2007 MCS, automatic. 60k miles. Thermostat housing failed a few months back, leaking coolant all over the affected area.

It was parked all day yesterday, upon starting off in the evening, there was a loud grinding/squealing sound from the front. Definitely around the driveshaft/transmission area, but sounded like it was also causing the brake dust shields to vibrate. It almost sounded like badly corroded/squealing brakes, but I'm almost positive the brakes are not the cause.

We took it for a very slow test drive, and the noise pretty much went away, so we continued home. This morning, I jacked up the front and slowly rotated the wheel. As I'm barely moving the wheel it's making a squealing sound, which I think is coming from the inboard cv/transmission area. I used a stethoscope to try and pinpoint it, and here's what I found:

- quiet at the wheel hub
- noise is noticeable at the passenger side center driveshaft bearing when the passenger wheel is rotated.
- noise is noticeable (about the same volume) at the transmission where the driveshaft enters it.
- noise is noticeable when the driver's side (only) is jacked up, which I felt might rule out the passenger driveshaft bearing.

If anyone has any ideas or suggestions on what else to check, I would really appreciate it.

 

If it were brakes then applying the pedal would most likely make the sound change -- I'm sure you tried it, what did you observe?

If as you suspect you've bearing troubles then I'd go to the dealer promptly for diagnosis and estimate (only!) to see what their view is.

On the optimistic side (and you probably know this already) once in a while a pebble or something will get between the rotor and the dust control shield made of light metal that shrouds much of it on the inside. The first time that happened is scared the bejeezus out of me because it can make VERY scary wheel-speed noises (made me think a wheel was about to fall off!).

Of course once the darned pebble works it's way out, the noise stops - it has happened to me a few times in 170,000 miles and I no longer panic.

I hope that it is that last problem, but from your account I fear that may not be the case.

The one fact that argues AGAINST a bearing failure is that this happened so suddenly. It is my experience that bearings do not behave that way, instead a rumble turns into a groan over a month or more as the situation worsens.

Cheers,

Charlie

 

Thanks Charlie,

applying the brakes didn't change the sound, other than coming to a complete stop caused the noise to stop, obviously.

That's almost exactly what it sounded like, my first thought was that something must be binding/rubbing on the scatter shield. However it doesn't sound like the noise is coming from the hub area, it seems to be a bit more inboard than that.

That's good to know about the bearing failure being gradual too, although hopefully that doesn't point to an internal transmission problem. The transmission seems in pretty good shape, the dealer wouldn't change the fluid but I may try a drain and fill soon.

Unfortunately the dealer can't even look at it until Friday. I will try and get it up on axle stands and look over the scatter shields on both sides more thoroughly.

Thanks again for the help, I really appreciate it.

 

RH inner CV joint, maybe?

Spridget