Which alternator do I have?

[Popcorn W]

03 2500HD 4x4 with 6.0
My alternator is making noise and I need to replace it, but all the parts books call for either 105 or 145 amp. How do find out which one I have?

[gmclowsierra]

it should be stamped on the case. sometimes its a little hard to find. I would just put the bigger one on. it wont hurt anything just more amps.

[Popcorn W]

Originally Posted by gmclowsierra

it should be stamped on the case. sometimes its a little hard to find. I would just put the bigger one on. it wont hurt anything just more amps.

Thanks. Yea, I was wondering if I could just change out (or keep) the bigger one. Might help out since it has a snow plow. I assume they both use the same existing bracket?

[69gmcc10]

From what I can find researching this they both mount the same. I know when I installed electric fans on my 03 Silverado the guy I bought the harness from asked what alternator I had and when he found out it was the 105 he recommended I at least upgrade the pulley to the 145 pulley because it is a smaller diagram, so it turns faster and starts charging sooner.

Get the 145 especially if you abuse your battery.

[Popcorn W]

Originally Posted by 69gmcc10

From what I can find researching this they both mount the same. I know when I installed electric fans on my 03 Silverado the guy I bought the harness from asked what alternator I had and when he found out it was the 105 he recommended I at least upgrade the pulley to the 145 pulley because it is a smaller diagram, so it turns faster and starts charging sooner.

Get the 145 especially if you abuse your battery.

Interesting. So, the 145 has a smaller diameter pulley? If so, it should use a smaller serpentine belt then, right?

[69gmcc10]

It is not a big difference, just a few millimeters, but I did go to a smaller belt. The stock belt worked fine but it was at the outer limits of the tension adjuster, probably because it was an old belt. I THINK the next smaller size was from a 97 454 pickup and it was at the tightest acceptable position on the tensioner.

[Popcorn W]

Wanted to share what I found out, so it may help someone else who's looking for the same answer.
I got this from Advance Auto Parts online "ask a question"
There is a sticker in your glove box with a series of alphanumeric codes on it. Scan over to the codes that begin with "K". The code for the 105a alternator is "K68" and the code for 145a is "KG3". Purchase the alternator accordingly."

[69gmcc10]

Originally Posted by Popcorn W

... Purchase the alternator accordingly."

Well...That doesn't sound very fun or hot rod like.

Definitely the safe choice!