This does seem to be a problem on the 39x trucks but not too bad on the 2t and 2.5 t trucks,you are correct the ring gear is very narrow and often the speed sensor cuts the truck out before the starting becomes a problem.
Its not a bad job to do at least you don't have to take the engine out.
It is also recommended that the starter motor is changed incase it is sticking,also noticed when ring gear is chewed the pinion on the starter is fine.
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