Nissan Repair: 2001 frontier trans. slippage, overdrive switch, torque converter

Question
I have a 2001 Frontier that seems to have a loss of power at 70 MPH around 3000 RPM. Now, I've had this truck for almost 3 years and I know this thing isn't supposed to go 3k RPMs at 70 MPH. I think it's the Over Drive gear slipping, possibly not catching the Torque Converter... I don't know, I don't have a lot of experience with newer auto trannies. Anyway, the Nissan Dealers (2) have hooked it up to the diagnostics and tell me there is nothing wrong. But, they haven't seen it go to 3k RPM's at 70 MPH during the 3 test drives done and $150 I've spent having them look at it.  

Answer
Shawn,

Make sure the overdrive button is left on and the system will go into overdrive after it gets to operating temperature.  Remember that the transmission has a lock up torque converter as well.  And, the way the thing works is first it gets to fourth and the lock up converter applies.  If you take the overdrive button and press does the transmission downshift or does it stay in overdrive?  Check out the operation and give me a email back and we'll discuss more.  You could have a defective overdrive switch if the dealers have not found the problem that you have experienced.