Have a 1996 cat 938f. Will not go forward or reverse... fluid level good, stored code ( 081-164f01 ) low voltage to electric transmission control... located electric trans controller has 24 volt and ground to pin 1&2. No low voltage.... trans nutrilizer switch is working, parking brake switch is working, each gear forward and reverse will result in 24 volt out of the controller to the solenoid... can anyone help me?
What is the serial number? Have you inspected the trans filter for signs of failure? You should be able to test trans pump pressure at filter housing.
Mobiltech got there while I was typing. Start with a Serial Number..... When was the transmission oil & filter last changed.? Does the oil smell burned.? Have you changed the filter and cut the old one open to look for particles.? Confirm that your Diagnostic Code is not Active.
Do you know what the pressure should be??
Fluid is in good condition. I will cut open the filter tomorrow morning and see if there is any metal
Not for certain without a Serial Number to look up the specs. Somewhere around 400psi though.
You should also be looking for small black particles with the appearance of sand. This would be burned transmission clutch material. Question: Did the "no movement F or R" happen suddenly or has the machine been presenting symptoms of random no movement for a while and now it has reached the point where it won't move at all.?
1km01626 is serial number... this happened out of nowhere... something I just noticed. When you move The shift handle, you can feel the machine clock into gear, but it will only inch up. Will also click forward when you put it in reverse? Question: Did the "no movement F or R" happen suddenly or has the machine been presenting symptoms of random no movement for a while and now it has reached the point where it won't move at all.?
When you turn on the key and the panel does its self-test you should see a SERV CODE light in the message window under all the warning lights. Does that light go out when the panel test is complete or does it stay on.? Based on Serial Number the transmission clutch pressure should be 275+/-25psi at test point A with the engine at High Idle. It should not change much if you drop the RPM to Low Idle. Then at test point B you should measure 42+/-10psi MORE than whatever you measured at test point A.
teat point a is 0 psi, test point b is 75 psi, test point c is 0 psi
I am going to take a guess and say the screened orifice in the valve body is plugged not allowing the pressure to modulate up above initial pressure.
do you know where it is located?
It is in the main valve body on top of the transmission. Some of them come apart inside or get plugged. It won’t allow the trans pressure to rise up to full engagement if it’s plugged.
I'm going to suggest a couple of other basic checks before you dig into the control valve, simply to eliminate other possibilities. 1. When you last changed the transmission oil & filter, did you remove and clean the magnetic suction screen in the transmission case.? If you didn't I suggest that should be your first step. Please post photos of whatever you find in it. You will have to drain the oil down somewhat (or completely) before removing the outer cover or you will get showered with oil. 2. Cut the transmission filter and inspect for either sand-like or metal particles. You said you were planning on doing that but didn't say if you ever did. 3. There is an orifice plug in the transmission dump valve. See the attachment. The complete valve is shown as #20 on Page 1. Go to #13 on Page 6 for the exact location of the plug. I've also included the Disassembly Procedure for the transmission control valve, the part relating to the dump valve is on Pages 2-4. If the orifice is plugged I suggest that you replace it, along with all the O-Rings, gaskets, etc, that are disturbed during the removal. NOTE: To remove the complete transmission control valve from the machine requires the cab to be removed AFAIK. However because the dump valve is relatively small it can be removed from the transmission control valve without disturbing the control valve itself.
I tested pressure at the port next to the transmission filter, I am getting 400 psi at 1800 rpm.... the dump valve orifis is in good condition. Everything looked pretty clean.. the filter had sludge and some small particles in it but nothing that looked crazy
The screen I am talking about is a 7t8803. Located in the main valve. It can be accessed without removing cab. Number 13 in picture. .
okay, I will take that apart now. Do you have to take off plug 16?
I think you have to take the plug out on the opposite side . I would take out both.
Have a look on Page 4 of "Vlv Gp - Trans Ctrl" attachment in post #14 above. The illustration shows both ends of the valve, not just the plug at one end. You can find the instructions for disassembly of that section of the control valve in Step 20 on Page 6 of the disassembly instructions attached above.
Okay, so called in a dealer CAT mechanic, he came out and did all the same tests I had already done and a said that he thought the transmission was junk and didn’t want to go farther. He said to lowboy it into dealer and have them rebuild transmission.. I can not comprehend that it needs a rebuild, it has 400 psi out of the pump, yet nothing at directional clutch/speed clutch. I took the valve body off the trans, I am going to take it apart tomorrow. Something I noticed just inspecting it, some of the pistons in the valve body seem to be just free floating, wobbling around. I haven’t taken it apart yet to inspect but is this normal?
Without seeing the movement you are looking at first-hand it's hard to tell. Attached the specifications for the control valve which may help you. Broken spring maybe.?
Did you ever get this loader going? If so what did it end up being?