XC90 T6 2004 Flutter Vibration During Idle and Acceleration

[VolvoXC90T6party]

Problem: There is this flutter and course idling when the 2004 XC90 2.9L T6 AWD (139K mi) is in gear (not when in neutral). When I climb hills or accelerate something slips a little. It's not a prolonged slip but a short slip (sometimes it's detectible and other times it's barely noticeable but lately it's gotten much worse at stop lights and during acceleration on highway - this all started about 4 months ago). I am concerned it is a differential, transmission fluid (lack of or bad), or a water pump or a belt tensioner (auto spring). What do you think it is? How can I check? Where should I take it in Jacksonville, FL?

> just changed the battery after six months (the cells were dead).
> check all fluids from engine compartment and they appear to be between add and full (transmission fluid dip stick is accessible from this location right?).
> belts seem to not be worn or cracked
unrelated:
> changed tires, ball joints, and ft and back breaks in last 3 mos.
> original transmission was replaced by manufacturer in 2009 (I think) under extended warranty
> I am the original owner

[rerobin66]

Flutter is a good word for what my 2000 s80 t6 has experienced. plenty of power, and flutter is often barely noticeable until I have to accelerate and climb a hill. I had two or three vacuum leaks (bad or broken hoses, and a pipe that came loose from the ETM) fixing these helped alot but not entirely. I am now waiting on my order of a new intercooler hose, turbo boost solenoid, and a new MAF sensor. If any of, or the combination, of the three fix it totally I will be very happy. If they dont....I can only conclude that it has something to do with the disposable transmission put in the s80, but I am not convinced.