[wilkin250r]

They are simple mechanisms, the difficulty is the SETUP. They have to be precise and the relationships and clearances set up have to be so exact that an experienced installer will pull it out three or four times to get it right, and an inexperienced will pull it out seven or eight times. You'll be installing shims less than the thickness of a piece of paper, moving components to the left or right literally the width of a hair.

The big thing in the middle that all the gears attached to is called the "carrier" and yours looks to have taken some damage.