What is happening is the transmission is going through all four gears, then the torque converter locks up feeling like a "fifth" gear. This "fifth gear" will unlock as soon as it detects any significant load, and in fact has to unlock to allow the transmission to change down to third gear. It sounds like what you are feeling is the torque converter "hunting", dropping in and out of lock. Given that you are towing a load then this behaviour would not be considered unusual
I agree with that interpretation. I gives me the idea that a switch to cut the TCC at will might be interesting..and in fact I'd be tempted to use the ECO/PWR button for that function, since indeed it does not serve any real utility as it is. Fact is this TCC is not very sensitive to throttle inputs, and in most cases, it will let go only at same time as shifting to 3rd, contrary to my other car where each can almost be trigged independently at will (my Transport applies TCC to 3rd and 4th gear).
Cutting TCC would indeed save the clutch from "marginally" excessive torque in some circumstances ..and let the engine rev just a little faster so that it falls in the "torque" region.
THis would light up the CEL though....and at same time, the torque converter slip would induce some extra heat and then the suggested transmission cooler would be a welcome addition for long haul.
The split would be on blue/black stripe wire that goes from pin 22 on Transmission control module to TCC connector 2 at transmission solenoid plug.
www.geocities.com/lmp4203/kiasport/kiaauto2.gifI'll try that next summer: I think it will allow some hills to be taken in 4th without TCC instead of dropping to 3rd....will report.
