QuestionGood Afternoon,
I have a very well-maintained 2001 Mercury Grand Marquis GS with 72,000 miles. It is equipped with the single-exhaust 4.6 V8 and the 4-speed 4R70W transmission with a 2.73 to 1 rear gear. Everything is completely stock (except for a Class II trailor hitch used to pull a 1,200lb total weight utility trailer once each week) and the vehicle runs well.
Unfortunately, the car has recently developed a high-frequency whistling noise very evident from the passenger compartment at all speeds above 10mph, very loud at speeds above 45mph.
Initially, I thought this was a vacuum leak somewhere inside the dash because the noise seemed to disappear when I accelerated (even moderately), immediately returning as I let off the gas. I decided to test my theory by accelerating up to 60 mph, and then shifting into neutral. As I coasted in neutral, I revved the engine, however, this time the noise didn't go away...it only lessened as the vehicle got slower - seeming to be a function of wheel speed rather than manifold vaccum. Then, as I was coasting, still in neutral, I turned the engine off completely, and the noise completely disappeared. Thus, brakes/suspension is now ruled out.
Lately, the noise has gotten louder, and doesn't lessen as much when I accelerate. It seems to be coming from either the dash or the transmission tunnel. A visual inspection of the engine and transmission revealed nothing (all vacuum lines were tight, etc.), and carefully listening to every area with an automotive stethiscope wasn't able to help me track it down. As of late March, the vehicle had no trouble codes whatsoever, and the check engine light has never come on.
The only thing I can think now is that maybe it's a transmission problem. The trans is shifting perfectly, goes in and out of torque converter clutch exactly as it should, exhibits no torque converter shudder, and the fluid looks and smells fine (I do plan to install an auxillary trans cooler though, now that I'm pulling the trailer with the car).
The noise is vaguely reminiscent of a speedometer cable noise I've heard in another car before, however the needle of the speedometer never wavers and the reading is factory accurate.
Any ideas? I have both volumes of the Ford factory Helms shop manuals for this vehicle, and the trouble-shooting tables don't really list any symptoms exactly like this. I also have an up-to-date listing of all Ford TSB's for this vehicle from my subscription to AllData.com's DIY site, and there are no TSB's or Recall campaigns that deal with this symptom.
Any help you can provide would be much apprecaited.
Thanks,
Don Gammill
Marietta, GA
AnswerHello and thanks for the question...I'll try to help.
I would suggest that you put the car on a lift and put it in gear and see if you are able to identify where the noise is coming from. With out hearing the noise...I really haven't found any TSB or related items for this problems.
Erik
