Several months ago i put a new serpantine belt on my 99' TA and ever since i had a terrible squealing noise coming from my accessory system. Although i had several "EXPERTS" look at the problem nothing ever fixed it. First suggestion was to replace the tensioner pulley, so thats what i did and no change. Next they told me it was the idler pulley, changed it and it got worse + i had the new problem of the idler pully rubbing the bracket its mounted on (actually called the aternator bracket). So i sanded down the back of the pulley and although it stopped rubbing i still had the squeal/chirp. Now im getting pissed and fixin to go buy a whole pulley kit and water pump, which had i in the end, the problem still wouldent have been fixed. So i get on LS1 Tech "the worlds greatest engine tech site" and post my problem. One of the people who posted back used to work for GM (or still does) and brought it to my attention that there was a service bulliten stating that the alternator bracket the idler pulley was mounted to starts to come out of alignment with the crank pulley over time, causing my annoying chirp. Even gave a vin # catagory that i fell into from 98-00. Went to the Pontiac house and had them order me one for $35 is what i think it costed. Taking the old bracket off is a bitch but its only like 4 bolts. Loosen the entire alternator (dont forget the one bolt on the back) and the bracket should almost fall off. The new one had a longer mounting stud where you place the idler pulley. The old one had grooves worn onto the stud where the pulley had been dancing around. Although the new bracket was causing the pulley to (once again) rub on the bracket, sanding the back of the pully down again and using the dust cover from the old stock pulley as a spacer stopped that and now she purrs like a kitten again. A very, big, loud, angry, kittin (runnin those LT's wide open again) . Ive saved my self several thousand dollars over the years because of the helpful suggestions of fellow LS1 owners from this site. Just wanted to say thank you!!!

 

Good job not giving up. Gotta part number handy?

 

yes part number anyone?

 

the TSB covers a mid yr change out of the alternator bracket and idler pulley for 2000......all cars produced after this date have the new bracket and pulley......the PN for bracket is 12563327 and the pulley is 12563326 ......you CANNOT use the earlier style pulley on the later bracket or visa versa......it will NOT work......the only source ( I know of )for a new style pulley is GM or Dayco............PN 89159.......you can get old style pulleys by the boat load anywhere......the new style is more tricky to find.......BTW....if you get GM pulleys they come with new dust caps

 

Tsb 00-06-01-008

 

^^^ what he sed