1) A loud vibration rattling noise when engine was cold and transmission put in forward or reverse.
2) Repeat belt squeel chirping each time accelerator depressed.
Belt spray conditioner didn't help much but inspection found the 4 inch shock absorber on aft end of belt tensioner to be wet and covered with black grit from apparent shock oil leakage. Time to go shopping.
AutoZone sells the Automatic Belt Tensioner Assembly for $49 but none available at warehouse. O'Rileys sells it for $157 (ouch). Pontiac Dealer here in Houston sells the part for $249 (ouch-ouch!) I ended up buying the new part assembly from Advance AutoParts for $67. I also bought a new Gatorback Belt.
Suggestions and headaches: 1) Find or draw a diagram showing all pulleys & belt routing. 2) Use long box end 19mm wrench and pull forward to loosen tensioner and remove belt. 3) Use long box end 17mm wrench to break loose the main bolt that mounts the tensioner assembly. 4)Use 12mm wrench to remove nut at top end of shock absorber.
NOW THE FUN PART: After I broke loose the 17mm large bolt I discovered that the bolt would not come out all the way before bolt head hit the chassis. I ended up using a dremmel grinder and a long file to reduce the bolt head length plus I loosened up the right side engine mount and raised the engine with floor jack to get the bolt all the way out. Once it came out, I discovered the inboard bolt end had a 1/4 inch stubby pilot (no threads). I used a pedestal grinder to remove 1/8 inch of the pilot for the next person that has to pull this bolt out.
Reassembled everything with loctite, put new Gatorback belt on and both the rattling and squeel noises went away. What I thought was going to be a 20 minute job took me almost 2 hours. The manual that I read and the posts on this site did not mention anything about lack of bolt removal clearance and the need to raise the engine to get the bolt out. Just my 2 cents, hope it helps someone else.