I have a 2002 Ford Windstar LX with a 3.8 engine and automatic transmission, the vehicle shudders when accelerating to pass or speed up, like the feel of a rumble strip on the road or as if you ran over something. I tried to identify the problem by purposefully speeding from a constant speed and it happens pretty regular. If I speed very gradually, it does not seem to be very bad, it is when I accelerate quickly to pass that it is most noticeable. It also seems to shift through the gears a little harsh. I also notice a "growl" from the engine area at lower speeds. I am not sure if this is just characteristic of this vehicle or if I have something that should be checked out. This is a new used vehicle for me, can anyone give me some possible causes for these issues?
Optional Information:
2002 Ford Windstar 3.8
Already Tried:
Should I take this to the dealer or a transmission shop for dianosis?