What size Alternator do I have?
 

I got my new truck home yesterday and it needs a belt to the alternator. I looked it up on line and it asks what size the alternator is. Where do I look for this information on the truck?
Its a 86 f250 4x4 ext cab with 460 and no A/C, auto trans.
I would use the old belt, but it is missing.
Is there a tag or sticker somewhere?

It should be a 60 amp alternator, but a 70 amp was also optional, probably if the truck had A/C.

Just take your old alternator off, and go to CarQuest and ask for a replacement 60 amp alternator. If the replacement is too small, your truck has the bigger 70 amp alternator.

There is a production stamp on the top or the back of the alternator indicating the amperage your alt. will handle.

Lariat is right about 60 vs. 70, but find the stamp on your specific component and it show the number followed by the capital letter A:
for example: 60A - for 60 Amps; or 70A - for 70 Amps.

Hope this helps.

The guy just needs a belt, not an alternator.

To the OP, it should be stamped on the case of the alternator. Worst case just tie a string so it fits around the pulleys and measure that. Belts are normally sold and marked by width and length, so it should be easy to see which is correct. Odds are you have a normal small case alternator (65 amps or less).

I imagine the 2 belts it calls for are real close to the same size, good chance either one would work. I'd probably just buy both and return the one that doesnt fit as well.

I realize he doesn't need an alternator, cadunkle. He needs an alternator belt, and depending on the alternator size, his application uses one of two different belts: one fits a 60 amp alternator, the other fits a 70 amp alternator. I couldn't find any stamp on the case of my alternator when I replaced mine a year ago, so I just took the alternator with me and the 60 amp version is what mine turned out to be.

Since you don't know what size your alternator is, you will still have to look at both available alternator belts to see which one fits. I don't think the belts have a measurement size on the packaging. Sometimes the belt sizes can be pretty close, and it is hard to tell what size is actually needed just by looking at them. That is why I suggested taking the alternator with you so that you may first find out what size alternator you have, then you will know for sure what the correct belt is.