When searching for a method to remove the breather cap and install a vent on my NV3550 I found this site How To Waterproof Your Transmission - GETAHELMET.COM
. I attempted his method and didn't like the fact that the fitting wasn't interference fit anymore and that it used a variety of metals (possible corrosion). So I got to thinking and looking and thought why not use a vent for the NP231? I also looked at the axle fittings. After spending hours under the jeep trying to figure out how to press it in I temporarily gave up. Now I have my body lifted due to removing weld nuts on the top rear shock it gave me more clearance. I got my micrometers out and measured the hole than the fitting, pretty close but the tapper is pretty steep on the fitting. I got my Dremel out with a sanding wheel and slowly removed some material (very minimal). Then I used vise grips on the fitting so I could hammer on them and press down on the collar of the fitting. It is a tight fit like it should be and looks like it should be there unlike the other method. Below are some pictures of the part and final install picture.