I have a 2004 T660 with the same problem
It is significantly noisier than my two older sleds
just tore the skid out, but have not seen anything wrong yet Other than there is only 3 rear idler wheels. Everything else I have has four. Wierd
the noise seems to be coming from the front
next step, tear out the drive shaft and check the bearings. I bought sled with 2500 miles on it so it's time to go through everything before winter
just wondering if anybody has a remedy for this.