Can anyone tell me what this plug is, and what it's for? There is one on each side of the transmission housing.They are small plugs and when I unscrew them, a tiny little bit of dark colored oil comes out, and there is a spring behind it.

I asked the computer robots and got this response. Can anyone confirm that this is true information?

That plug with the small amount of dark oil and a spring behind it on your '51 Ford 8N tractor's transmission housing is likely part of the detent mechanism for the shift rails.

Here's a breakdown of what it is and what it's for:
* Detent Balls and Springs: Inside your tractor's transmission, there are shift rails that move back and forth to engage different gears. To prevent the transmission from accidentally popping out of gear, a detent system is used. This typically consists of a small ball (or sometimes a pin) and a spring.
* How it Works: When you shift into a gear, the shift rail moves, and the detent ball is pushed into a notch on the shift rail by the force of the spring. This "detents" or holds the rail in place, keeping the transmission in that chosen gear.
* The Plug's Purpose: The plug you're seeing is the access point for these detent balls and springs. It allows you to remove and inspect or replace them if they become worn or if there's an issue with the transmission jumping out of gear. The dark oil you see is simply transmission fluid, as these components are lubricated by the transmission oil.

Why is there oil and a spring?
* Oil: The detent mechanism operates within the transmission housing, which is filled with oil for lubrication. So, it's normal to see some oil when you remove the plug.
* Spring: The spring provides the necessary tension to push the detent ball into the shift rail's notches, holding the gear in place.

In short, those plugs are an important part of your tractor's transmission, ensuring that it stays in the gear you select during operation. If you're having issues with your tractor jumping out of gear, inspecting or replacing these detent balls and springs might be a necessary repair.

Travis's AI explanation is correct.

The plug is part # 74-7238 SEAT, Gear Shifter Rail Spring

The gasket is part # NAA-77302A

The spring is part # 79-7234 SPRING, Trans. Gear Shift Rail

The ball is part # 353075-S BALL, 3/8"

The same parts are used on '48-'52 8N's and '53-'64 Tractors with 4-speed transmission.

Thanks Bruce, appreciate the confirmation and part numbers!!

Thanks Travis for replying with the facts. Now I know. Dave

I am curious, too. A close-up of my right side:

I can’t post on this site anymore, but I sent you an email Ed with a picture of that same area on my Jubilee and there’s three holes there that I don’t know what any of them do.
Walt

Take the one out that is behind the brake arm (13) and you will be opening up the transmission to put shift mechanism back in place!

drawing xmission

• Link: https://imgur.com/k72AZfs

I am waiting for an answer. Would help if we knew which model and which year. I am now wondering if my 1952 Ford 8N has those.

Mine is a '51 8N.