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Discussion Starter · #1 · (Edited)
On my '96 Caprice:
So when I accelerate hard or "generously" :), the belt slips off towards the back of the balancer. It does not slip off completely. Maybe about 1/4 of the belt moves towards the the timing cover. The belt is fine on all the other pulleys and the tensioner.

I replaced the balancer in March along with a new tensioner because of bearing noise. There was no slipping on my 2000 mile roundtrip summer drive to Chicago either. One day around town it just slipped back and I heard it squeaking. Reset the belt, same thing happened again. Finally it happened and ended up chewing off the outside edge of the belt.

So I replaced my new Goodyear Gatorback tensioner and Gatorback belt for a Gates model tensioner and another Gatorback belt. Well same thing happened again. I figured it must be the belt because I have already done 2 new tensioners. Maybe the Gator teeth were slipping or something?

So I put on a new dayco belt with the standard ribs. After two weeks, it slips off again after a nice WOT.

So what am I missing? I marked the balancer on the inside and outside rings to make sure they weren't slipping, which is how I knew to replace the old one. All good there. If I received two bad tensioners in a row from different makes that would be weird. Plus if it was the tensioner, would it not happen at other times besides hard acclerations or WOT? I am not having any charge or alternator issues either which I think would be indicative of poor tension as well.

TIA
 

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Check all the other pulleys for alignment. Maybe you have a loose bolt on the alternator, acc bracket, or a/c compressor. Use a straight edge to see if their all aligned. My car used to do the same thing at WOT only with the wheels turned, when their straight no problem.
 

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I would guess you did not seat the balancer all the way down. The slightest imperfection on the crank shaft (slight surface rust or even dirt) will make it almost impossible to seat. I broke the balancer bolt on mine trying to get it on. After getting the old bolt out I had to use emery paper to polish the crank snout and no more problems it went on easily. Hope this helps good luck.
 

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Discussion Starter · #7 ·
Wanted to give an update...

When the new balancer was installed, the hub was cleaned and everything seated, bolts were torqued to spec.

All bolts were torqued correctly, none were loose. I checked pulley alignment and everything looks kosher. Gave all the pulleys a spin and they all sounded good except for the alternator pulley. It was a little loud and sounded like something was rubbing just slightly. I stood on the passenger side of the engine and eyeballed the edge of the pulley, and when I spun it I could see the pulley wobbling in and out from the alternator. It would also have a constant squeak when I spun it in the opposite direction.

Threw a "new" alternator on there from Autozone and so far so good. Everything is a little quieter and gave it a few hard accelerations but there was quite a bit of Friday traffic. I will be testing out this weekend to see if the belt will slip on the hard accels.


More than likely the hub is spinning on the crank.
Are you saying that where the hub enters the front of the timing cover and connects on the crank is loose? Wouldn't this produce other very noticeable symptoms and sounds?

If you are sure the balancer is okay, check the crankshaft thrust.
How does one go about checking the thrust without removing the engine?
 

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Discussion Starter · #8 ·
It has been just over one week now since I installed the new alternator. Been driving it around pretty hard the past couple days. Got out into the country roads and did numerous hard throttles.

I have had zero slippage issues since I changed the alt. The old alt pulley had a bit of a wobble to it, and it appears that is what was throwing the belt off. I am pretty confident the issue is now resolved after they way I have been driving it the past week. :)
 
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