[FC] More ? for the masters; 90 weight leak

[Wild8bill at aol.com]

Before I randomly start "fixing" things, I need to get someone's two cents 
worth of info. I have a gear oil leak that appears to be between the 
differential and the clutch (4 speed mated to former powerglide motor). It seams to be 
from the lower half or bottom of the connection. I'm under the impression that 
the differential is a "bath-tub" with no way for the 90 weight to reach a 
joint. Also, possibly related, after the truck gets hot, when going up a steep hill 
or accelerating fast, the motor will race and the speed decreases or stays 
the same (like an automatic thats slipping). Other symptoms: hole plug above 
clutch cable inlet is missing; there is small amount of oil in the clutch inlet; 
no 90 weight leaks from filler bolt or top plate; no dripping until it's 
warmed up, stops after a few minutes when parked, but really comes out when first 
parked (18" round puddle). I need to get someone to watch it, because I don't 
know if it's only dripping when I depress the clutch, or all the time. At the 
rate it comes out, I would think the differential would be dry, and that there 
would be a trail going down the street, but there is still oil left (but 
less), and the only noticeable drips are where I parallel park. Any suggestions?