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Np231 speedometer question


Well-known member
Mar 7, 2022
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I currently have an NP231 DHD in my truck. I also have an NP231D that came with the speedo hole on the housing. I'm looking to swap the rear axle (not to the one I asked about a couple weeks ago), but the possible transplant axle does not have a speedo hole/plug where the current speedo plug is. My question is, can I get a SYE kit with the speedo hole in the tail housing and use that to determine speed or do I need a rear axle with the speedo hole on it? Is it as simple as splicing the wires to correct speedo?
This is what I currently have:

This is what I'm asking if I can do to make the speedometer work?


Thank you.
Most of the 89-95ish dodge products have a mechanical to electric transducer in the tcase. Should fit the hole in that sye housing.
The 231 "dhd" (ive never heard of that) and the sye kit you pictured have clearly different bolt patterns.
NP231D (dodge) HD (Heavy duty) came with the wider chain and I believe most have the 6 gear planetary. I have an NP231D that has the same bolt pattern as is shown in the first pic. Good eye, though.
The D transfer case speedo has a gear that has to be matched to the tire size. I have a gear speedo case with a magnetic pickup screwed where the cable goes from the factory.. They did all kinds of funky stuff.There's several different styles and a year break around 95 or so. They also installed 3 4 5 and 6 pinion planetaries in different cases over the years. They also have a break around 95 with different pitched gears.
The D transfer case speedo has a gear that has to be matched to the tire size.
Most of mine have an external gear ratio adapter. I presume that is so they could consistently put the same gears in the the tail housing.
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