140H Motor Grader, lost all reverse gears and forward 3,4,8.

Hello everyone, I’m looking for some advice on a Caterpillar 140H Motor Grader (S/N: 2ZK07046) with a transmission problem that has been difficult to diagnose. Initial symptoms The following gears had very little pulling power, even though they engaged normally: Forward: 3, 4, and 8 Reverse: 3 and 6 Repairs already carried out Removed and rebuilt the transmission. Replaced all clutch friction discs, seals, O-rings, and related components. Checked, tested, and even swapped the transmission solenoids. Reassembled the transmission correctly. The problem remained exactly the same. Further diagnosis We then performed pressure tests and suspected the transmission control valve because it appeared to have slight internal damage. We replaced the complete valve body. (161-7055) After replacing the valve body: Transmission pressure is now within specification. However, using the diagnostic tool we found fault codes 641-5 and 644-5. According to CAT SIS, these codes could be caused by the: ECM Solenoid Wiring harness Additional checks The affected solenoids have been tested and replaced. The wiring harness has been checked, and power supply and continuity appear to be correct. After these checks: Code 644-5 disappeared. Code 641-1 remains active. We have now lost all reverse gears, while the original forward gear problem (F3, F4, and F8) still exists. My questions Before I replace the transmission harness or purchase and configure a replacement ECM, I’d like to ask: Has anyone experienced a similar issue on a 2ZK-series 140H? Are there any common wiring faults, connectors, or grounds that should be checked before replacing the harness or ECM? Could there be another component causing both the persistent 641-1 fault and the loss of all reverse gears? Are there any additional tests you would recommend before replacing expensive components? Any advice or similar experiences would be greatly appreciated. Thank you in advance.

First a question. Early in the piece you quoted Active Codes 641-5 & 644-5. Later in the text the 641-5 becomes 641-1. Can you confirm the 641-X Code please. Nik3002 said: Additional checks The affected solenoids have been tested and replaced. The wiring harness has been checked, and power supply and continuity appear to be correct. Click to expand... Next a comment regarding testing the harness. The wires you are testing power 24V solenoids therefore carry a fair bit of juice. A continuity check will not conclusively prove that any wire in the harness is good. What I always suggest is to disconnect all the relevant wires at both ends (ECM & solenoid). You have SIS so look on the electrical schematic RENR1434 for all the intermediate harness connectors that are between the transmission ECM and the solenoids and divide it into sections. This will make it easier to troubleshoot. I see CONN 2 and CONN 45. To test any individual wire jumper one end of it to the machine frame as ground then use a 5A fused test light connected to batt+ and apply it to the other end of the wire. If any wire will pass 5A consider it as being good. There is a short wiring harness 147-1771 (#8 on the illustration below) mounted on a metal frame that often goes hard because of heat and deteriorates. I suggest you check that one first. Regarding your loss of certain transmission gears I think you should be concerned with the operation of only two clutches: - 3F, 4F, & 8F is something involving clutch #5. Missing all reverse gears is clutch #3. A question regarding the replacement 161-7055 valve body. Did you transfer all the internal parts from the former to the new valve body or did you replace anything else with new.? At least all the O-Rings inside both sections of the control valve. If you did not fit all new parts did you at least replace all of the orifices inside both it and the other half of the control valve.? You will find them on the attachment that I did for a transmission rebuild a long time ago. I recall there being quite a few of them. Generally when a transmission has a clutch failure the particles tend to block those orifices and affect transmission operation. Experience has shown that it is difficult to clean them, better to replace.

Apologies for the typing error, 641-5 was always the correct code. 644-5 has since cleared; only 641-5 remains active. On the harness testing i will ask an electrician to carryout proper testing On the control valve — all new O-rings were fitted. During the previous teardown, the bore inside the valve body showed signs of slight chipping which we believe caused the pressure loss on clutch #5. As a result the TC relief valve spool (9U-8668) was also replaced as a precaution, and pressure was reset to spec. However, the orifices were not replaced they were cleaned but not swapped out, which based on your experience may need to be revisited.

