I've been having problems with my car for the past 5 months... it seems like a transmission problem. when i'm slowing down and coming up to a stop sign or red light... the car jerks/bucks. it's an automatic but it doesn't seem to be downshifting right? i've noticed a whistling noise coming from under the hood that occurs whenever my car runs ****ty like this. (its not constant but most of the time) i can't really think of a way to describe it... but maybe a tea kettle going off??? I just took it to get scanned but AS USUAL the car never wants to act up once i schedule a garage appointment. the scan analysis said the car has no problems. but a couple days after the garage... i drove it a longer distance than usual (only about 65 miles) and it's acting up again. someone suggested a leak in my vaccuum hose?? any other suggestions? thanks!!