Just installed 265/75/16 on my 97 F150. After reading all your posts, I spoke with the dealer, who thought that to adjust the speedo, they would have to reprogram the computer, however, the adjustment is made in increments of 6 mph., so therefore, since I'm only off by 3 mph, it would not do any good. He did not know of a gear that I could replace to correct the speedo. He also said that to correct the loss of low end torque, I went from a 3.55 to a 3.36, they could reprogramt he computer to comepensate and bring the torque back to a 3.55. Does this sound right. The speedo I can believe, but I'm not sure about bringing the gear ratio back up to 3.55 by reprogramming. Maybe, Anybody know. Also he said it would cost between $79 & $219, depending on how long it took. All replies are appreciated. Thanks

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97 F-150 Lariat, Leather, Ext. Cab
White/Champagne, 4.6L, Auto.
Tinted Windows/Bedmat
Toolbox/Lund Bug Deflector
Dual Exhaust
Grille Guard
Chrome bed rails
265/70/16 Goodyear Wrangler Rt/S

 

They can reprogram your computer to compensate for the change in the differential ratio? I would like to know more about this too, I would be very interested in getting it reprogramed to bring it back to 3.55. Im pretty sure my ratio dropped the same amout as yours did, WindDancer, ill have to look it up. For me too, any replies are appreciated.

Brian

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98 F150 XLT Supercab 4X4
4.6L V8 3.55LS
Tonno Cover, Brush Guard, Dukes of Hazzard Dixie Horn, 2 150 watt KC Daylighters, Cobra CB Radio, BF Goodrich All Terrains 265/75/16
http://hometown.aol.com/barto24/brianstruck.html
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2000 Excursion Limited 4X4, Black, V-10, 3.73 LS, Tow Mirrors

 

According to one of the mechanics at my local dealer, 1997 trucks are slightly more difficult to re-configure for different tire sizes. 97's require entering a rather lengthy formula in the computer based on tire size & gear ratio. He said 98s and later are easier to do. He checked mine when I bought it (previous owner had changed tires) and even ran it side-by-side with a stock truck and the speedo was right on. The only time I notice any power loss is at highway speeds on hills; usually turn the overdrive off when this occurs.

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97 150 SC 4x4, 4.6, 3.55, 265/75R16, 1st Ford truck; bought 4-00 with 55500 miles

Added: Ford running boards, Ford molded mud guards (f&r), Class IV receiver, Delta Truk Pockit toolbox, Dupli-Color roll-on liner on bed front & sides, Bed mat, Ventshade Stepshields

 

On a 97 F150 you don't reprogram the computer to reset the speedo. There should be a speedo gear on the side of the transmission. I think they changed to computer controlled speedos in 99, but in 97 you have to buy a gear. Very, very cheap and easy to do this.

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1997 F-150 Lariat
Ext Cab Short Box
4x4 Off Road Package
3.55 Gears
285/75 R16 Kelly Springfield Trailcutter RTs



My 2 cents worth

If you're gonna stroke it, POWERSTROKE IT!!!

http://www.powerstroke73.homestead.com/

 

You cannot change the rear end ratio with the computer. Those are real gears, not software. To get the torque back, you would need to go to a 3.73 or even a 4.10 depending on how big the tires are.

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'99 F-150 S/C 5.4, 3.55 Wedgewood/silver

 

Well i DID have my hopes up, but oh well, i still love my truck no matter what rear end ratio.

 

Powerstroke is correct. 97-98 are done with a gear. 99-01 are electronic. Do a search. There is a calculator in one of the posts that will tell you the exact amount of teeth you'll need. Sounds like the dealer here is full of it.