2002 Mercury Mountaineer - Growling Sound

[meyersm15]

Hi All,

First, I would like to say that this site is awesome and I am a first time poster, so if I'm doing something wrong here, please let me know. Now for the specifics of my issue...

I have a 2002 Mercury Mountaineer with very low mileage. 53,000 to be exact. My Mountaineer has the 4.6L V8 and is AWD.

Pretty much since I bought the vehicle, I have noticed a growling / whining sound coming from the front end. This sound is present upon acceleration and stay consistent with cruise control set. If you let off of the gas and let the engine begin to slow the vehicle, the noise goes away for a very short period of time before it comes back as the vehicle is slowing down under its own power. I originally thought it was wheel bearings, so I replaced the driver side hub, but no change.

After a little more thought and some online searches, I began thinking the issue could be somewhere between the transfer case and the front differential. For a little more research, I pulled the front drive shaft out and the vehicle drove beautifully. No noises, no vibrations, nothing. This leads me to believe the issue lies in the front differential, but I really don't understand how the front differential works.

If it is a bearing or something in the front differential, would this be inactive when the front drive shaft is not installed, therefore causing the noise not to happen?

Any help that anyone can give would be very much appreciated! This sound is an incredible annoyance and I am seriously considering a Flowmaster muffler just to try and drown the annoying sound out with a good one. Please let me know if I can provide any other information that would be helpful in the diagnosis of my issue.

 

[Donystoy]

It sure seems to be very low mileage to be having problems with the front differential but indications are that there could be problems there. How is the fluid level? Certainly verify first that the right wheel bearing is fine by removing rotor and caliper and spinning it by hand to check for roughness. Even though the noise went away with the shaft removed it was still a part of the rotating assembly and just it's drag might effect the sound.

 

[meyersm15]

Thank you for your response. I have previously checked the right wheel bearing, and it is in good shape. I have not checked the fluid, but am planning on doing that this weekend. I assume and hope that it is OK because the dealership gave me a service receipt when I purchased the vehicle slightly over a year ago that they had to replace one of the wheel seals and put new fluid in it after they took it on trade.

As I'm typing this, I'm beginning to wonder if this car didn't below to some little old lady and the wheel seal went bad and she kept driving the car with a low fluid level in the front differential causing damage.

I'm just not sure how to tell without taking the front differential apart, but if I were to do that, I'm not entirely certain what I would be looking for. Do you think there would be any value in draining it and filling it up with a high quality synthetic fluid?

 

[Donystoy]

There is a plug in the front of the differential that is for filling. I recently topped mine up after replacing the left shaft and seal. I think it requires a 3/8" ratchet end to remove. It is meant to be filled to the bottom of this hole. If I remember correctly, the specs call for regular 90 gear oil which is what I used. Just stick in a tye wrap end or similar to check the level.

 

[biswrest]

I am getting a similar noise, I took it to the garage and they told me a pinion bearing. I have not had it fixed yet, because they wanted 800 to do it.

 

[meyersm15]

Your issue is in the front end as well? It did some searching on the pinion bearing, and it seems pretty common for that to be an issue with the rear differential. I would like to figure out how to do this myself to avoid such a huge bill, so if anyone has any idea or knows of a write up somewhere, I would love to hear about it!

 

[imp]

Your issue is in the front end as well? It did some searching on the pinion bearing, and it seems pretty common for that to be an issue with the rear differential. I would like to figure out how to do this myself to avoid such a huge bill, so if anyone has any idea or knows of a write up somewhere, I would love to hear about it!

First, you must determine pretty certainly where the noise originates. The most gratifying way of doing this is to place the vehicle up on jack stands, supported under the front & rear suspension, and RUNNING the vehicle in drive while using a stethoscope device to listen to potential noise-producing areas. This is a fairly reliable procedure, but not easily used by the non-technical or poorly-mechanically-inclined individual.

I use a short length of rubber tubing, about 3 feet long, perhaps 3/8" inside diameter, stick one end into my ear, the other end held tightly against wheel bearing housings, differential housings, pinion bearing areas, etc., and a LOUDNESS report of noise production is immediately available.

This process is productive, but risky to the inexperienced. Care must be exercised at all times. But it works. Your original post suggests you are casting about in uncertainty. If you have the wherewithal, try to find out exactly where the noise is originating. imp

 

[meyersm15]

Thanks Imp. I will give this a try this weekend. I'm really leaning towards the front differential for the culprit of the noise I am hearing. It is really the only thing that makes sense, but I will use your recommendation to further prove my theory. If this is the case, I think I'm capable of the repair, but a write up would definitely be nice. Are you aware of anywhere I could get my hands on one for something similar to this?

 

[imp]

Thanks Imp. I will give this a try this weekend. I'm really leaning towards the front differential for the culprit of the noise I am hearing. It is really the only thing that makes sense, but I will use your recommendation to further prove my theory. If this is the case, I think I'm capable of the repair, but a write up would definitely be nice. Are you aware of anywhere I could get my hands on one for something similar to this?

"Front Differential" is still a vague diagnosis. WHAT in the front diff? Pinion bearing, diff. side bearing, gear teeth, diff gears, or spider gears? The listening tube can confirm not only IF it's in the middle, not a wheel bearing or CV issue, but directly under the pinion area, if loudest there, pinion bearing rather that deeper inside the melon. Anyhow, let us know! imp

Edit: BTW, since AWD, no trouble should be experienced if run on jackstands, beyond possible ABS light coming on dashboard due to wheels not turning same speed both sides back or front, because one side always drags a bit more than the other.