before touching the valves that master nige asked
I would suggest to replace that valve complete. If I am correct there are no spare parts for it anyway. Also a question: You mentioned the variations of P2 pressure when shifting. Did you also have a gauge measuring P1 pressure at the same time.? The reason I ask is that the valve in your photo is called the "differential pressure valve" for a reason. It is designed to maintain the specified 50+/-5psi differential between P1 & P2 pressures in the transmission. So if the measurements of P1 versus P2 are oscillating a lot and the difference between them is consistently outside the specified range of 45-55psi that also points the finger of suspicion toward a problem in the differential pressure valve.
wanted to remove a flow control valve, did you disassemble it to check the oring? Or is there another way to test?
I only have a watch. one scales 0-800 psi and the other 0-450 psi. I made some cold vs hot machine comparisons pressure p1 cold machine in neutral at idle 120 psi. I engaged 1 forward gear without accelerating 100psi pressure p1 hot machine in neutral at idle 60 psi. I engaged 1 forward gear without accelerating 50 psi pressure p2 cold machine in neutral at idle 220 psi. I engaged 1 forward gear without accelerating 160 psi pressure p2 hot machine in neutral at idle 40 psi. I engaged 1 forward gear without accelerating 10psi
I noticed too. pressure p3 with hot machine 0 psi, I tightened the valve with a point and a cry of oil came out. however the torque converter output valve was giving 40 psi. how can you have output pressure and have 0 input pressure?
I cannot understand how P1 can be less than P2....??? P1 is to all intents & purposes transmission pump pressure. Are you sure that you are connected to the correct test ports.? See the attachment.
my manual confused me. I think I'll mount it again tomorrow and make new measurements based on your manual. I disassembled the differential pressure valve and managed to polish it, it sealed the air. I will try to assemble and measure
cold machine pressure P1 idle pressure 220psi Pressure p1 fast gear 320 psi Pressure p2 idle 200 psi Pressure p2 fast gear 295psi Pressure p3 idle 40psi Pressure p3 fast gear 90psi Torque converter output pressure idle 0 psi High speed torque converter output pressure 40 psi Measurements made with a 1000 psi manometer. Perhaps these values vary because it is not such an exact scale. My 450 psi gauge broke
I also measured at the transmission filter tap. I noticed something strange, I made a video but I can't post it. I will try to explain. When I turn on the machine, my pressure gauge reads 320 psi. when touching the accelerator and the rpm returns to idle, it drops to 240 psi. I turn the machine off and on and it goes back to dialing its 320 at idle. as if some valve opened and could not seal again.
I am a bit confused with the measurements. Measure the converter inlet pressure at high engine rpm with oil cold. That is the only value that matters. Then warm up the transmission to normal operating temperature. Measure converter out pressure with the brakes applied, transmission in 4th speed forward, and the throttle at maximum. Measure P1 & P2 under the same conditions as you measure converter out pressure.
Pressure p3 cold machine 90-95 psi 20 psi in 4 gear revving everything on converter output P1 accelerated all in 4 gears +-20 psi P2 accelerated all in 4th gear not even the pressure gauge pointer
So converter out pressure is only 20psi with the machine hot and the converter stalled.? Looking at your mesurements of converter out, P1, & P2 with the machine hot I think your problem is in the pump. I know you said at the start that you "repaired" the pump but it appears to me that it is losing efficiency when the oil heats up.
É justo, quando faço a medição antes da transmissão, não filtro a pressão quente e a temperatura oscila mais de 200 psi. e o frio também está abaixo do padrão, o que seria acima de 300 psi correto? ela marca fria 240psi.
Fair enough, when I take the measurement before the transmission, I don't filter the hot pressure and the temperature fluctuates more than 200 psi. and cold is also below the standard, which would be above 300 psi correct? she cold marks 240psi.
That was what I was saying. Even when the oil is cold the pressure never reaches the specification. When the oil is hot the pressure is even lower. That suggests a pump problem to me. It is even more obvious when the engine is idling. The specification for P1 at Low Idle is the same as for High Idle (310 ± 20 psi) but you are only seeing 220psi which is almost 100psi below the specification. This again points to the pump in my opinion.
Is there any way to evaluate the pump after disassembling it? or just changing it? There is a relief valve on the head of the lubricating filter, could it also nullify the pressure of the pump?
Good afternoon. I'm having a problem similar to Bruno97's. My machine is a CAT 924G, AAN series, number 917. This machine had a small fire that mainly affected the engine, but only damaged some hoses and wires. However, when I put the machine to work, after a few minutes it stopped moving, both forward and backward. We noticed that the transmission pump makes a different noise than normal and the pump's outlet hose is vibrating. Even with the machine in neutral, within seconds the transmission pump's outlet hose gets hot, and the transmission radiator's inlet and outlet hoses are also hot. When measuring the pressures at P1 and P2, the values were below the manual. P3 showed a value of zero. When measuring the pressure at the transmission filter, the value was also below the expected value. The strange thing is that when the machine is cold, it runs and has a lot of power at the wheels, but the system is overheating and then the transmission stops. We removed the transmission pump and didn't see anything abnormal regarding wear, however there was a threaded hole with nothing connected, which gives me the impression that air could enter the system (as shown in the photo). We also removed the flow control valve and everything seemed normal. I'm a bit lost as to what it could be. Is there a screw in the pump hole?
I would need to look at the parts diagram of the pump but I think that could possibly be what is known as a “weep hole”, designed as a tell-tale indicator for internal oil leakage past the seals in the pump. I will take a look but it will be a couple of days before I have the opportunity to confirm that theory. Have you removed the suction screen from the transmission case to check for any particles in it.? That would be my first suggestion because equipment fires can produce strange effects. Was the location of the fire anywhere close to the transmission.?
I don’t see threads, looks like a weep hole for the HP seal.
HarleyHappy, It's not visible in the photo, but there is a thread in that hole. Nige, we've already checked the magnetic filter and it's clean. We were told that the fire started near the transmission filter (we imagine it may have started in the parking brake), but the biggest damage was to the engine. The material the machine was working with caused particles to fall all over the machine and is highly flammable.
If you have eliminated that possibility then the next possibility to eliminate is that the pump is sucking air from somewhere inside the transmission case. In your photo I see a large quantity of liquid gasket material. Were all the O-Rings on the pump suction side replaced when it was removed for inspection.? Is there a suction tube inside the transmission case.? If so has it been checked for any holes/damage.? Do you have any photos of the internal parts of the pump.? Again I must apologise for not being able to post up parts diagrams but I have no connection where I am right now.
Here is the sectional view of the pump. There is no hole (threaded or otherwise) or plug shown in the pump body. From your photo I have arrowed the area where I think the hole is in your pump. The only thing I can suggest is to disassemble the pump far enough to determine whether the hole in your photo is blind or if it goes all the way into a chamber in the pump.
Just to give you an update: the transmission pump really does have that hole for lubrication. In the end, the issue with my machine was electrical—it was just being masked by the transmission pump. Thank you to everyone who helped me.
Can you give more details regarding what the problem actually was please.?