Looking for the plastic nut for the top transmission plate (alternate fill hole?)

Just to get started.

I have looked at a T-150, T-18A, and a T-15 transmission diagram, all of which were available in a '78.

I'm mainly trying to focus in in a shift tower having the reverse switch mounted on the rear like in your pic.

A better full pic may help, it's possible this might be a modification/ or substitution.

Do you know what its full description is?

Three speed or four speed?

Unlike a lot of the vehicles that come here, this one is forty-three. Years old, still going like mine!

Parts are still available, sometimes hard to locate, manuals for them are not as high tech as for newer rigs.

I have spent a good while looking at the web for each transmission "images" with little luck so far. More info might help along with some pics.

I do not feel like that it is a fill hole, as most transmissions for CJs fill on the side and are deemed "full" when the gear oil starts coming back out of the fill hole. Checking this randomly at later times is check it cold and to remove the fill plug and it starts to run out, quickly reinstall the plug. (Not digging around with your pinky and feeling for it!)

I did find this diagram for a T-18A, with parts/ pieces maybe popped loose and missing from your plug? It may have used to be this breather shown in the diagram. (Or not).

I'm wondering if it is a tapered plug, or a straight threaded plug? Is it shouldered to control how deep it goes in the hole? Plastic? Might a metal plug work without internal interference?

Send more info, I'll keep looking too.

The Medic

That is a "nothing" hole on your Jeep. That top cover was common between a few brands that used the T-18 transmission, and the hole was for an optional lockout on the transmissions that had granny gears. The idea was that unless you were stationary and released the lockout you couldn't go into low gear, I've only seen it used on a few of them installed in Fords. I guess you could use it as a fill hole if you wanted to, but it just needs to be closed. If you can remove the rest of the one you have you can install any type of shallow threaded plug, you wish. I don't recall the thread size, but it wasn't anything exotic. Most of the later versions just have the plain cover without the hole even there. I would probably remove the old plastic, then just find a plug to fit it, an oil pan drain bolt in the same thread size would likely work, you might need to cut the threads down some though, so it doesn't hit the rail.

You might find a nylon one at a farm or plumbing supply if you wanted to stay with plastic but it's not really needed, and it might crumble like the one you have.

You are welcome.