Grinding noise in MKX AWD around 40 mph

[Preston4Jesus]

I just got my 2007 Lincoln MKX AWD. I love the car but it has a funny grinding noise when it reaches about 40mph. Its always at that speed. If you drive in town below that or accelerate quickly on the highway it doesn't do it. Only when average driving at 40mph. Also sometimes the left front wheel makes a noise and the traction Control light comes on. If i turn off the TCS no noise in the wheel but at times the tranny noise is still present. It doesn't feel like a slip so much as it does a grinding or harsh noise. Its hard to describe. Also when I turn hard left from the stopped position it sometimes, usually after being parked for a while, it has a hesitation for a second almost like it would if it lost power or like you pinched the fuel line and then released it. I know this sounds weird but has anyone had these problems.

[WWWPerfA_ZN0W]

Ah, AWD! Makes one think immediately of the PTU as a culprit ... Do you have any warranty coverage on the MKX? If not, I would immediately look into changing out the PTU fluid, because it might have metal shavings in there, but looks like very early stages, so might get lucky there. Check the transmission fluid level & condition also, it should be a healthy pinkish color and free of dirt/grit. The driveshaft may be binding at certain times, do you feel any vibration when the "grinding" occurs?

 

Noise at the wheel can be from brakes or hubs. Does the noise sound more present when turning the wheel left or right? It could be perfectly normal due to sensed wheel slippage. But since you notice it at the same wheel, if there IS something wrong, a wheel speed sensor is failing or the ABS tone ring has cracked.

 

For the hard left turn issue: could be a PCM calibration update is needed, or a valve body or orifice cup servicing is required.