Recently I began to hear a grinding noise when the car is moving. So, I put the car up on Jacks, turned it on and put it in drive. Noticed that only 3 wheels spun (front driver wasn't spinning; that is when I heard the grinding noise). I thought it was a seized caliper at first, but I have no problems spinning the tire by hand. The noise doesn't seem like it's coming from the wheel bearings. Any help would be much appreciated. Also, is that how the awd system suppose to work? While in drive only 3 wheels spin; but when I gas it all 4 spins.

 

With a jack raise your tire/wheel an inch or so off the floor, place a breaker bar under the tire and force the tire move up and down. If you have more than two inches of play your issue is wheel bearings...at least that's how it works with RWD!
Gary

 

How many miles do you have on the G? It might be the wheel bearing. but that is weird that only 3 wheels only spinning instead of 4. Not sure how the X but something might be wrong if all 4 is not spinning.

 

It only has 55k on it. I took the caliper completely off and all four tires spun. But, as soon as I put it back on it locks up again and only 3 wheels spin. However, when I turn the wheel by hand, there is nothing restricting it. I'll probably just take it to a mechanic.

 

I only had two wheels spin on my X when I had it on a lift. The X's have an open diff in the front and back so it is not unusual for only one of the pair to spin. The caliper is probably dragging on the disc a little which is causing resistance so the other wheel is favored by the diff.

 

If you jack up only 1 front wheel on an X, it will turn, but with resistance. You are basically turning the drivetrain through the differential and back to the transfer case. A lot of friction there so it takes some effort.

jack up both front wheels and the wheels will spin easier through the open differential. When you spin one, the opposite wheel will spin other direction.

What is the condition of the pads and rotor on the suspect wheel? As the pads worn? How does the backside of the rotor look? A lot of times when caliper slide pins seize, the backside pad gets pressed into the rotor harder and causes it to wear to the backing plate first.

Wheel bearing could also be a cause. I've found that a bad wheel bearing doesn't always wiggle. I've replaced three bad front wheel bearings on my car and none had any movement. They all internally galled up causing roughness and noise, but were still solid. Best way to idenfity on the AWD (because you can't really spin the wheel without spinning the other side) is to remove the rotor and spin the hub by hand. If it's bad, you will feel it. I found that sometimes you can feel a bad wheel bearing through the open differential on the other side. Basically I had to remove both front rotors and spin both hubs. Whichever felt very rough was the bad bearing, but I could feel it through to the other side. After replacing the bad bearing, this feeling to the other side went away.