I have a 1996 F150XL, and i recently obtained some 33x12.5" super swampers.
the problem i have now is my speedo is off. like, way off.
ive already gotten one ticket for it, and i need to get this fixed before it happens again, how do i need to go about recalibrating the speedometer since it is electric?

 

Programing for tire size,

Locate the connector at the bottom of the instrument panel below the center of the glove box. Should be LB/Y, has "PSOM" printed on the connector in white lettering. Held in place with a plastic retainer.

Insert a jumper wire or alligator clip in service wire and clip other end to vehicle ground with the key in the OFF position.

Turn key to RUN while holding down the trip odometer RESET button on the speedometer.
Release RESET button The Speedometer will prove out(sweep across dial and back). The English/Metric and revision levels will be displayed. The last number of the display id the dealer mode lockout count. This count shows the number of allowable conversion constant changes remaining. When the count is zero (0), no additional changes can be made to this instrument cluster. If a revisions required a service instrument cluster must be ordered.
Press and release RESET button again and PSOM conversion constant without the decimal point will be displayed followed by the word CAL.

Press and release the odometer SELECT button as many times as necessary to change the conversion constant to the correct value. The constant will only increase (not decrease) when the SELECT button is pressed so reducing the constant means counting up until the constant jumps to the bottom of the scale and begins counting up from there.

Pressing and releasing the RESET button to lock in the new conversion constant reduces the number of times the PSOM can be reprogrammed by one count. If you change your mind and want to go back to the old conversion constant, turn the key OFF BEFORE you lock in the new constant.

You should be able to get your tires conversion constant from the manufactures web site.

Here is more if you want to do the "math" for yourself, https://www.ford-trucks.com/forums/7...tire-size.html

 

your 33's threw your speedo off that bad? damn...my 35's throw it off like 4 miles an hour at 50 but like 10 if I'm doing like 75 lol but that's pretty intense

 

I re-calibrated the speedo in my '96 F350 today using the article by Benjamin Ratterree, I have 315/75-16 tires on it and reset the conversion constant to 900 from the stock 980. Borrowed a GPS that shows speed, it showed I was dead on from 10 to 50 and showing just a little high by 65. Now I just want to get a new instrument cluster that has a tach.

 

Shout out to the moderator: this thread, along with this article link: HOW TO RECALIBRATE THE SPEEDOMETER ON 92-96 FORD F-SERIES AND BRONCO .: Articles really need to go into the FAQ sticky at the top of this thread.

Also, I notice that both the article and the instructions above only talk about recalibrating for change in tire size. Is there any additional info available for when you change diff gear ratios?

 

Gear ratios don't affect the speedo since it gets a signal from the sensor on the rear diff, and the sensor ring mounted on the diff carrier inside remains the same regardless what gears are in the axle.

 

And there's a separate sensor in the tranny for RPM? Cool!

 

no,RPM is revolutions per minute of the engine,has nothing to do with the tranny.

 

Well, yeah. But where is the RPM sensor physically located then? I used search and found lots of hits that tell me where it is for the Diesel, but none for the 302.

 

There is no "RPM sensor" per say, the EEC gets a pulse train signal from the TFI(ignition) module which is fed from a pickup inside the distributor.