i thought it was taken off the a/c blower speed.

I would trust my car's speed reading before i trust a GPS, thats for sure

In my vehicle, my GPS (I use my Passport as a "primary" spedo) indicates the exact same thing...per GPS I'm going 70 while my Z's spedo shows 71 or so.

Then again, those highway readout radar sets I occasionally will usually show something different than what my GPS or the car's spedo is showing!

but then if your tires are over/under inflated...

oh wait, doesnt matter cause it's not connected to the tires...

I am quite sure that it IS connected to the wheels since I had it happen in two cars.

speed flew up on the ice while i was pretty much standing still

Any car with ABS has wheel spin sensors. It is very easy to use this source of the speedo. In fact, I believe it is Subaru that uses the wheel spin sensors as their "flat tire detection system". It monitors all the wheels and if one is spinning more than the others, then the tire is low on air...hence smaller.

If I were Nissan, I would use the front wheels for the speedo. The car is already monitoring the tire rotation, so why not feed the rotation into a calculator.

As a follow-up...In the service manuals. The Vehicle Speed Signal is in the Wheels and Tire section. So I would bet against the tranny.

Bump from the dead

Any difinitive answer?