Diagnose Noise

[Gormy]

I have a 2003 Explorer Limited, 4.6L AWD 3.73 LS rear.

As many others have experienced I also have noise from the rear. Although mine isn't quite the same as what others have posted in these forums. I do not have a whine noise that comes on around 35mph and disappears at 60. Mine sounds like a lot like a wheel bearing. It starts the low rumbling starting at very slow speeds and persists all the way up to highway speeds (I drive about 80mph at most and it's still there). It gets louder with speed and it does not go away when I let off the gas. It's matched to the speed of the vehicle. At cruising speeds it sounds like very chopped tires and excessive road noise.

Now before you go and say that it's obviously a wheel bearing - both rear bearings are tight as can be. There is zero play in the wheels in any direction when on the stands. I worked in automotive for 10 so I know most of the quick and simple tests. I just finished replacing both from wheel hubs, all four ball joints (upper control arms as well with upper ball joints), sway bar links, rear toe arms, rear brake pads and rotors and one brake caliper. I did all that on the garage floor. I had Ford install a rebuilt trans because the old one was experiencing all the early signs of failure. I asked them to diagnose the rear noise but they told me "they won't know if it's the differential making the noise until I replace both bearings to see if that makes it go away." Sorry, $660 on a whim is not a viable option.

So my question: With the symptoms I listed earlier does anyone know if this could still be a bearing that is not showing itself when tested, or one of the several internal differential issues?

Thanks!!

 

[Dave8338]

Could be the inner axle bearings are a little pitted or about to fall apart. It will still be tight at the hub but loose on the differential end of the axle shaft.

That would be my first place to look/listen. Are your inner axle seals all tight and dry or is there a bit of a leak? If you have a mechanics stethoscope, block it up on all four corners, drop it in drive and have some accelerate while you are behind it with your stethoscope.

 

[ponkotsu]

Get it up to speed where it is the loudest. Go on a road where you can turn left to right hard. If the noise gets louder when turning left, it's the right bearing, and visa versa. If it's a bearing it will be very apparent from that test. If the noise doesn't change when turning, it's in the differential, or maybe it's a tire.

My rear bearing was tight as a drum. No play whatsoever. Felt smooth to turn by hand. But it was totally fried. After I pulled the knuckle and half shaft, I could turn the bearing by hand. It was very apparent it was in bad condition. But impossible to feel when still mounted to the vehicle.

If it is the bearing, they are a b-i-t-c-h to press in an out. It's 86mm OD and 47mm wide. Unless you've got a torch, press and maybe a good cutoff grinder, I'd suggest taking it to a pro.

 

[Gormy]

I just put the Explorer in the air to take a look at the rear drive shafts and bearings. As I thought both of the outer bearings are tight as can be at the wheels. The passenger side half shaft seal at the differential does have a leak. Not bad but it is wet. Both shafts have in and out play. Minimal, but I can move both shafts in and out between the wheels and the diff. Here's the part I feel might be an issue. Any feedback would be great - If I am laying on my back looking up at the underside of the truck and push upwards on the drive shafts at the diff end (like I am trying to push it into the third row seat) both axles have play. Not much, but enough - probably a millimeter or two. To the best of my knowledge there should be no play at all. Any up and down play in my mind translates to worn out bearings. Any feedback on where to go from here?