Hey everyone, I just purchased a 93 f150 and i'm new to the forum. The truck I purchased was originally a 2wd and was converted to a 4wd. When the previous owner did the swap, he installed a 9" rear and therefore did not have the rear mounted VSS and ABS sensor anymore...it is now located on the transfer case. From searching on the forum it seems that he probably used a pre 93 drivetrain, or at least transfer case since it is running off of the transfer output shaft. The speedo is reading however it is WAY off(at approx 60mph the speedo reads about 10-12 MPH!). My buddy is an ASE master tech at a transmission shop and both he and I are scratching our heads as to why it is reading but reading so low. I know there are a lot of variables since it was a custom swap job but I was just wondering if anyone on here has ever seen or heard of anything like this before and may have some input. The truck has an AOD in it so it is completely non electronic. Thanks and have a Merry Christmas!

 

The VSS on the transfer is not for a Ford, it probably puts out a lower voltage per cycle. The speedometer and ABS uses a voltage from the VSS to calculate the speed. The transfer case mounted one has fewer teeth therefore will produce less voltage per revolution.

 

Do you know of any way I can modify it to at least give me a close reading? I don't know if this is a common swap and all I can figure is to swap an 8.8 back in.

 

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It's something you're going to have to research to see if you can do it. I don't know the technical names for everything but basically you will need some kind of pulse signal multiplier, which will take the signal and add more pulses to it. When I was searching for odd electrical stuff I found that Painless Wiring had what I needed, but most isn't listed in catalogs so I had to call them directly to see if they had something that would work. They don't sell to the public either so they gave me the part number and I ordered through Summit.

Easiest would be to swap in the right rear, but there must be something out there to fix that. Plenty of people must swap in the 9", and I bet they still like to have a speedometer.