I have a 2004 trailblazer with I-6 engine. Truck started to make a jet turbine type noise for about 30 seconds during a cold start (hasn't been driven for a couple of hours). If the truck is started after that no noise is present. I also noticed a bit of a performance hit as the truck seemed to be bogged down. Also it would have a hard time shifting into second during cold start conditions. I changed out the fan clutch assy and the water pump. I started the truck and its still making that noise. I noticed that the truck drives much better now and that the 2nd gear shifting issue looks to be gone. The start-up noise is killing me. Replacement clutch is a BEHR.