1978 C10 305 5.0L Custom deluxe th350 transmission leak
 

My truck is leaking transmission fluid from the weep hole, what should I do? There has been a lot coming out of that hole, the seal on the tail housing is fine. Any ideas?

Re: 1978 C10 305 5.0L Custom deluxe th350 transmission leak
 

There is a seal inside of the transmission tail shaft that is probably worn out. There are different versions of T350, some didn't use a weep hole in the front yoke. When I changed transmissions in mine, I also changed to a none weep hole yoke.

Re: 1978 C10 305 5.0L Custom deluxe th350 transmission leak
 

Welcome to the site. Is the seal new?
Here is info on the seal: http://www.73-87.com/7387garage/drivetrain/yokeleak.htm

Check the vent line is clear. If the vent line is clogged, pressure builds up blowing out seals.

Re: 1978 C10 305 5.0L Custom deluxe th350 transmission leak
 

I noticed a little bit of leaking where the the tailshaft housing bolts on. I read and seen the article above about the cup and O ring. I've read that a l;ot of folk had no cup or O ring? Is that true? I've had my truck in the garage for the winter while trying to wire brush the rust off, so it has been sitting for a spell. I did install a new transmission mount, the old one was wore all the way down, so the new mount lifted the tail housing a couple of inches. I also found a website that offers a plug for that weep hole. I don't know about the vent or how to check it. Thank you, Al