Speedometer Inaccuracies

[scott2093]

google maps will show you accurate readings) and learnt which speed is where-30 is 35, 40 at 46-47, 50 at 60 and 70 at 83-it goes gradually up

Bonus speed trap alerts too...

 

[TheNewGuy]

I still haven't fixed the issue (I know it's been way too long). I haven't wanted to take it to a mechanic for fear of how much it would cost and I'd like to try to figure it out myself, but just haven't had much time for it.

Today though, I ran a test using an OBD-II scan tool because I noticed they could read the speed of the vehicle and the rpms. I found that neither the rpms or the speed matched what was shown on the cluster. I can't know if the rpm reading was correct, but I do know the speed reading was because it matched what google maps has been telling me.
I'm just confused because the scanner is getting the information from the vehicle, but every gauge on the cluster related to the speed is off.

So, I guess my question is why is the truck displaying the incorrect information when it has the correct information stored?