I have a question about what unlocks the torque converter when in Over Drive and cruising at 50-55mph? My old 97 would lock up in OD and stay locked unless you hit the brakes or the speed dropped below 50. If you were locked up and you put the pedal to the floor it would just keep pulling and would never kick down. Now on my new 07 the torque converter will stay locked even if you apply the brake and will unlock when you drop below around 50mph. The think that struck me as different was that when in OD and cruising at 50-55mph, if you get into the pedal it kicks down like a gasser would. My question is, is this correct?? Maybe someone could explain it to me. Thanks in advance Pete

 

It seems to bust out of lockup about 2/3 throttle. It may be because accountants have more design input than do engineers and don't feel the need to include a torque converter that when locked up will handle the engine's full torque for the long term. There are threads that describe how to make the lockup user controlled using a "mystery switch" that grounds a particular pin at the tranny as I recall.

 

Thats what I figured. Just never considered doing the mystery switch because I didn't want to fry the tranny!!!!!

 

what is your pedal position when it kicks down at that speed and how many miles on it ?

 

It has 4600 miles on it. The pedal position was around 2/3 and speed was about 60mph.

 

Same with my truck. Have to go easy on the peddle until you are above 55 mph, then you can go to about 2/3 throttle. I run mine in Tow/Haul mode all the time, which locks up in 3rd gear at 30-35 mph and 4th gear locks at 50 mph. The same thing happens in 3rd when below 40 mph.

 

if your RPM is low with lots of fuel and not much boost your EGTs will be very high, thats the only reason I can think they may have programmed it that way. above about 70mph it will not unlock or downshift.

 

Thanks for all the info. Pete