Serpentine Belt

[JohnnyR]

Have a 2005 GMC 2500HD LLY/Allison. Stopped at O'Reilly Autoparts to buy a new serpentine belt. Apparently to identify appropriate belt, one must know what size alternator (105 vs 145 amp) and whether there is a vacuum pump. I'll plead ignorance and ask you guys for advice.

[JohnnyR]

More specifically, does an LLY Duramax have a vacuum pump and how do I tell which alternator I have?

[Kennedy]

You'll have to look at the belt diagram under hood and see which one it is.

We don't stock the w/VP modles, but stock the std and a much better price than most for a super tough belt.

[EdHale]

Mine is further complicated because mine has two alternators.

[JohnnyR]

Label under hood is weathered some but all I see there is a routing diagram, no other labeling other than gas or diesel engine. Is there other info there somewhere? Looked at my original window sticker and it showed no options for an alternator so was stock alternator 105 amp? Which trucks came with vacuum pumps (CA versions) ? Mine was purchased in Louisianna.

[Kennedy]

Actually I had a brain fart here. The LB7 to my knowledge is the only one to ever have a vacuum pump so you should be OK with the std belt.

[Mark Rinker]

Mine is further complicated because mine has two alternators.

If you have dual alternators (like I do) you should order a spare and keep it in the truck.

[EdHale]

You are correct Mark. I should have carried a spare all this time, but....

A few weeks ago I did replace both idlers, tensioner and the belt just because of 100,000 miles. The old belt is wrapped up and stored securely under my back seat.

[SoTxPollock]

You guys that replace idlers and belts just because it hit 100,000. Where's your faith in GM?I haven't replaced any of that and I'm coming up on 200,000 miles. Been carrying the spare belt in the tool box now for over a year, maybe someday...

Little hint, take your cell phone and take a picure of your belt routing before it breaks and keep the picture in your phone. Oh and it don't hurt to photograph the belt part number that is on the belt you now have you know. So when you walk up to that parts counter looking for a new belt, the info will be right there with you.