Edge 2010 TCC slipage problem

[sea201012]

Hi everyone. I got a used EDGE 2010 with 120000km mileage months ago. When the speed with 40~50km/h at gear4, can feel vibration very clearly. After searching a lot of information including the repair manual, I think there should be a TCC slip issue. Tried to get a 24oz Lucas oil and filled it into the transmission, before doing that I pulled out about 1L of fluid to ensure that the transmission fluid level will not be too high. The symptoms remain the same. So I decided to bypass the TCC solenoid to avoid this vibration. I find the TCC solenoid wire which is blue/gray from the manual and finally disconnected it. Now I got a yellow wrench sign-on dashboard, the PCM may detect that the TCC solenoid circuit is open. Generally, TCC failure will cause losing 6% fuel economy, and the transmission fluid temp will be higher. Can I wire a switch into the TCC solenoid circuit? I'm not sure the PCM will give the commander for engaging the TCC now, and maybe it can not work properly when the parameters are different from the default program setting.  By the way the first generation of GM 6F50 is the worst gearbox I've ever come across.