1995 GMC Jimmy Harmonic Balance

Here I am again asking for help. I have a 1995 GMC Jimmy. Notice when I get belt slap which is a clacking sound that the belt is not riding on the bottom pulley correctly. It appears to be about a quarter inch off. Clacking eventually stops. Then as I drive and full temp is reached there is a constant chirping. The tensioner appears to be doing its job. I marked and observed according to AutomotiveForum help last time. My garage is telling me that it may be the harmonic balance. This all started in March with the replacement of the rear main seal by this garage. I have been through alot and so have they....Can you help? Please explain harmonic balance too. I am trying to get schematics.... Thanks, doccar.

Did they try to replace the front crankshaft seal? There should be no reason for them to be touching the front of the engine for the rear main, unless they forgot which seal was to be replaced, or are trying to scam you. If the harmonic balancer was pulled just a little, and not put back again, then it would be out of alignment with the rest of the pullies, causing your belt noise. If it started making noise right after you got the truck back in March, then obviously the harmonic balancer was pulled a little. If it started making the noise progressivily after the rear main was done, then check and make sure the main bolt in the center of the balancer is not loose. If it is, get it fixed and tightened right away, as if you leave it that way, it will eventlly come off, along with the balancer, and destroy your engine.

If the belt was removed/replaced, sometimes it doesn't get back onto the crank pully correctly. It might be off a grove and will operate that way, not well but it will work. Try releasing the tension on the belt and slipping it back onto the crank pully correctly. If you haven't damaged the belt that should take care of it. If you have been driving very long this way you may have damaged the belt and perhaps you should replace it just for grins, it's cheaper than a tow truck ride.
The chirping could be an indication of the belt delaminating, the groved friction materal separating from the reinforced backing. Again a good reason to replace the belt. If your mechanic removed the belt, he should at least spring for putting the new one on correctly. Don't let him tell you the belt is $40-$50, they are around $20 at Rockauto.com. Make sure you get the right one, there are 2 possible a K060938 and K060956, that means they have 6 groves and are 938 or 956 cm long. Whenever possible, always buy any parts necessary yourself. The mechanic will double or triple the cost, and charge you to pick them up.
Good luck, let us know what you find
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