Nik3002 said: Apologies for the typing error, 641-5 was always the correct code. 644-5 has since cleared; only 641-5 remains active. On the harness testing i will ask an electrician to carryout proper testing On the control valve — all new O-rings were fitted. During the previous teardown, the bore inside the valve body showed signs of slight chipping which we believe caused the pressure loss on clutch #5. As a result the TC relief valve spool (9U-8668) was also replaced as a precaution, and pressure was reset to spec. However, the orifices were not replaced they were cleaned but not swapped out, which based on your experience may need to be revisited. Click to expand... Regarding harness 147-1771 we had replaced 137-1120 (ordered for our other 140H, s/n 2ZK00916) and swapped across as a test, but the fault persisted. The two harnesses appear physically identical from google though without SIS access at the moment I can’t confirm if the harnesses are the same or two different.

Nik3002 said: Regarding harness 147-1771 we had replaced 137-1120 (ordered for our other 140H, s/n 2ZK00916) and swapped across as a test, but the fault persisted. The two harnesses appear physically identical from google though without SIS access at the moment I can’t confirm if the harnesses are the same or two different. Click to expand... 137-1120 is the basic harness. 147-1771 is the harness mounted on the steel ladder support - so you can rule that out. Nik3002 said: Apologies for the typing error, 641-5 was always the correct code. 644-5 has since cleared; only 641-5 remains active. Click to expand... Thanks for confirming that. I will try to find some troubleshooting procedures for the 641-5 Code and post them up. However I can confirm that it is a low current code for #1 clutch solenoid - which is not one of the two clutches that are causing the lack of specific FWD gears and all REV gears. It is definitely a Code caused by lack of current in the specific circuit. That is strange - are you sure everything is wired correctly at the transmission solenoid connectors.? Nik3002 said: On the control valve — all new O-rings were fitted. During the previous teardown, the bore inside the valve body showed signs of slight chipping which we believe caused the pressure loss on clutch #5. As a result the TC relief valve spool (9U-8668) was also replaced as a precaution, and pressure was reset to spec. However, the orifices were not replaced they were cleaned but not swapped out, which based on your experience may need to be revisited. Click to expand... If it was my transmission I would replace all the plastic orifices without a second thought and clean all the steel ones along with all new O-Rings on everything. If I had any doubt regarding a particular steel orifice I would replace that also.

Also while I think about it, have your electrician measure the resistance of all eight transmission solenoid assemblies and post up the results please. The specification is 31 ± 3 ohms. Note that the numbers of the clutches are not in a logical order. You have to be careful with this or you could find yourself working on the wrong clutch.

I have been looking more closely at the naming convention on the clutches. All the service documentation for your machine is different to what I posted above. See the illustration below. 641-5 indicates an open circuit for the FWD LOW clutch solenoid #1 (top right), Ref A. See the attachment. Ignore the fact that the component identifier is 1401 rather than 641. All the wire colours and the procedures listed are exactly the same. Use it in conjunction with the RENR1434 electrical schematic.

I think I would like to know what the shift control is telling the transmission

pittsburgh cat man said: I think I would like to know what the shift control is telling the transmission Click to expand... I wonder if it’s equipped with the updated shifter control. IIRC to install it required wiring changes. I’d need to look into that. EDIT: The new 640-7427 or 640-7428 transmission control applies to 2ZK-prefix machines from S/N 2392-Up. it does require wiring modifications to install. Which upgrade applies is dependent on the current control. Check whether or not the installed control is a 180-3531 or 253-4019. I suspect it will be one or the other.

Over the years I've seem the shift control do some strange things Had a dozer one time engage 3 clutches at one time. I could actually see it engaging 3 clutches on et

Thank you both for the input. I will look into the shifter control tomorrow along with carrying out the electrical tests as advised. Regarding the shift lever, it was replaced at some point in the past but I need to verify exactly which lever was fitted and whether any wiring changes were made at that time. I will confirm this tomorrow. Some additional background that may be relevant: Before the issues started, we called a technician to diagnose the machine. At that point there were no active fault codes showing, so the problem was assumed to be mechanical. We waited over a week for the replacement valve body to arrive. After fitting it, pressure readings are now on par with manufacturer specifications. One thing I am not fully confident about is whether the Cat ET diagnostic tool is reading the correct codes. The ET software and tool we are using is borrowed from a colleague and is an unofficial Chinese cracked version. I am not sure if this affects the accuracy of the fault codes being displayed. Also worth mentioning before we started the machine with the new valve body, the machine was washed thoroughly with a pressure washer. I suspect water may have gotten into connectors or wiring in unwanted areas. The washing was done a few days before we fired the machine up with the new valve body. This could potentially be causing some of the electrical faults we are seeing. With the same grader, previously this year the operator had caused a fire in the harness when replacing the starter motor, though i was absent at that moment to know how they tackled the issue but there were 2 harnesses which were replaced and one of them was modified with and it was fine and maybe until the pressure wash it might have caused the issue to arise. The harnesses replaced were: 139-0269 & 138-9116

The first thing we are thinking to do tomorrow is swap the control valve from the other 140H (s/n: 2zk00916) and check if the problem still persists with the grader. Since we have addresses almost all electrical issues will try first by swapping the control valve.

