Chevrolet Repair: gm 4.3 starter, thrust bearing, crank sensor

Question
my daughter has a 96 s-10 with a 4.3, the motor was rebuilt six months ago. since then she has complained the starter was noisy. the starter failed two weeks ago. and has since burnt up 5 more starters. the computer keeps reading misfires. found the flywheel cracked, from misfires ?, replaced flywheel. replaced crank sensor not sure if it is a gm or aftermarket. checked dist. cap and distubuter appears to be ok. the truck is still burning up the starter after starting just afew times. not sure what to try to fix at this point. do you have any idea's. thanks greg

Answer
Sorry it is taking me too long to answer today.  My son's Hockey team is in playoffs and game 5 of the first round is tomorrow!  I am the Coach, extra practice, busy shop, busy schedule, family man and no limit on questions keeps me busting my butt!!!

 Ok,  I ran into this two years ago with a rebuilt motor causing the same issue.

 You need to check end deflection of the crankshaft for a bad thrust bearing or assembly issue.  Check the tooth pattern on the old flywheel and see if it fades in and out of the teeth like a big lazy 's' pattern.   The one I had in had a defective crank and it was walking back and forth causing missfires, eating starters and flywheels.  Take a prybar near the front of the harmonic balancer and pry in and out and see if the crank walks back and forth (in and out)

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