# 66 GTO - Alternator Chatter/right alternator?



## Mikereps (Mar 24, 2015)

My alternator is making a chattering noise that obviously picks up with RPM's. Looking across the pulleys the alternator pulley is maybe 1/4" or so out of alignment with the crank pulley (closer to the fan). The alternator is mounted with all the correct brackets and seated properly. Do I have the correct alternator? 110011 9M 12VNEG. The brackets apper to be square to the block. It's as though the part of the alternator in front of the mount holes extends too far in front of the brackets. Thoughts?


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## Mikereps (Mar 24, 2015)

I swapped outnthe alternator fornthe correct model and it resolved the alignment issues. Chatter apparently coming from water pump. On to that.


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## PontiacJim (Dec 29, 2012)

I can't offer any help on exactly how your alt should be located. Geeteeohguy is the person who would really know how your set-up should be. Same as with the alternator itself. Is it original or a replacement? It is quite possible that if it is a replacement, that it is not exact as original and this could be part of the problem.

What I can input is that I have had pulley's out of alignment, but they did not "chatter." If too severe, they can jump off at high rpm's. The chatter may be a bad bearing, or bearing going bad. Is the belt possibly hitting the small cooling blades on the alternator as the belt passes them due to the mis-alignment? Could this be your chatter?


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## Matthew (Feb 11, 2011)

If I understand what you said, you fixed the alignment issue. Possibly the belt is creating the sound you are talking about. Normally would be more of a chirping sound. Easy to check. Use a squirt bottle with water and spray some on the belt as the engine is running. If the sound goes away temporarily, you have it. Just a suggestion. Matt


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## 67Twistytee (Feb 24, 2014)

If the water pump is making chatter sounds, it could be the impeller making contact with a slipping divider plate. The stainless repop ones don't fit as well as the originals in the 8 bolt pumps. Lots of threads on here about getting the pump and plates set-up right. Go with a cast iron impeller (not stamped) and use original plates if in good shape. Inline Tube makes a repop with a notched center which supposedly keeps it better aligned like the originals.


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## PontiacJim (Dec 29, 2012)

Mikereps said:


> I swapped outnthe alternator fornthe correct model and it resolved the alignment issues. Chatter apparently coming from water pump. On to that.


OK, cool. I must have hit my response just after you added yours.:lol:


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## geeteeohguy (Feb 2, 2008)

Remove the belt(s) and spin the water pump by hand to verify it's the culprit. Could also be a loose or damaged harmonic balancer.


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## Mikereps (Mar 24, 2015)

Awesome feedback guys thanks. I intend to get into it this coming week. Am I at risk if I drive it a little? I am not having any overheating issues. We have some nice weather thru Saturday anyway.


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## 67Twistytee (Feb 24, 2014)

Geetee brings up a good point. You should inspect the balancer and make sure the ring isn't cracked or wobbling. You can use a pry bar or long screw driver to check how tight it is and verify crankshaft has no excessive play. When balancers come apart, bad things happen. 

If it checks out and you isolate the noise to the pump, it can likely wait. Unfortunately you need to drain the radiator to remove the pump and check the impellar/plates. Not hard to do, but requires new sealant and gasket with time to cure before refilling the system.


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## Mikereps (Mar 24, 2015)

I will check the water pump and the dampener for wabble. Where would I look for cracks on the dampener though?


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## 67Twistytee (Feb 24, 2014)

Based on the history and rebuild of your motor, you probably have an updated dampener and its likely not the cause of the noise you're describing. The old ones (pre-'68) are a 2 piece design with a rubber isolator between the hubs. This can shrink or crack over time and allow the outer ring to spin loose. If you pry on it and there's no movement, I wouldn't worry about it. The rings are hard to see because of the radiator unless it's up on a lift. If you have ramps you can try to elevate it to get a good look.


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## Mikereps (Mar 24, 2015)

I decided to check the thermostat and it appears as though it was sticking. When I replaced it and got some positive flow going the chattering quieted to a somewhat tolerable level but it's still present. Based on that I am replacing the water pump. It's quite likely they forgot the divider plates so I want to check anyway. Water pump, hoses and divider plates are on order. 

With the lack of use I am betting the bearings in the water pump have deteriorated. I am seeing that same thing with bushings and some other gaskets. Probably not unusual based on lack of use. I am planning to have a local GTO restorer consult me on where to start and in what priority. 

One question. I cannot find torque specs for the water pump to the housing. Do I also need a sealant in addition to the new gasket?


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## geeteeohguy (Feb 2, 2008)

Dampers crack on the shaft, in or at the woodruff key groove. Need to pull the damper to check. It happens from the damper nut being loose, and the damper walking on the crankshaft and getting stressed. Water pump to housing: not much torque....less than 20 foot pounds.....I just tighten them to 'common sense' tightness (it's an aluminum cover, and it's old). I always use a SMALL amount of sealer on both sides of the gasket, let it set up briefly, and bolt it on. And if I can, let it sit overnight before filling with coolant. Good luck.


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## Mikereps (Mar 24, 2015)

Thanks GeeTee. I'll post results when I get the water pump installed. Hopefully that takes care of it.


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