Hi I’m the owner of a standard 6/1972 Datsun 240z, which I recently changed the clutch on (with a new clutch kit) because of an oil leak from the rear main seal. All went well on the install and when I finished I began refill transmission with gear oil (Pennzoil Synchromesh). My owners manual calls for 1.5 liters of fluid in the “transmission case”. I ended up filling the transmission, but it never came overflowing out of the fill plug hole after using 2 bottles (which is roughly 2 liters). Should I continue filling until it flows out or hold off? I should also note I had the transmission upside down for couple of days and small amount of fluid did drain from what I believe is the breather (metal circular piece.) 

Is the car level?  If the back end is high you might have overfilled, the fluid is sitting in the front of the case.  Or if it's tilted sideways, the fill hole might be high.

I've always used less than the capacity shown because of fluid that didn't drain out.  I always lift both front and back end also to keep things level.

Edited July 4, 20204 yr by Zed Head

Does the car still have the original 4 speed?  5 speeds take more as S30Driver points out here.