I believe the gasket thickness is supposed to be the thinner of the two available thicknesses on the market (0.015).
Getting the non-syncro 4-speed to stop dribbling from the many unsealed orifices is problematic. My truck was leaking out of the bearing retainer weep hole whenever I drove down a steep slope. It has reached somewhat of an "eqalibruim" with fewer leaks when the oil is about 1/2 inch below the fill plug when cold (@ ~50 degrees F). Your issue may be no more than that.
When you get driving your truck, and when operated at speed, oil will most likely seep out of the top cover shift shaft rails, and even out of the shifter base. Before you started cleaning up your project, you do remember the thick accumulation of greasy road grime in that area don't you? I almost think GM engineered the process of utilizing grime to seal low pressure joints, definitely not as tight as modern engineering.
Are you using a gear oil that is okay for yellow metals? There are a few bronze bushings in these transmissions. I am using a GL-1 straight 90 weight in mine.
Last edited by Paul_WNC; 11/08/2015 2:32 PM.
