Hey everybody,

I've got a 94 F-150 w/ the 5.0 litre and the 4r70w. I recently put 33's on the truck and threw the speedo off. With the electronic speedometer, how do I get that back into calibration? I'm also going to go with 4.10's in the rear, and wondered if that would affect the speedometer, and should I wait to get it calibrated after the gear swap.

Thanks, Pete

 

Pete
Changing your gears will not affect you speedometer.Changing your tires (height) will throw off the speedo.I used the following to recalibrate my Bronco with excellent results.
Just one word of caution the module can only be programmed 6 times

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 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
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.


Joe
94 Bronco XLT,5.8,E4OD

 

[font size="1" color="#FF0000"]LAST EDITED ON 12-Feb-01 AT 08:23 PM (EST)[/font][p]Joe, would using the following formula also work to determine the percentage error? I got it from http://www.tciauto.com/tech_info/speedo_gears.htm

Tire Revolutions per mile = 20168/tire diameter

With this formula, I came out to 576.23 rev. p/mile for the new 35 inch tires, and 695.45 rev. p/mile for the stock 29 inch tires.

To figure the percentage error, I divided the two (576.23/695.45) to get .8285. My question is, would I need to adjust my conversion constant 83 points, or 17 points??

Thanks for the help )

TrailDawg
1993 F150 2WD
4.9L-Auto
Pro-Comp Stage-2 6" lift
Auburn Pro-Series Diff. w/4.56:1 gears
35x12.50x15 General Grabber MT's