Jeep CJ-5 w/304 transplant (I think this now qualifies as a Mopar). Alternator belts squeals loudly whenever I start it up and for the next minute or two. I've changed the belt, I've even changed the alternator. The water pump pulley is original and I can't find other issues. Why is it doing this and how can I make it stop (besides bar soap on the belt)?

Make sure you have the correct belt width. Is the belt riding deep in the pulley?

Obvious questions, proper width belt?

Proper tension?

Alternator spin freely with belt off?

Good questions.

This Jeep sits for 10 months a year ( I only use it for hunting ) so it only gets a few hundred miles a year on it so I've let the alt belt squeal for quite a while (over 10 years) but now I'm tired of it

Correct belt width I believe. It's had a couple of different belts on it over the years and the top of the belt is close to flush with the pulleys outer circumference. I even replaced the alternator a couple of years ago with a new one to verify it wasn't the alternator or pulley.

The volt gauge shows ~12 volts while it's squealing and jumps up to ~14 when it stops, which makes sense.

Tighten the belt.

I've tried multiple levels of "tightness" over the years. I've had that belt tight enough to use as a banjo string and still no joy.

Right now it has very little deflection when pressing on the belt in the middle of the span.

Could be the alternator does not have an exciter. Look at the gauge and I bet the it starts charging when the squeeling stops. If this the case there are a few remedies, Jeep used a red discharge light as an exciter for years.
https://www.youtube.com/watch?v=5l2qro7PLIY

You're correct, the gauge shows it's charging once the squealing stops. I'll take a look at the exciter to learn more about it.

Thanks for the idea.

The squealing is from it slipping. If it was an field excited style it would not squeal as there would be no load at that time. Next time start it rev it up two or three times. Shut it off and feel the pulley for heat. If its hot its slipping. Tighten it some more and see what it does. I guarantee I could have it stopped in 5 minutes. The 304 is hard to get the belt tight.

Check the alignment of the belt.

I'm confident that it is slipping but I don't know why. I thought maybe it was calling for too much of a charge for some reason or ??? I'm not the best mechanic out there and there are a lot of folks in the board that know much more than I do, that's why I ask the questions, but I do know how to properly tighten a belt. In fact, as I mentioned before, I have overtightened it using pry bars and it still squeals most of the time.

I'll rub some more bar soap on in it and call it good for another couple of years

Sometimes a belt dressing will work.

Mark the adjustment slot where the bolt sits. Now loosen it and pry the alternator a little and tighten it. If it still squeals go a little more till it quits squealing.

Does the alt belt drive the water pump too? Could be a worn water pump pulley (or a worn crankshaft pulley for that matter) that is causing the problem. Start it, rev it a couple of times, then shut it off and make sure which pulley is slipping by which pulley is hot. If your trying to fix the wrong pulley, it will never be fixed.

The Jeep I had had a bad crank pulley, it was down where all the road salt attacked it for years. Put a different crankshaft pulley on it and the squealing went away. Gene

Is this a standard Stock application?
Make sure you pulley alignment is good.
I have head there can be some variation on belt angles due to our metric conversion
I have also heard that several have had luck going to a "cogged" belt.
I do know that they recommend taking the tension off mower deck belts when storing for extended periods or the belt will stretch
Give gates a call and pester one of their tech people

keep us posted

I'll verify which pulley is getting hot due to slippage, good idea.

It is a stock setup and the pulley alignment is good.

I'll work it and let you guys know what I find.

Thanks