Cat 120H Transmission

Hi, how are you doing? I have the running clearance specifications for the clutches — could someone tell me if this measurement should be taken with the clutch pack compressed or free?

This procedure should assist you in establishing the running cleanrance of any particular clutch. It is somewhat generic but in effect what you are measuriing in order to establish the running clearance of a transnmission clutch is the piston movement from the "resting" (released) position to the "applied" position

1. Position the shaft containing the clutch assembly in the vertical position. The end plate of the clutch being measured should face upward.
2. Make sure that the end plate (2) is free to move.
3. Position the tip of a dial indicator on the end plate and zero the dial indicator.
4. Apply air pressure of approximately 140 kPa (20 psi) to the appropriate passage in the shaft for the clutch that is being checked.
5. When air pressure is applied the end plate should move and contact the lock ring (3). When the end plate is in contact with the lock ring determine the distance that the end plate moved from the dial indicator readings. This measurement is the running clearance of the clutch pack.

What I find with these transmission is that the back of the pistons will wear down from spinning in the housing. They can also wear on the half moon retainers on the clutch backing plate. If you have clutch discs slipping out of place you probably have worn pistons.

WOW, following this thread is starting to give me an ulcer knowing I will probably be opening the tranny on my 120H. I guess I better stock up on antacid.

Jeez,these grader transmissions are some bit of trickery by the sounds of it. One here on a job yesterday. Looks fairly new. View attachment 347338

View attachment IMG_0656.jpeg

Good evening Did any one find the solution to the problem I'm having similar issue I have 12h with the 4er I don't have 2, 3,6 gear in forward no oil pressure in the test port it all indicates 2 clutch patch. I already tore down the transmission found the 2 clutch pack fine the reverse was tost the same as mentioned in the thread. We just installed everything and now reverse is stronger but can't find 2,3,6 gear all ready changed solenoids no change appreciate any help.

Please post a machine Serial Number so that the correct technical information can be found.

Good day 12H Serial # 4er00468

Thank you. Have you checked for power on the appropriate transmission solenoid when either 2nd, 3rd, or 6th speed FWD is selected.

Hi, I'm checking right now making sure that the right solenoid is connected to the right harness I think my problem is right there just looking for the electric diagram

Just checked all solenoids they are all connected in there right position and Energized in the correct way Y took the quick coupler off port C and I do have oil just not pressure it's leeking some place

Also changed solenoids and valve to a good working solenoid and it's the same problem

Omar Simental said: Hi, I'm checking right now making sure that the right solenoid is connected to the right harness I think my problem is right there just looking for the electric diagram Click to expand... I can help you with that. Check you message inbox.

Omar Simental said: Also changed solenoids and valve to a good working solenoid and it's the same problem Click to expand... Can you confirm that you changed the complete solenoid valve assembly including the cartridge as shown in the illustration below and not just the operating coil (Ref #1).?

When you disassembled the transmission as you mentioned in Post #27 above, did you pull the control valve assembly apart to perform a cleaning and inspection of all the internal parts.? Also, and this is extremely important to correctly identify parts, I need you to get the Serial Number from the transmission. The system does not identify it and there are no less than SEVEN possibilities. I don't want to start quoting Part Numbers only to find they are the wrong ones for your specific transmission

Hi, yes I changed the complete cartridge assembly and the one I took out is working fine in the other slot. I also took apart the control valve to clean checked the springs and cartridge everything looked good inspected for cracks or anything didn't find anything unusual I find it hard because I have oil in port C in the control box just not enough pressureas if it were leeking some were.

Thank for the electrical diagram, I couldn't find in cat sis the hydraulic diagram for the transmission to check at the end of the housing for pressure

Omar Simental said: I also took apart the control valve to clean checked the springs and cartridge everything looked good inspected for cracks or anything didn't find anything unusual Click to expand... When you disassembled the two main sections of the control valve did you remove and inspect/clean/replace the plastic screened orifices.? I'm not sure how many there are in your particular control valve. I still need the transmission Serial Number from your machine to look deeper into it. There was an update to the valve body for the selector & pressure control side of the transmission control valve because the previous version was prone to cracking which caused internal leaks and pressure loss. All 4ER-prefix 12H machines were built with the former version of that valve body. See the attached. Do you recall looking at this area.?

Trans serial # 4my05320 Arrangment # 1442234