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and my first issue is a started that grinds horribly on starting. it was fine a day ago today it grinds like there is no tomorrow and when watching it under the car while a friend turns the key it jumps all over the place. bolts were still tight so im thinking in this order.
1 dead solenoid in the starter is not allowing full engagement.
2 bent the mounting bolts and allowing starter to wiggle
3 broke the shaft in the starter and its only turning the flywheel by chance
St. Jude Donor '05-'06-'07-'08-'09-'10-'11-'12-'13-'14-'15
If the starter is jumping all over the place when your friend turns the key, the starter is loose. It may be that the starter was shimmed and a shim or shims have came out and now the starter is Jumping like you say.
I would start by trying to get the starter mounting bolts tightened down. They are probably frozen in place and need to be worked loose so you tighten them correctly. Disconnect the battery before attempting to work on the starter. You can easily do some welding down there with wrench in the wrong place accidently.
Only one way to find out... remove the positive cable from the battery post, get it in the air and take the two bolts which hold the starter in... out. Remove the positive cable and solenoid cable and look things over in there. Are the cast bosses on the block broken? Are the flywheel/flex plate teeth all chewed up? Report back with what you see please.
Don't forget that the starter should have a brace from the block to the front of the starter also, a lot of times these are discarded when starters are replaced. Probably still available from GM or: http://cgi.ebay.com/ebaymotors/START...=p4506.c0.m245
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