Ford 545C Transmission Lockup Not Working

Hi again Ford Fans. I have a Ford 545C loader tractor I bought this last fall that has a transmission problem that I can't find source. It is the 3 cylinder diesel with an 8 speed electric solenoid shuttle shift with the torque converter lock up feature. the transmission works fine through all the gears in forward and reverse. It is smooth operation with no perceivable slippage but the lockup clutch in the torque converter will not function when the button on the end of the shuttle shifter is pressed. When the transmission is in any forward position and the green lockup light is illuminated nothing happens. I went so far as remove the loader to get at the lockup valve on the right side of the bell housing area. I removed the valve and bench tested it with 12 volts to the solenoid and it cycles great and when I applied air to the center port it directed the flow to the lower port when energized. To further check the electrical circuit I put a node light to the solenoid connector it will illuminate 3 to 5 seconds after the lockup dash light comes on so the modulator is working correctly. The coil in the solenoid has 8 ohms of resistance as per the service manual. After reinstalling the valve and changing the transmission oil and filter it still does not lock up. I have another one of these tractors that works fine. It is a 445D 4WD with the same transmission I used as a comparison. I started it and put it in 5th gear and placed the shuttle in forward position while holding the brakes at a little over idle where I could tell it was slipping through the converter. While holding the brakes I engage the lockup and when it engages it will almost instantly kill the engine just like dumping the clutch on a manual tractor at low engine speeds. That's the only way I know of testing it short of running it in a higher gear down the road and waiting for it to power shift into the lockup position. To cold right now to try that so when I apply my same test to the 545 it will start to pull in any forward position but nothing when the lockup position is selected even though the dash indicator comes on immediately when the button is pushed and I wait the five or so seconds for the solenoid to cycle. I've done as much testing as know and am reasonably sure the problem is not electrical or the lockup valve assembly. While I had the access cover off and the valve removed and reinstalled I can see the rear of the torque converter and it looks new or rebuilt but I have no way to tell as I don't know the tractor history. And after studying the service manual I could find no way to test the operation of the lockup hydraulic system or take any pressure readings other than on the shuttle valve. Can anyone out in Ford country advise me if there are any tests for the torque converter/lock up clutch short of spitting the tractor and taking it to a transmission rebuilder for service. One final thought, if the torque converter has been replaced is it possible to put in the wrong one from the 4x4 shuttle without the lockup clutch, Don't know if it will fit and work just no lockup even though it has the valve and oil passages.
One final thought, if the torque converter has been replaced is it possible to put in the wrong one from the 4x4 shuttle without the lockup clutch, Don't know if it will fit and work just no lockup even though it has the valve and oil passages.

You explained your problem well. Unfortunately I don't know much about the 8x8-s. From a review of the online parts pages, to the extent the parts are described, it may be that the difference between the 4x4 and 8x8 is the lockup valve on the side of the oil distributor, the harness extension thereto and the converter. The rest of the parts appear to be the same. You may be able to see a physical difference between the converter on your D and the converter on your C. Otherwise, the sad answer to your dilemma is yes, someone probably installed the cheaper non locking converter in your C and it fits perfectly. If this is so, then you need a core to avoid incurring a mortgage to buy one from CNH. Messicks shows the 8x8 converter to be Part No. 81878509R. Josephs Industries says they have one in stock. They are my go to and can be found at:

Josephs' core charge may be reasonable. If you tear her down, let us know what you find and how things turn out.
When you do a pressure test on the lockup circuit, the pressure should initially dip and then come back up to system pressure as you engage the lockup clutch. If the pressure drops and stays down, you likely have a major internal leak inside your torque converter. If the pressure drops to zero then I'd say you likely have the wrong converter. I definitely think it's possible to install the wrong one.
Thanks Bern for the info. One problem is, the pressure test from the port on the left side of the transmission does not check any solenoid valve circuits only the relief valve and any leakage. I would have to take the steering column off to access the for/rev valve and put a gauge on each one where the plugs are. The lockup valve has no place for a gauge. I know the pressure check from the side of the transmission will drop momentarily when cycling the for/rev valves but I'm not sure if it will drop when the lockup valve is cycled. I am going out and start it up and let it warm up and do some checking. The transmission works fine in both directions and still works in forward with the lockup solenoid engaged. I would expect it to quit pulling if the lockup system was just dumping pressure to the torque converter but it doesn't loose tractive effort. If I discover anything unusual or worth another post I will certainty do so. Thanks again...

Does this tractor work good in the torque converter mode, with the lockup button OFF? I have had a 445C with this transmission for 8 years, and I rarely use the Lockup function. I usually trailer haul this tractor to a new site rather than road it, where the lockup function would be useful.

Depending on your application, it may not be worth the time and expense to reactivate the lockup function.
The transmission works fine in all the gears except the lockup. I will take your advise and quit messing with it and just leave it non-working. I have another 445D 4WD that the lock does work and I'm with you on it's usefulness. Every time I push down on the inching pedal it kicks out or when cycling the the shuttle. Guess it is a road gear at best and it goes so fast it's hard to steer, cylinder swivels are loose so I don't use the lockup anyway on that one. 8 speeds is a plenty. Thanks

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