When pulling an alternator, how do you figure out what you are pulling? Everyone says get one from this that and the other V8 ZJ, 318 Durango V8 Dodge something etc...When I look up new alternators trying to figure out what the spec is for the various recommended vehicles, they all default to 90 amp. How do I make sure I am not wasting my time pulling the wrong one at the JY? I want to upgrade the alternator in my 96 XJ, I have read numerous posts and watched several Youtubers make the swap, nobody says how to know for sure what you are pulling. I am going to upgrade since I'll be getting a better battery and adding lights and a winch to my build.

 

If it's an aftermarket there will be stickers on the alt that indicate the amperage and part number. If you can tell the brand (Napa, Duralast (Autozone), etc.) and the part number is still legible, you can look up the part on the website and see what it goes to.

However, if you're planning on building up the truck, why mess around with pulling an alternator from the junkyard? You can easily pick the upgrade one that you want and go get a nice shiny new (or newly rebuilt) alternator from your favorite parts retailer and have peace of mind and possibly a warranty. Pulling one from a JY seems a whole lot of work and uncertainty just to save $50-75.