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-   -   My Speedo is off 3mph with 17" wheels (https://www.sportsmobileforum.com/forums/f10/my-speedo-is-off-3mph-with-17-wheels-1119.html)

Christopher Thwaites 05-09-2008 06:01 PM

My Speedo is off 3mph with 17" wheels
 
After my Quadvan conversiom my speedo reads about 3mph slower and 10% less miles traveled when compared to my GPS.
Quadvan says it's a simple adjustment done by a Ford dealer and takes just 15 minutes.
The Ford dealer says they adjust it and then dyno check it and they can never get better than a 5mph error! And they charge $150.
Which direction is the "smoke" coming from?

charlie56 05-09-2008 06:39 PM

SMB did mine as part of the conversion. My GPS matches the Speedometer exactly.

Christopher Thwaites 05-09-2008 06:47 PM

Quadvan normally does it but it was overlooked in the process. I think the dealer service guy at Hansel Ford was anxious to get home on a Friday afternoon.

jage 05-09-2008 07:07 PM

The work done by the dealership should be guarenteed for 1 year and 12,000 miles (or something like that). Go back, or to a different dealership and say: "Its still off".

My SMB is off, and it's costing me mileage on my warranty (~500 miles to date). It's your tire size and gearing that affects the speedo, and a computer setting that "corrects" it. If you find out how to DIY let us know (shouldn't scan guage or a similar product do this?)

yvrr 05-09-2008 08:27 PM

We investigated this when our van was new and finally learned that 2001 diesels could be changed out with a gear switch but it was impossible to fix 2001 gas vans....the Service Manager at the Ford dealer who sells vans to SMB West contacted Ford engineers, hoping to be able to reset the computer but it couldn't be done, at least at that time. I don't know if the gear swap is what SMB is doing now or not. And, yes, the odometer is also off. Our warranty will time out before it becomes null because of mileage so I don't worry about that.

I remember the first time we were driving off-road in 4WD right after we got our van and shifted into Low range. We were following a trail description in one of the guide books in Canyonlands NP and soon the waypoints seemed way off. I finally looked down at the speedometer and realized that the speedometer showed that I was driving at around 15-20 mph while I was actually just crawling along. Obviously, the odometer and speedometer were on the engine side of the transmission and not the output. There are probably electronically controlled by the RPM and gear setting....I'm old enough to only know about cable-controlled speedometers. <g>

BC 05-10-2008 01:07 AM

mine is off 3-4mph too, and have come to just live with it and know it and adjust accordingly. I had a tech adjust once at the dealer (no cost), but for some reason he couldnt get the software to give him the right options for tire size and it wasnt giving him the range he needed. I think John gave me the precise measurements needed at one point but never had them when I tried it, SMB should have them.

John Kalmbach 05-10-2008 01:46 AM

Speedo
 
All of the newer Ford vans have electronic sensors for the computerized speedometer. I don't know of a Scan Guage or similar device that will work to reprogram the computer. SMB purchased a unit through Ford that allowed the proper reprogramming to be done. It is very easy for SMB to do, as it only takes a few minutes. Most Ford dealers want to charge a minimum of one plus hour labor to reprogram, and some of them don't know how to do it properly. Mike at SMB West should be able to give you any of the information you need to pass on to your Ford dealer to ensure proper reprogramming.

Good Luck!
John K.


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