Overdrive switch?

I was just wondering if it is possible to make overdrive switchable? I say cuz I kind of sucks you can't use 5th gear w/o overdrive. So instead of having to switch in to 4th gear to turn it off, have a switch somewhere so you can turn it on/off yourself.

 

5th gear is overdrive. So if you don't want to overdrive, shift into 4th which is a 1:1 ratio.

 

Yeah. What he said ^^^

 

Sounds like he's talking about the torque converter locking up.

 

Yes, I was wanting a switch the make it where I can stop the converter from locking up. I have been having problems where the truck has no go when I turn on my AC and I have noticed it is better when I have it in 4th gear, not allowing the converter to lock up. I have been watching the trans pan and converter temp on my scanner and the converter even while just sitting in drive will continue to get high, I mean in the 190+ range and it is norm around 160-165 area. That's why I have been suspecting it to be something with the converter or the electronics having to do with it. If I can control it manually, I can start to eliminate things and find out what the hell is going on. It only does it with the AC on and it started out of no where, instantly.