Can a starter be so worn out that it fails completely turn over an engine? The starter on my '82GT slowly turns the engine or struggles to. It's the same effect as a low battery would give.
I know for a fact the battery is good, I checked all the grounds and connections... or could it just be that the starter is about 17 years old and is tired and worn out?

Also, what year did Ford start putting the gear reduction starters in the mustang? Was it 1994 because I have one of those upgraded, smaller units in my car and I want to know what year to ask for if it turns out that I need a new starter.

 

92 they started putting them in, the ground for the starter goes through the starter case to the block that may be the prob or a worn starter