92 Explorer Speedometer cable and calibration

[CaptainKermit]

Hi Everybody. First time on this forum and a Ford Explorer rookie.

I just bought a 1992 Ford Explorer for my daughter to drive to work, especially in the snow this winter, and I have very little experience with Fords. Here is my dilemma and questions. I drove the car today and the speedometer said 40 mph when I was actually going 50 mph. When I accelerated to 50 mph on the speedometer I was actually going 60 mph. I just checked the standard tires for this vehicle and they should be P225 / 70 R15SL but have P235 / 75 R15.

I have done some reading comments about replacing the driven gears, replacing the instrument panel, etc. yet I have never done this type of work on a car. I also am not sure if I have found the speedometer cable location on the tail end of the transmission.

1) Is this the speedometer cable connection to the transmission?

2) Suggestions for my speed calibration issue?

 

[Rick]

Yes that is the speedometer cable.

It's possible that the differential gears were changed which would affect the speedo reading. Another possibility is that the transmission was swapped at some point and the gear in the tranny doesn't match the factor differential gearing.

I have a vehicle with an inaccurate speedometer. I use the Ulysses app on my smartphone to act as my full time speedometer. I attach the phone to the dash with heavy duty velcro so it's always in front of me.

 

[RangerX]

You can disconnect the cable right where you've circled it, and swap the plastic gear inside to a different spline count, to correct the problem. Somewhere on this site, there's a chart showing the different gears and their corresponding color.

 

[Rick]

Here is a link for you to check out:
Speedometer Gear Color Code Specification Chart With Formulas, And Ford Part Numbers.

 

[larrydd999]

Just FYI, the P235/75 R15 is a 'standard' alternative size, and both of my GEN1 Explorers came with that size. IMO that different tire should not result in that great a difference in the speedometer reading. If you've a mind to investigate farther, I'd check the legend plate on the driver's door for the original rear end ratio against the actual ratio from rotating the axle. In any case, as noted above you can check and replace the gear.

 

[CaptainKermit]

Excellent! thanks each of you for your comments. I did the conversion from the link and after finding none available from a local Ford Dealership I went to an auto pick and pull and found the one I needed. My Explorer now is showing the correct speed.