I am doing an overhaul on my '98 XK8 and tried to solve a transmission issue.

I kept getting the P0743 code (torque converter clutch system electrical), with no real signs from the transmission.

The code appears after 15-20 minutes of driving.



I dropped the pan and valve body, installed the upgraded pressure regulator valve from Transgo, changed the filter and fluid and the problem came straight back after driving moderately for 15 minutes. I think it might be the factory oil and filter, but no metal shavings in the oil were found, the oil itself looked reasonable for ~65k miles, the valvebody and pressure regulator valve housing have no visible damage.

I filled it with Zf lifeguard 5, the level is correct.



I searched the web for an answer, but different opinions are present.

Has anyone had a similar issue with the P0743 code?

Does anyone know what commonly is the cause of this code reoccurring?



Might the soulution be to change the solenoid for the torque converter clutch or is not worth a try?



If it's a gamble I'd rather drop the transmission and rebuild it, because I must say, the oil filling procedure is not my favourite way of spending an afternoon so I'd like to avoid doing it twice.