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Torque converter acting strange?
2009 cclb 90k miles with tuned hs mini maxx since 35k. been noticing as of late that on the highway when I pass someone and reach about 75-80mph the torque converter unlocks entirely, and remains unlocked even when I let off the pedal for a second or two. Then it locks back up and will unlock again if I try to pick up the speed. This happens with moderate throttle, I rarely ever beat on the truck. I haven't tried recreating the situation under full throttle for fear of causing damage. I get no codes at all. I have wondered if fluid temp makes a difference in this situation but it doesn't seem to matter warm or cold it still happens.
I have read something about the transmission pump losing pressure over time causing this. But I'm not sure. Fluid is clean, but has about 40k miles on the fluid. The transmission feels great in everyday driving and spirited fun. I am positive below 75mph there is no slipping that feels outside of normal operation. I checked fluid level because since the last tranny service it is wet with fluid around the pan. Fluid level looks fine even though the dipsticks are horrific on these new trucks. Does anyone have insight or experience with this? Should I have the tranny flushed and see if that helps?
Have a good one,
2009 F-350 XLT CC LB 6.4 powerstroke, H&S mini maxx, Flo-pro 5" dp back exhaust, AFE intake...
1977 F-150, built 300 six, M5OD 5 speed