Hi everybody! I have this situation with my car. I hear a high pitch sound in my engine bay when I'm pressing the gas mostly on low gears. It happens between 2000rpm-3500rpms and pass 3500rpms the squeel will disappear. I was thinking it was the belt, I was gonna tighten them but I don't have any tool to do it.. so I took it to the shop and they said my belt are tight(which I believe it is because I checked it myself) and would not try to tighten them more because they said that it may break or create more damage to the car if they will tighten the belt more that it needs to which I understand. So they came to a conclusion that maybe its the transmission so they recommended to flush it and replace with a new fluid and include a the SLICK 50, I agreed because I know that my transmission fluid needed to be change anyways(past 60,000 miles already). The thing is when they change the fluid the noise is lessen but it still there, the noise is very little now and still in high pitch. What could this be? How to eliminate this? Thanks guys!

My car is a 2001 Honda Accord Coupe LX 4 cylinder