It's essentially the predecessor to the ball joint.  Here's a couple of good articles from Tom Jennings about working on trunnions on his Ramblers.  
 
 
Todd
----- Original Message ----- 
Sent: Wednesday, October 07, 2009 10:08 PM
Subject: Re: [BaadAssGremlins] Fw: TRUNNIONS wanted
| Ok I admit it. I am stupid. What is a trunnion? Terry |