My sons 85 trans am, that keeps throwing it belt for the alternator.It has the 305 code G motor, with AC, power steering ,alternator and smog pump, and it's has a 4 barrel stock carb. I have look at the alignment on all the pulley,s and looked for anything that might be cutting the belt, all look good. I have notice when we put the new belt on for the alternator it runs for about 3 day's then we start to here a squeal, and I re-tighten the belt.I have marked the bolt on alternator to see if it is coming loose and it looks to be tight. So I am really getting frustrated with the belt coming off for the third time.could it be the belt or am I MISSING SOMETHING. The belt is from autozone it,s a duralast brand.I know new belts stretch and need to be re-tighten.

 

Probably not the belt. More likely, something is in the wrong pulley somewhere; or, some one of the brackets isn't on right, causing misalignment.

The innermost belt goes over the crank and PS, and maybe the WP depending on how many grooves are in your WP pulley. The next one goes over the crank, PS, & AC. The next goes on the outermost (largest) one on the crank, WP, & alt. The frontmost one goes over the outermost on the WP (smallest) and the AIR pump.

Correct alt belt is 7445 or 7450 (7/16" wide and 44½" or 45" long respectively) in some of the mfrs' part # systems, or 15450 (15/32" wide and 45" long) in others.

 

I'm also thinking maybe the crank pulley might be damaged. I have the belts on in that order. When all the holiday stuff is over, I'll recheck the belt alignment, plus I'm think the one bolt on the alternator , upper one may not have a large enough head to hold it tight enough.

 

mine had a habit of flipping and usually breaking the alternator belt about every 5th time I would rev to over 5500 RPM-once the belt held and I found it flipped in the grooves and damaged.Pulleys were all aligned perfectly and turning true...Installed a deep groove alternator pulley meant for early,high revving,1969-72 z/28s and the problem was gone A worn alternator pulley groove can cause the squealing belt. Btw,the LU5/L69 and early 85 LB9 all came with deep groove alternator pulley.