Hi I have a 1961 MK 9 automatic
Looking in the manual and it shows the gear box cap being in the same spot at the transmission fluid entry point.

Per the manuals instructions, i put 30sae oil into what i thought was the gearbox but it may be the transmission

I cant find much online to confirm that im at the right spot

 

I guess enough time has passed for you to know the results of putting 30 weight into an ATF box.
Im curious though, did you drain it immediately or drive it until it began to slip.
If you drove it how long did it go before it got “Odd”?
Did changing to the right ATF fluid correct it?

 

Sorry, but I'm confused a bit here ! The gearbox and the transmission are the same piece of equipment. What makes you think there is a separate gearbox and transmission ? The drive train for a Mk IX consists of: -
- Engine
- Torque converter (uses the fluid in the gearbox via a pump)
- Automatic gearbox (a Borg-Warner)
- Propeller shaft
- Rear axle

The automatic gearbox would be filled with ATF fluid normal for late 50s/60s auto gearboxes. The engine oil would have been probably a 30SAE oil at the time, with probably a winter option, but most people will now use something like a multigrade like 20W50 or 15W40. Only oils NOT to use are the current very thin oils like 5W30 or 0W30

 

Sorry, It sounded like you put 30wt oil into the opening for filling the automatic transmission.
Mk IX’s also came with 4 speed manual transmissions what a lot of people refer to as gearboxes. Those would use 30wt oil.
Hopefully you did not put 30wt oil into an automatic transmission, but if you did I’d be curious as to what effect it had.