Glenn you are more than welcome here. I have looked at your builds and you do some great work I really like the BJ and the bear truck. As for the screw drives I posted some good pics on page one with some explanation. I also have a thread on my blue dump truck with some real good pics and info. Here is a link to the dump truck.
Click here If you have any other questions feel free to ask and I will see what I can do to help.
Travis