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In March the transmission had a no or delayed 1-2 and 2-3 shift condition. The transmission and cooling lines were flushed, the 3-4 accumulator spring, along with the governor solenoid and pressure/temperature transducer replaced. The fluid was changed to Valvoline synthetic +4. The transmission shifted great after the repair. The end of July I go on a 1000 mi "camping trip" pulling my 5th wheel with the boat behind it. I find out that I have no torque convertor lock up! This had happened once before in May of 2018 for about 10 miles. Now, cruising at 60 mph the RPMs are1900±; when accelerating from 60 mph the RPM increase rapidly to 2400-2700 depending on the load and peddle position; when the accelerator peddle is released at 60 mph the RPMs drop to 1400. The transmission temperature, measured in the cooling line between the pump and engine coolant heat exchanger, is normally 160-170° but with no lock up the temperature is 190° ±100°. When going up long grades the temperature climbs rapidly and when it reaches 240° I pull off the road, put the transmission in neutral with the engine at idle, and after 15 minutes the fluid cools to 190° then I can finish the grade. At 60 mph with the 'Mystery' switch on the RPMs still increase rapidly when accelerating indicating the torque convertor is not locked; when the accelerator peddle is released there is a drop of only 50 RPMs and there is engine breaking going down hills but the truck can come to a full stop in 3ed or 4th lock up, with the switch still engaged, and the engine will not stall. The fluid is still clean and full, the APPs in live data shows good with a smooth 0-100% transition and AC voltage is at .03v ±.005. Ohm testing the solenoids shows: 3-4 shift solenoid 32.8Ω, TCC solenoid 32.8Ω, and the new Borg Warner governor solenoid 6.2Ω. What I'm thinking is either a lose of pressure to the TCC, a poorly opening weak solenoid, or a bad TCC.