Trans Threaded hole top of transmission case?

[Fastcat14]

I have a 76 CJ7 with 4 speed manual and the 258. It’s new to me. Gear oil was seeping up and leaking out through the top of the shifter boot. When I took off the boot I noticed there is an open hole just aft of the shifter linkage. after I cleaned it up I noticed it is threaded. Clearly nothing had been in this hole for a while. Any ideas? Some kind of a vent or breather maybe? There was plenty of gear oil in the case.
Thanks for any ideas!

 

[CJ]

AFAIK - it's a vent hole. You can use any 1/4" npt vent or make your own. The pic below is from a Dana 20 but it is the same idea.

See these posts and threads.
https://jeep-cj.com/community/threads/dana-20-leak.58175/#post-524239
https://jeep-cj.com/community/threads/dana-20-vent.60286/

 

[Fastcat14]

Thanks for confirming. It’s definitely venting through it.
I’ll put something in.
Ron

 

[TeamRush]

If it's not the reverse light switch hole, found on different places on different transmissions, it's the vent.
.
Now, aside from the factory vent, if you do deep water, consider a barbed fitting in that vent hole.
A barbed fitting will allow you to run a hose higher up on the vehicle.
You can also hook up an air source, like from a little compressor (mounted up high) and supply pressurized air to the running gear when in deep water.
.
This keeps the water out of transmission, transfer case, axles etc.
I also pressurize the distributor cap/distributor so it blows bubbles under water instead of drowning out.
.
Just some ideas, use them if it fits your application.

 

[CJ]

If it's not the reverse light switch hole, found on different places on different transmissions, it's the vent.. ~~~

 

[Fastcat14]

That’s a great idea. I got a barbed fitting and was going to put some kind of cap on it. Like the idea of a higher hose. I’ll look for a route. Thanks.