I have an 89 351 W Bronco. I currently have r15 33 X 12.5 tires on the vehicle and I need to know how to reprogram the speedometer....

ANyclues? Thanks in advance.



Mike

 

If that is an electric version this is the procedure from Broncodata.com

Resetting Recalibrating your PSOM for the Correct Speed


Ford uses a module called the PSOM to hold your speed calibration information as well as your odometer memory. Pressing the select whith the truck on will change the display from your actual mile portion to the trip meter and back. When displaying the trip meter you can reset it by holding down the reset (duh!). If you hold the Reset button while turning the key forward to Run, and then releasing the Reset, you will see your speed ratio constant or conversion constant. The needle will do a full sweep test, and the odometer display will show "E ## #", meaning English units, the microprocessor revision and the conversion constant lockout count. Pressing Reset again shows "###CAL", which is the conversion constant (without a decimal).


If you want to change the constant, find the single-wire connector under the glove box and ground the LB-Y wire before turning the key on (you still have to hold the Reset, as before). Everything is the same as before, except "CAL" will flash, indicating that the constant can now be changed. Press the Select button to decrease the constant by 0.01, each time. When the constant reaches 5.00, it goes back to 11.00 . Larger tires or fewer teeth on the tone ring require a lower constant - R&P changes have no effect. When you have the constant you want, press the Reset button to lock it in. THIS WILL DECREASE THE LOCKOUT COUNT BY 1 - WHEN IT REACHES 0, NO FURTHER CHANGES CAN BE MADE. To abort the changes and maintain the lockout count, turn the key off before pressing Reset. When finished, turn the key off and disconnect the LB-Y wire from ground.

The formula for finding the constant for your tire size is as follows:


Formulas are coming!


This yields the Following Chart: Note tire size does not take in consideration actual tire size not does it take under consideration tires squatting under the load of the truck. Ford allowed 1.33 inchs for the stock 31 inch tire for such. Thus the stock constant is 9.18 and is for a tire size of 29.67 inches.

Tire Size
Tire Height Revolutions Per Mile Aspect Ratio
29 29 696 9.39
30 30 673 9.08
31 31 651 8.79
32 32 631 8.51
33 33 611 8.25
34 34 593 8.01
35 35 577 7.78
36 36 561 7.57
37 37 545 7.36
38 38 531 7.17
39 39 517 6.98
40 40 504 6.81
41 41 492 6.64
42 42 480 6.49
43 43 469 6.34
44 44 458 6.19
45 45 448 6.05
P275/75R15 31.25 663 8.95
P265/75R15 30.66 658 8.89
P275/60R17 30.00 721 9.73
P235/75R15 28.89 699 9.43
P215/75R15 27.71 729 9.84



Resetting procedure provided by Steve. Formulas received direct from the manufacturer of the PSOM

 

We did this on fast_eddy's 96 and it worked, but we couldn't figure it out on my 92. are they different?

 

89 had mechanical speedometers, so you'll have to get a different gear for the cable that goes into the transfer case.

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[font color="green"]1995 F-150 Supercab XLT longbed 4x4 302 M5OD [/font]31x10.50's
[font color="green"]1986 F-150 4x4 300 I6 NP435 [/font]Warn hubs, DeeZee bed caps, '96 XLT bench seat, new paint job

 

Thanks for the help guys, but one more question, where can I get one of these gears, and how do I know what to do with it when I get it. Again, many thanks.


Mike:-X11

 

8.89 for 265/75/15????

i thought it was supposed to be 9.18

 

I had the 265/75/15's stock on my 94 and it was 918 from the factory. I used the odometer to recalibrate mine when I changed my tires and my speedo is right on the money. There is something wrong with those #'s

 

These are the calibration codes that I have used a number of F-150's and Broncos, everything from a couple of 92 Broncos, a 93, a few 94's to a 95 F-150.

37 inch tires = 773
35 inch tires = 815
33 inch tires = 864
32 inch tires = 896
31 inch tires = 918
235/75R15 = 972

These equasions seem to be right on the money.