Nik3002 said: Regarding the shift lever, it was replaced at some point in the past but I need to verify exactly which lever was fitted and whether any wiring changes were made at that time. I will confirm this tomorrow. Click to expand... Please do. If you need any documentation regarding the wiring upgrade please ask. I located it a few minutes ago. Nik3002 said: With the same grader, previously this year the operator had caused a fire in the harness when replacing the starter motor, though i was absent at that moment to know how they tackled the issue but there were 2 harnesses which were replaced and one of them was modified with and it was fine and maybe until the pressure wash it might have caused the issue to arise. The harnesses replaced were: 139-0269 & 138-9116 Click to expand... One of those part numbers is the engine wiring harness, the other is the rear chassis harness. Neither of them contain any transmission control wiring. The two harnesses installed between the transmission control in the cab and the transmission control valve are 137-1721 (XMSN Control) and 137-1717 (Rear Frame/XMSN) Nik3002 said: One thing I am not fully confident about is whether the Cat ET diagnostic tool is reading the correct codes. The ET software and tool we are using is borrowed from a colleague and is an unofficial Chinese cracked version. I am not sure if this affects the accuracy of the fault codes being displayed. Click to expand... I don't think so. The screen shots (that I should have looked at earlier if I am being honest) seem pretty logical. If you like download a copy of the Product Status Report (PSR) and post it up. It will contain all the electronic data, Diagnostic Codes, Events, etc, for the complete machine. If you haven't done it before there are videos on YouTube. Just make sure that the PSR is downloaded in the optional Adobe pdf format otherwise it will not upload to this site.

I will try and get the PSR and run the electrical tests. Regarding the lever it was replaced a long time ago and it has not caused any problems but will make sure to ask and get back to you

Nik3002 said: I will try and get the PSR and run the electrical tests. Regarding the lever it was replaced a long time ago and it has not caused any problems but will make sure to ask and get back to you Click to expand... Get the Part Numbers of all the electrical/electronic components please, just to ensure everything that is currently installed will "play nicely" together. What you could also try is checking that ALL the solenoids for the relevant clutches are engaging at the correct time. Neutral engages 2 solenoids, for other transmission speed FWD & REV three solenoids are engaged. This can be done if the drive shaft is removed or raise the rear of the machine up until the rear wheels are off the ground then use blocking under the tandems. Back-probe into solenoid connectors to check if they are being powered.

This test was done and all solenoids were engaging if im not wrong but i shall confirm this with my colleagues. What we also observed is that when we adapted the pressure gauge and when clutch number 5 is engaged there is pressure reading so we know that the clutch was engaged but the gears (3,4,8) still fails. My other question was that if the initial pressure reading is abnormal what can be the outcome?

Nik3002 said: My other question was that if the initial pressure reading is abnormal what can be the outcome? Click to expand... Do you have the necessary plate to install between the control valve and the body of the transmission to permit the measurement of initial pressures.? If initial pressures are outside specification then maximum pressures will likely be similarly outside.

No, but we have called a technician for a proper pressure test tomorrow so im hoping to get answers for questions before the testing.

Nik3002 said: No, but we have called a technician for a proper pressure test tomorrow so I'm hoping to get answers for questions before the testing. Click to expand... If you don’t have the test plate all that can be measured is the maximum pressures. Please read the pressure testing procedure and under no circumstances let the technician fiddle with the adjusting screws if any clutch pressure is outside the tolerance permitted in the specifications. My suggestion would be to simply get the transmission up to normal operating temperature, check the pressure on each of the eight clutches, and report back with the results.

Good day sir, My colleagues followed the schematic and used the new harness to plug in solenoids into the control valve of the other 140H and installed it into this one with the problem. What happened initially was that when forward gears were engaged machine tires were turning backwards, and when engaginf reverse machine tires were moving forward. We are checking in SIS the correct wiring for the solenoids to this issue. After swapping a few i decided to use the et and it showed me 3 new codes and the previous ones were not active. The new codes are: 177-4 643-5 648-5