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Original Pulleys are the issue, as we can't (at least easily) buy the correct
belts for them. I finally got sick of the noise and put CVF racing pulleys
on because they use the same belt size in both grooves. Using the old pulleys
if either of the belts does not sit in the groove at the same depth as the other
then you have a rotational mismatch and therefore a squeal.

["QUICK-SILVER"]

Originally Posted by 67gtospud

Could you list the part number for the alt. Belt? I'm having this same issue and this makes the most sense. No squeal till I get around 3k.

Reading through this thread might help on finding the right (or close as you can get) belt size.
http://forums.maxperformanceinc.com/...d.php?t=795159
The chart Kenth posted shows 3/8" for alternator and 1/2" for power steering.
http://forums.maxperformanceinc.com/...3&d=1473752579
The belt companies doing consolidating to make more profit and chain store part reduction...we end up with a 15/32" belt for alternator and 17/32" belt for power steering. Right would be 12/32"(3/8") and 16/32"(1/2"). So factory was 1/8th difference between the two and the new after market is 1/16th difference. That's not much till you think about the different belt speed it causes and why it's worse with higher RPM's.

I ended up going to an electric motor company that did industrial work in mills.
Had to tell them width and length I needed because they had no way of looking it up. Got good industrial quality belts for less than half what the part store charged for junk.

Good luck trying to get the right stuff.
Clay

[R68GTO]

Purchased at a local CARQUEST. He had to order them based on the specific info I brought him on width and length required for my car per the shop manual. His original selection in his lookup book showed him two belts of the same width. I insisted that he match up what the spec.s for my car stated. He ordered Dayco belts as it's shown on the invoice but the belt jacket has a Gates logo. 2nd photo shows how the belts ride in the stock pulleys. There was a noticeable difference when the belts were the same width.

[Old Goat 67]

That is the correct fix.

[67gtospud]

I currently had a 15510 from autozone which is .41" wide and 51" long for my p/s pump. (This is what they list for my car). I also had a 257475 from Napa which lists as .41 wide and 47.5" long for my alt.

Based on this discussion, my squealing issue was due to my belts being the same width, So last night I did some searching around on the Napa website. The 15470 lists as a 3/8" belt and the 17510 lists as a 1/2".

Of course neither of these belts were in stock so I called my local Napa today and asked the parts guy to order these part numbers. He said he could they'd be in after noon. So I went and picked them up. . .

Well the parts guy forgot to order the 1/2" one. So I just took the 3/8 one. Went to put it on and I realize the part number is the same as the one I currently had. (25747x). So now I'm a little angry and go back to Napa. I tell him that was NOT the belt I ordered. He says he cross referenced the part numbers and that's what came up. I pulled up the specs for 15470 and 257470 and showed him they were different. He argued with me that it was the same. Then he asked me what car it was for and told me the computer showed the belts being the same width although I brought my service manual with me and showed him otherwise. After about 5 minutes of going back and fourth I told him where he can shove his computer and told him exactly what I needed for belts. He ended up having a 1/2" one in back but could not find any 3/8" belts in his book at all. 13/32" was the smallest which is what I have.

I put the 1/2" belt on the p/s pump and most of the squeal went away but still slightly there on quick revs past 3k.

[STEELCITYFIREBIRD]

If you want true 3/8" and 1/2" belts 3L#'s are 3/8 and 4L#'s are 1/2 ".

Example if you want a 1/2" 51.5" belt 4L515.