Alternator belt slip

Crusader fixer

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Working on an '83 P30 diesel. The alternator belt, a single 1/2" belt, slips and squeals badly unless severely overtightened, to the point of drastically shortened belt life. Examination shows only about a 30% wrap on the alternator pulley. Applying a stick to the belt slack side immediately stops the squeal even when the belt is less than correctly tightened.
The question: Has anyone else encountered this, how did you fix it? (2) Can an idler be used to gain more 'wrap' on the alternator pully and cure low alternator output, short belt life and squeal?
 

Itali83

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Every square I’ve had has had bad alternator squeal. All were fixed by replacing alternator AND the pulley. A fresh pulley fits the belt better and quiets squeal. Also, I’ve noticed that when the alternators get old and tired, they stop putting out hardly anything for amps at idle. Then once rpms come up, they seem to go full power which instantly puts a load on the belt while rpms are trying to raise and it just creates a situation where squeal is inevitable.

I totally agree that there isn’t enough belt wrap but with new belts, new pulley and new alternator, you’ll be good to go.

I put a 94 amp alternator on my 87 6.2 suburban and with my amplified stereo cranked, a/c on front and rear, lights on and in traffic, my belt never squeals now.

Ben
 

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Every square I’ve had has had bad alternator squeal. All were fixed by replacing alternator AND the pulley. A fresh pulley fits the belt better and quiets squeal. Also, I’ve noticed that when the alternators get old and tired, they stop putting out hardly anything for amps at idle. Then once rpms come up, they seem to go full power which instantly puts a load on the belt while rpms are trying to raise and it just creates a situation where squeal is inevitable.

I totally agree that there isn’t enough belt wrap but with new belts, new pulley and new alternator, you’ll be good to go.

I put a 94 amp alternator on my 87 6.2 suburban and with my amplified stereo cranked, a/c on front and rear, lights on and in traffic, my belt never squeals now.

Ben
You could try a 2 belt pulley from an application that has a ac compressor ride on one groove but just have two belts return. I was trying to setup a 2 belts around ps and alternator and i COULD make it work, but I needed a different crank pulley that didn’t have one of the grooves further than the others from each other (smog?)
 

Crusader fixer

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Thanks guys! I had not considered a better pulley on the alternator. This alternator has recently been replaced and should be good. You lit the synapses and the idea comes to try a slightly wider belt to assure it doesn't bottom out since all power is transmitted on the shoulders of the pulley.
 

shiftpro

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I've brought old slick belts back to life by hitting them with sandpaper while the engine is running. yes it's fun sticking your hand in there, by a spinning fan and all but that's what makes life fun. This is a temporary fix until new belts. And yes if the pulleys are worn a new belt won't do much.
 

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It may also be the brand of belt. Get the wider belt, but get a Gates belt. Dayco is no good. This is especially true with serpentine belts, Dayco sucks.
 

Snoots

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My issue turned out to be that the pulley was spread open more than it should be which allowed the belt to ride low in the pulley.
Cheep fix:
Wider belt. Fixed it!
 

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I've brought old slick belts back to life by hitting them with sandpaper while the engine is running. yes it's fun sticking your hand in there, by a spinning fan and all but that's what makes life fun. This is a temporary fix until new belts. And yes if the pulleys are worn a new belt won't do much.
i thought bath salts made life fun, damnit i was wrong again
 

AuroraGirl

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My issue turned out to be that the pulley was spread open more than it should be which allowed the belt to ride low in the pulley.
Cheep fix:
Wider belt. Fixed it!
cheaper fix, pound on one side of the pulley to shorten the gap, be sure to take belt off so that it doesnt apply side forces on the belt!!!
use a mallet with at least 4lb behind it
 

Chevyguy

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I converted my 87 V20, 5.7, over to the serpentine belt system. I pulled everything off a 92 GMC Sierra 1500. Everything swapped over easily and I now have a 105 amp alternator charging my dual batteries. It is so nice not having to deal with four belts anymore, and the water pump is easier to get to if it needs replacement.

Clayton

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Like Clayton said, Shitcan it, serpentine swap. That's what I did, 6th best thing I've done to my truck.
 

calredneck

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The new belts are not good try sanding the pulleys too and what shiftpro sad
 

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Also, try and clean the surface rust off the groove of the pulley. The rust gets in the material of the belt and causes it to glaze over. Take a brush that you can put in a drill and clean the groove out, but don't mash down on the bristles as it will slik up the metal itself. Just clean it good. And don't paint the groove, that makes glazing worse as the paint gets in the material. Also, check your pulley alignment and make sure everything is straight. A new belt will stretch even though it's adjusted correctly you have to go back after a few days and tighten it again. Adjust to 1/8" of depressing the belt down, as 1/4" is to much. So it's kinda of a particular thing to get it to hold adjustment.

I know, a third wrap seems like it's not much but even with a serpentine if you look at the LS engines it doesn't seem some of the pulleys don't hardly have enough belt on them, but the serpentine does afford more "grip" than the old "V" belts.

I agree with @DoubleDingo, the brand is definitely an issue. You get what you pay for. Goodyear, Gates. NAPA has the Goodyear High Performance belts and they are really good for a "V" belt. They are the best I've used, but they are high so be prepared.
 

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