Hi guys, looking for some help with an older Komatsu 655-3C machine. Problem is grader is slipping in higher ranges. I’ve checked main and lock up pressures all good. I’ve isolated it down to my 3 main clutches are not showing any pressure when selected in appropriate gear. FL, R,FH……1st,2nd,3rd,4th are all showing pressure when commanded. I’ve check solenoid resistances and pressure switches. All good. I jump power from 1st clutch connector to FL clutch connector and it shows 300ish psi. This confirms solenoid, clutch pack should be ok mechanically. What I have found further is on my 1,2,3,4 clutches I’m getting 4.8 to 5 volts with key on and gear shifted to appropriate range. My 3 main clutches are only showing 1.7 volts max as soon as you plug into solenoid. All solenoid connectors are showing 24 volts unplugged from solenoids. I’ve pinned out from trans controller to connector at each main clutch connector and 0.5 ohms seems ok. I find it very strange all 3 are not working. I’ve checked voltage for FL clutch directly back probed from trans controller and same result showing 1.7 volts, so I don’t believe it’s a wiring issue in harness from cab to rear. I’m leaning towards a transmission controller issue as it works when I swap solenoid connectors with 1,2,3,4 solenoid power. Possible weak or dead driver in trans controller related to the 3 main clutch circuits. I’ve also checked switches on the gear lever to trans controller, all change to 24volts when you move shifter to gear. Kinda stumped here not sure what else to do, but it’s definitely electric and there are no codes. I don’t want to miss something and buy a million dollar trans controller if I don’t need to. Any advice would be appreciated. Thanks
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