Anyone out there have a handheld GPS? I just got one, and was playing with it in my truck the other day. I had my cruise set at 60 mph for about 10mi and the GPS was reading 53mph. I have not changed tires or gears, does ford calibrate theese speedo's that far off? Or is it on 2wd Lariat's that get larger tires than 2wd XL & XLT's, and ford does not recalibrate the speedo? If so, how many of my 36000mi am I loosing on my warrenty because of this?
Jeff

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1999 F-150 Lariat 4X2
Reg cab Short box Styleside
5.4L 3.55ls
Deep Wedgwood Blue/Silver
Lund Interceptor hood shield
VentVisors
Class III hitch
Ford molded mud guards
Soft tonneau cover
Factory CD with changer (thanks Dusty)
Tinted windows
Factory fog light kit

http://www.fortunecity.com/silversto...ton54home.html

 

That's a pretty big error. Check the GPS in another vehicle (just to be 100% sure), then have the dealer fix your speedometer. You'll lose about 12% [4200] of your warranty miles at the current error rate.

 

Thanks nomo, actually I borrowed my brother-in-law's GPS today and used both to test. Both GPS were within 1mph of each other. The higher the speed the farther off the speedo gets. 7mph off at an indicated 65 on the speedo.
Anyone know if the speedo is controlled through the computer? I just had my computer replaced last week (supposed to fix rough idle, but did not), could this cause the error?
Jeff

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1999 F-150 Lariat 4X2
Reg cab Short box Styleside
5.4L 3.55ls
Deep Wedgwood Blue/Silver
Lund Interceptor hood shield
VentVisors
Class III hitch
Ford molded mud guards
Soft tonneau cover
Factory CD with changer (thanks Dusty)
Tinted windows
Factory fog light kit

http://www.fortunecity.com/silversto...ton54home.html

 

The speedo IS controlled through the computer on the '99 and '00 models

 

Well I see what Ford is doing they make the speedo read faster so the warrenty runs out faster . So if your computer is screwed up then that may be your problem I think the speedo should be set right from the factory when they build it no matter what size tires they put on it.

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2000 F150 XLT Reg. cab
4.6 Triton Engine
4x2 3.55 rear end gear
sliding rear window
automatic keyless entry
white styleside short box

 

Sounds like the dealer didn't program the new computer for your tire size. They should correct it for free.

 

Relying upon a GPS system to test the land speed of your vehicle is like using a rope with knots to test the speed of your boat. The intentional DOD degradation of the GPS signal makes it totally useless for this function. Stopwatch timing between mile markers is much more accurate. Set up your GPS on a bench outside sometime and watch both the position and the altitude vary while the GPS remains stationary. Even with a differential beacon receiver it won't be accurate enough for speed determination.

adp
Black L '99

 

That was part of what I was looking for, is the GPS accurate for speed? I have talked to the dealer and they tell me the speedo is not controlled by the computer. I thought I had read on here it was. It is going in Friday to check the speedo and again with the rough idle.
Jeff

------------------
1999 F-150 Lariat 4X2
Reg cab Short box Styleside
5.4L 3.55ls
Deep Wedgwood Blue/Silver
Lund Interceptor hood shield
VentVisors
Class III hitch
Ford molded mud guards
Soft tonneau cover
Factory CD with changer (thanks Dusty)
Tinted windows
Factory fog light kit

http://www.fortunecity.com/silversto...ton54home.html