My speedo is inaccurite by 4mph to fast.At 65 on the speedo actual ground speed is 61.This has been checked by my GPS unit and a surprised police officer whom I asked to clock me.My question is does this also add more miles to my odometer.If it does it will be adding approx 3000 miles a year thus ending my warrantee to soon.I have been given different answers from different ford service managers.One says that there are different sensors for speed and distance .Manager#2 says he thinks they are the same but is not sure.Does anybody Know? Thanks!

Ps. my truck 2005 f150 xlt supercab flareside 4x4 with 5.4 and 3.73 rearend

 

This does absolutely end your warranty faster. You will have travelled an actual 33700 miles when the clock says 36000 miles. I think that all the manufacturers do this to shorten the warranty period, along with the defense for speeding tickets, ie you cant blame them for your ticket because the speedo said 60 and you were going 65. I put larger tires on my truck and did not adjust the PCM for it, thus I am going 65 mph when the speedo reads 61 mph. I will have gone almost 38,000 miles when the clock reads 36000 miles.

 

Thanks for the reply.The service department changed my instrument cluster thinking it would solve the speedo issue,it didn't! I've been thinking about putting on larger tires knowing that it will compensate(although that is not the only reason for tires) but my truck has the vibration problem and an appointment with the ford engineer in a couple of weeks.So I'm not making any changes to the truck until the vibe problem is completely solved.

 

Don't be too sure that you have the problem. Check your OD against the mile markers. The needle on the dash is not always right on the money. They get their info from same VSS, but needle error can add-subtract up to 4 mph. My Od is acurate, but with two clusters and a scangauge vs. GPS, I have found dial doesn't always match od.
Chris

 

I always thought the only speedometers that were truely accruate (calibrated) were the ones on cop cars?

 

I don't know about that .My corvette is dead ***** accurite as well as my wife's 2001 ford explorer sport trac.Again this was checked using my GPS and in the case of the Vette ,police radar(that was a great big oops).