http://members.shaw.ca/bonneville01/MVI_0003.avi

Please tell me it'* the alternator. Crap on the acc. belt is vibrating, not sure what is making that sound for sure. Goes away with revs...back to finding my old alt...

Edit: Come to think of it, this is classic harmonic balancer, isn't it?

Sorry to say this, but yes it is the balancer. It'* doing the same mine started to do about a month ago. I just had it priced to fix a few days ago and I was told the part was $200 bucks plus and hour to install at the shop, so around $300.00 to fix. :(

Must be a GM part. Local parts houses have aftermarkey balancers for under $100 though I would not use the ones that say "made in China".

Another alternative is to have Dale Mfg rebuild yours http://www.dalemfg.com/harmonicbalancer_002.htm I just had one done for a 3800 and his gaurentee seems to be lifetime. Runs about $108 including shipping both ways in the US.

Is about a half hour job with the right tools (air impact is most common) and impossible without. Torque spec on the "C" crankshaft bolt is 219 lb-ft. Good news is that it slides on and off unlike the "L" which requires a puller.

It'* the balancer for sure. I can move the acc belt with my hand back and forth, there are little rubber bits under the balancer, and the center of the balancer is not spinning.

Is an impact gun the only way? Is the trick to this to not have the engine turn over? I'm afraid the only thing I have access to is a big breaker bar. Also, does anyone know the size of socket I will need?

Thanks...

Well I managed to changed the harmonic balancer on my new engine to replace the blown one.
I used a 22mm socket on one engine but the other engine was around 1 1/8" socket, not sure why though. I was able to do it with a breaker bar and a long pipe. Mind you my hood was off, so I was standing on the car and started to pull. It broke loose pretty easy, but then again the pipe was about 4-5 feet long. You should be able to do the same thing even with the hood on. Although the method of cranking the engine to break it loose may work, it may also cause other problems ( if the breaker bar gets loose).

You may have to find a way to wedge the flywheel so the engine does not turn over ( I put a 1/2" socket extension in one of the wholes on the flywheel) when you are trying to loosen the bolt. For that you will have to go under the car and take of the inspection cover ( plastic with 3 bolts in it, on the driver side just behind the starter). Now that I have seen how to do it ( tried it to find out) I am now convinced that anyone can do it with a breaker bar, proper size socket, long pipe, and wedge the flywheel.

More questions...

Can this be done using the tool they mention in the FSM to hold the flywheel while removing/installing the bolt? And also...if I replace the serpentine belt at the same time, can I get one that by passes the AC compressor? It doesn't work anymore, so it'* useless to me...will there be any negative side effects from doing this?

That HB remanufacturing place sounds good, but I can't have that much down time with the car...I'm going to try and get this done tomorrow since I'm off all day and have a guy with lots of mechanical knowledge willing to help.

edit: You posted at the same time as me 1990...and yeah, thats what I'm talking about. Something to wedge in the flywheel to stop the engine from turning over...

Never knew about any toll to do it, I used the hole cause I didn't want to damage any of the teeth.

You probably can get a belt that will bypass the compressor, but I am not sure what size you will need for that. I ran my car for about a year with a compressor that no longer worked, the rear housing leaked and let the freon out.

Got it all done today...it wasn't too hard at all. Here is a step by step for future victims.

1. Jack up the front end on both sides and but the car on jack stands.
2. Remove the drivers side tire.
3. Slide the coolant overflow bottle off and move it out of your way.
4. Remove the feder splash shield...it has three clips holding it on. Just pull them out.
5. Remove the accessory belt.
6. Remove the small shield over the gear teeth...it'* right next to the oil pan, and it'* made of plastic...mine had 2 bolts holding it in. I decided to try it this way since it literally took 2 seconds to get off.
7. Now, I used a large box end wrench with a little dip in it, which allowed it to fit perfectly on the bolt for the balancer. I then took some spare exhaust pipe and put it over the wrench. Have some one stick a flathead screw driver in gear teeth, and have at it. I broke it loose on the 2nd try.
8. Now you have to get the balancer off. Try sliding off the crankshaft by hand at first, and tap it around with a hammer a bit. If this doesn't work, you have to use a puller. Luckily, I had a puller available and I needed to use it. You will have plenty of space to attach it down where you pulled off that splash guard.
9. Lubricate the new pulley with motor oil around the part that slides onto the crankshaft.
10. Slide the new pulley on so that the key lines up and it fits in nice. My new harmonic balancer came with a new bolt, but I used the old one.
11. Torque the bolt down to 219ft-lbs.
12. Put everything back on that you took off, but in reverse order .

My new harmonic balancer was $179.99 CDN @ Part Source. It is made by Dorman. I know you advised against aftermarket replacements, but the genuine GM ones in town were just too much, and I couldn't wait for it in the mail. I need the car. The replacement I got does have a lifetime warrenty, so I can sleep easy. She rattles no more.

you forgot about trying to wedge a deepwell socked in the power steering pulley to try and stop the engine, warping the pulley

With how tight the bolt is on the HB, the belt would just slip on the PS pump. Even I wouldn't try that, lol.