Odd serpentine belt harmonics?? 2003 spyder GT
 

I have a 2003 GT Spyder convertible with 80k miles on it with the 3.0 engine. When I start this car up in the morning and put it in reverse to take it out of my garage, it makes this loud "growling" noise. When I put it in neutral or park the noise goes away. In forward, it makes the noise but not as much. Anyways when I crawl under the car to find the noise it turned out to be the serpentine belt vibrating. Its not just vibrating, its going up and down about 1/2 of an inch. I've never seen anything like it.
Interesting enough if you drive it to the point where the engine is warm the noise goes away. Its nice and quiet then. Although to be honest I haven't crawled under the car to see if you can see the vibration is still ongoing.

I'm new to this car so I don't know if its been ongoing. I've had the car only about 6 months and have driven it about 1000 miles.

Interesting in the user manual for this car it says that the car will make noise until it warms up but this seems a little odd.

I thank you for your expert thoughts in advance!
David

I would check the belt tension, and maybe replace it.

Actually it is a new belt. I brought the car in and went nuts going through it and replacing things that i felt should be replaced since some things were worn (like the entire suspension). Perhaps I made it too tight, but I'm not so sure..... Its very odd. I own 8 cars and this one is the only one that I've ever seen do such a thing.

The belt should be able to twist 90 degrees.

I figured it out. The idler pully on the serpentine belt chain had failed. The bearings were allowing it to wobble. Anyways, I got a new one from autozone and tightened up the belt, and what do you know, no more bad vibrations :-D :D

i could be sure we had the same question last week...

-edit-
im a moron. Cant edit my own posts??