Transmission Drain Plug

Does anyone know the thread size of the transmission drain plug on a '70 Commando? I'm guessing it's BSW?

I was changing the gear oil on mine and the drain plug feels "soft" upon snugging up. I think if I snug it even a little, it will strip.

Hoping I can do a proper repair if I know the thread size.

Thanks!

I measured my threads on my gearbox shell and believe that the drain plug threads are 3/8 x 20 British Standard Fine.

Peter Joe

Yes, 3/8-20.