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Jun 17, 1999 | 12:29 PM

matt_1

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speedometer

I recently finished lifting my 94 f150. Along with the lift I added 33 inch tires. I know my speedometer is off now and I would like to recalibrate it. What do I need to do this or where could I see about taking it to have this done? Thanks for any help.

Matt

Jun 23, 1999 | 07:03 AM

Chuck P.

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From: SE PA

speedometer

Hey Matt,
Since no one else replied, I'll give it a shot! When I changed tire size (33") I found a place that specializes in speedo correction. They are local here, but I'm sure there has to be others who do this. They have done mine (79-150-4x4) a total of three times. They changed the gear at the tail housing of the t-case, were it's driven from. It cost me just over fifty bucks each time including the gear. But now it's certified to be correct. Oh, it didn't take them 3 tries to get it right- I changed tire size to 35's then changed gear ratio to 4.10's from 3.50's. I found them in the yellow pages under speedometers. If you have a stopwatch and a milemarked highway, you can at least get in the ballpark with the amount it's off- run a timed mile at 60 mph-it should take 60sec. you can roughly figure about one mph over for every sec. under, or vise-versa.
With 33's if I recall it only took me about 55 sec. to cover a mile at 60 mph (indicated), that = about a true speed of 65 or 66 mph. Good luck gettin' it corrected. Chuck P.

Jun 24, 1999 | 06:46 AM

Chuck P.

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From: SE PA

speedometer

Hey Matt, came across some info which may or may not help. It seems that in the later models the speedo is not mech. driven but is programmed into the "black box"-there is suppose to be 5 different calibrations to correct for different rear-end ratios and tire sizes. Bad news-problem is I don't know if just anyone can change this with a laptop or if ya need a new chip. Best place to start would be with the dealer and find out if this is true or not! Good luck, Chuck P.

Jun 28, 1999 | 08:21 PM

JoeyB

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speedometer

A couple of years ago I changed the gears on my 93 E 150 from 3.55 to 4.10. I did some research that might help. After calling 4 different Ford dealers I finally found out that the new trucks use the rear ABS sensor in the rear axle to send a signal to the speedo. Changing gear ratios does not effect the speedo but changing tire sizes will. You need to have the speedometer constant changed in your speedometer.It is a real pain to change and can only be done a couple of times. I could not find anyone in NJ (locally) that would do it.Lucky for me I didn't need to do it.Hope this helps.

Jul 20, 1999 | 06:28 AM

Tom1.0

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speedometer

Matt, here's a product that not only corrects for tire size for speedometer, but also compensates for computer problems and transmission shifting errors caused by different tire sizes.
Saw this on ShadeTreeMechanics.Hope this helps.
FEATURED PRODUCTS
The Recalibrator & The Interceptor from Auto Trans, Inc. - Edmonton, Alberta / Canada. Most Auto Trans, Inc. products are available through your local distributors. Please call (888) 453-3767 for more information.