Weird Engine Noise coming from 2002 Olds Aurora?

Over the past couple days my Olds Aurora has been making a sound that I fear may be the . The sound is not detected until I reach about 35mph. The faster I go the louder it is, it kind of sounds like it is reving louder almost like a hole in the muffler. The only other thing I think it may be is something dealing with my timing belt. It kind of jerks when the car kicks into the next gear. If anyone has any ideas on this let me know. I do plan on taking it in Monday, but wanted to have an idea before I take it in. We have very untrustworthy mechanics in my small town. My brother once took a car in and was quoted $2k. He ended up taking it to another city and ended up getting it fixed for $150. Please help.