Number of teeth in starter gear that engages in the flywheel or torque converter
 

Pulled 3 starters at the junkyard to replace one that has a bad solenoid.
Have a 2002 Buick Regal LS with 3800 series II engine.
Found some on 3100 engines and one from a 3800.
My starter has about 10 teeth on the gear that engages the flywheel. Some of the ones I pulled had smaller gears with only about 8 teeth.

Why the difference?

Also one GM Delco starter was slightly longer (about 1/2 inch) than mine and had a small black hollow tube about 1 inch long at the rear of the starter and at the bottom. It fell off when I touched it. Looks like it might be a drain hole in case some water gets in to the starter. What is this really for?http://www.gmforum.com/gm/images/smilies/confused.gif