Yes. As Mal_Tx has previously posted, it is simply IMPOSSIBLE that your RPM's changed. You sure you werent a bit stoned? LOL . Every gear has its set RPM's at any given speed. No matter if its 5 Degrees or 120 degrees outside, 80MPH will always be at 3K. In any case, I think as the Government pushes more and more for better MPG's in future cars, we may be seeing 7MT's sooner or later.

 

What I'm trying to say it's impossible to run 3000K at 80 and 2800 at 70 in the same gear; do the math. 3000K at 80 means 26.67 mph for every 1K rpms in top gear, which equates to 2,625 @ 70. If your numbers were correct your tranny would be spinning at 1,400 rpm at 0 mph; impossible, but it could certainly be a bad speedo/speed sensor. Hope it makes sense now. Later.
JC

 

il check tomorrow...