Auto Parts: S10 starter breaking / kickback, auto parts store, back fire

Question
Mike  Thank you for the quick response to my question.  I will have a shop connect a real time recording engine analyzer as you suggested.  The ring gear has lost a couple of teeth in on spot so that has been replaced also.  I do not know if the first starter was full size.  The replacements are much smaller.  I do have a original equipment unit that came from the same truck as the donor transmission that was recently installed.  Would that starter fall under the same small category?  The motor seems to kick back when cranking will cold.  I have never heard an actual back fire through the intake.

Answer
    You really don't have a choice between large and small starters, you have to use what belongs in there.  I wonder if it's possible that you used the wrong replacement ring gear, or the wrong transmission.  Also, it's possible that there is a spacer missing.  In older vehicles the starter had to be shimmed until it performed correctly.  Most really new vehicles don't require this any more, but yours might.  An auto parts store or a dealer should have the shims if they are required.  Due to the willy-nilly replacement of the parts in the system, I'd be willing to bet that shimming is the answer.