I have a 94 F-150 302 2WD E4oD tranny stock everything. Just changed rearend gears 3.08 to 3.55 do I need to recal speedo I can't find a gear to change. I have heard you do not need to recal it. Is this true or is there a sensor to change? please help

Jleach

 

No gear change is needed. Instead, reprogram the instrument cluster using the following procedure:

Locate the dealer mode programming enable single-terminal connector. The
connector is located at the bottom of the instrument panel below the center
of the glove box. On all vehicles, the dealer mode enable wire is Circuit 567(LB/Y).
Insert a jumper wire or alligator clip in service wire and clip other end
to vehicle ground with the key in the OFF postition.
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
revision is 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.
The new conversion constant necessary to correct the speedometer can be
found by determining the current percentage error. One way to do this is by
comparing the indicated miles versus mile markers on an interstate trip.
The longer the trip, the better indication of the error since interstate
mile markers are not always exactly 1 mile but the average is very close to 1 mile.
Going to taller tires (indicated miles less than true miles) will mean the conversion
constant must be reduced by the same percentage as the speedometer error and
going to smaller tires (or a numerically higher rear end ratio) means the conversion
constant must be increased.

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.
Note: 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.
When the new correct value is displayed in the odometer window, press and
release the RESET button to lock in the new conversion constant.
Turn the key OFF and disconnect the ground wire and check to see that the
speedo works correctly.

 

If you have not changed tire sizes there should not be a need to change the calibration. On my '93 the speedometer runs off of the Ring Gear. I haved changed both tires and gears(3.08-4.10) with no calibration to the speedometer and found that the difference in mileage/indicated speed remained constant. If you have someone with a stock vehicle who is willing to take a long drive alongside you it might help put you in the ballpark of determining the percentage needed to change the formula(if necessary).

WH.

 

Will this calibration work on newer model 99-2001 F150's ?