Inaccurate speedo-I read all associated posts

[mudpaws]

Hey, I have a 2001 Ranger 4x4 Super Cab with the 5R55E 5-speed auto trans. I have the stock size tires on it (P245-75/16). My speedo reads +5 MPH all the time that I can tell. I've gone through those Police "speed boxes" and seen it them say 41 MPH, for example, and the truck is up to 45 MPH. What is going on here? Also- based on how long this has been happening (I've owned the truck from 6/22/2012, with 103,600 miles to present-it now has 115k and change) could the odometer be off, and by how much?

Thanks! I know some of you can help with this dilemma.

 

[SenorNoob]

I see a few possibilities:

The speedtrap is wrong. I wouldn't be surprised if it's calibrated a little high to scare people.

Those aren't the stock size tires for the ECU/GEM on your truck.

You're just noticing the stock "variance". I hate it myself.

The speedometer needle has been off and was placed back incorrectly.

 

[mudpaws]

Hmm...like I said, I'm not sure what happened before owning this rig. I do know it was in some sort of collision, and repainted on the right side.
That speed reader is near a college here, just mounted up on a utility pole. Gotta check it with my wife's new van.
I've been driving for a long time, and can tell I'm not going the speed the truck says.
Interesting about the needle thing. I do know that the stock size tires are not new. They do have good depth left, and they are the proper size.

I'll see if I can get to taking the needle off and clocking it back.
Can the ECU/GEM be calibrated, and if so, how?

Hmm Hmm Hmmmm lol. Maybe I'll just wait til I do my lift and go to 32s. That should make it correct, hopefully!
Thanks for your help so far..

 

[SenorNoob]

ADSM08 has the procedure for the needle posted here somewhere.

The ECU/GEM can be adjusted to any stock tire size afaik.

Sorry I can't be more help than that. IDK much about the newer models.