I just installed a rugged ridge slip yoke eliminator in my np231, everything went fine and then I tried to get the speedo gear in the new tail housing, it goes in a little, but it does not go in all the way, it should sit flush, right now it sticks out about half a centimeter, so my speedometer does not work at all, and it throws the check engine light, which is annoying to look at. Also while the speedo isn't working, its not recording the milage, I don't want to get very long without the miles being recorded on the odometer.

 

its eccentric turn it untill gears mesh .http://www.4x4xplor.com/speedo.html

 

I've had the same thing on a few of those I did. I left the o-ring because I couldn't get the speed sensor housing on with the o-ring on. I left the ring off and permatexed the edge. No leaks on a few of these and it's been a couple years.

 

still havent been able to get it back in the tail housing all the way, heres a picture of how it sits, you can see it doesnt sit flush with the tail housing

 

One thing I heard about was the speedo gear was bottoming out in the new housing, like it wasn't machined deep enough for the gear. I never ran into it though.