That bolt / plug is for putting gear oil in for the universal joint .The 4 spd has the plug the 3 spd I understand the Speedo hole is used to fill
The 3 speed also has a plug for putting gear oil into the u-joint area. It also serves to secure the rear bushing in the transmission case.
Kevin 1951 Chevy 3100 work truck Follow this saga in Project Journal Photos 1929 Ford pickup restored from the ground up. | 1929 Ford Special Coupe (First car) Busting rust since the mid-60's If you're smart enough to take it apart, you darn well better be smart enough to put it back together.
