What would cause my speedometer to be off? When my truck is showing I am going 65mph, i am only going 62mph according to traffic radar signs, my prorable GPS, and my cell phone GPS that are all current and real readings in my other cars... My speedo is a consistant 3mph off the real speed.... How that can be fixed?

 

mine is off by about the same amount. Not sure how one would fix the speedo.

 

My 2011 does the same thing, but I believe my '08 was pretty accurate.

I got an AE scan tool a couple weeks ago that has the ability to reprogram tire size. Should support my 2011 in November, I'll see if this fixes it for me.

Scott, if we ever meet again I can reprogram yours for your current tire size. The same offer goes for anyone else on here.

 

Its very strange that these would be off..... I understand if you get larger wheels/tires, but my wheels/tires are stock.... Plan to come to Florida?

 

Mine are still stock size, just a different tread. Has not been a concern of mine. I wonder though why it is.

 

would be interesting to know your true rollout size vs the calculated size..

mark your tire at the bottom, and the driveway, roll one turn til the mark is at the bottom again.. mark driveway.. measure between marks. then use the discount tire size calc tool to get the calculated size

Tire Dimensions Made Simple - Discount Tire

how close are they? 4.8% on my 245/75/17 is 4.5 inches circumference
94.11 (95.2%) vs 98.86 (calculated)

65/62 = 1.0483

smaller actual size will show a faster speed..

Sam

 

ETKMS

The whistle ring type you describe is the same I had when I picked up my used truck with 59,000 km on it. It took them a while to find it (both turbos changed first ) but later it turned out to be a ceased EGT valve that rings and won't move in the turbo pipe on the passenger side turbo. No cab off to fix it. If you would like a copy of my dealer work sheet I will send it to you. Mine was loud when it happened and intermitten. Hrad to pin point by the dealer. It made a big loud whistle/ring in the dealer's service bay finally and they said they would keep it until it was fixed, 10 days later they found it

Bruce
2008 F250 Lariat 4x4 fully Ford decked

 

Thanks for the help, but that issue of mine was already taken care of, both turbos were replaced and so was a bad downpipe gasket.