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Sun Apr 05, 2015

Our Flex has had a noise in the rear for some time now. When we bought it, used, a couple years ago, it had a bit of a noise and it always sounded like tire noise to me. This year we replaced the tires... and if you'll allow me to go off on a bit of a tangent, I ordered them from the Tire Rack, as usual. I ended up going with Continental TrueContact SL. They weren't cheap, but they were not as expensive as many of the good sounding alternatives. My primary demands from the tires were good tread life, and a quiet ride. The Flex was engineered to be a quiet, comfortable ride... I did not want noisy tires to spoil that. Back on topic, after replacing the tires, the noise was still present... and I was quite surprised by that. At this point, given the way that the noise changed (got better/worse) as one side of the vehicle or the other was loaded up during cornering, it really was behaving like a bad wheel bearing... except it didn't sound like any wheel bearing noise I had ever heard. It was almost like the sound of a baseball card stuck in your bicycle wheel spokes, but very deep and rumbling. Some online research pretty quickly revealed that Flexs are prone to wheel bearing problems. The forums are full of people having to replace noisy wheel bearings within 20,000 miles. Some of the noises described sounded similar to what I was hearing. Our Flex has 117,000 miles so I can't really complain about some bad bearings at this point. I ordered a pair of rear wheel bearings (the rears and fronts are actually the same) from RockAuto.com, and one of them was completely seized, upon arrival. Not impressive quality there. RockAuto are wonderful about returns and I had a replacement in a flash.

From what I had read about the procedure for removing the rear wheel bearings, they were held in place by large Torx bolts (I believe I saw T60 mentioned somewhere), but that the bolts were nearly inaccessible due to the ABS sensor rings being in the way. The thing to do, apparently, is to press a torx bit out of its socket, and grind down the rear of it to clear the sensor rings, then use a wrench on the remaining flats of the torx bit. Well I'm happy to say that it was not necessary on our Flex. Our wheel bearings were held in place with regular hex bolts, and there are no rear ABS rings in the way. Our wheel hubs have the ABS sensors mounted into them, but I've no idea what they're picking up on because I see no trace of a sensor ring or trigger wheel. This was still not exactly an easy job, because the car has spent 100,000 miles in New England, and the wheel hubs are aluminum, the bearing housings were corroded in place like you wouldn't believe (or maybe you would, if you live up this way).

Before you attempt this job, verify whether you have torx bolts or hex bolts, and whether you have ABS sensor rings in the way of them. Also make sure you have a socket large enough to fit the axle nut, and deep enough to clear the threaded axle coming through the nut. If you're an amateur machinist, you may find yourself tempted to clearance the bottom of a regular socket... don't bother, I tried that and it just won't work out. You'll need a deep 32mm socket... 1 1/4" will actually be a closer fit, and that's what I ended up using. Even if you have a deep socket, you need to make sure that the hex flats seat fully all the way up onto the nut. The nuts are fairly shallow, and most sockets (especially cheap ones) have a lot of relief leading into the internal hex flats. I took my deep 1 1/4" socket, chucked it into my lathe, and faced the hex end to remove all the relief. That ended up being about 3/16". Without doing this, the socket barely gripped the nut. Here is my deep socket, after being turned on the lathe, so you can see what I mean:

Modified deep 1 1/4" socket

With the axle nut removed, and the brake disc, caliper, and carrier bracket out of the way, the bearing assembly can be removed... in theory. I ended up using a small puller (it was just barely big enough) to put as much force as I could against the bearing housing, and then I heated up the wheel hub (or "knuckle", or whatever you want to call it) with a torch. I also used some good penetrating oil. Be careful of those rubber bushings that are all around, and definitely get your ABS sensor out of the way first. One side only took a couple of minutes of heating before it popped free. The other side took much more persuasion, I ended up setting up the torch with the trigger locked in, pointed at the bottom of the housing, then sat and watched it while I enjoyed a beverage. About 7 minutes later, *BANG*, the bearing housing popped free. Here are a couple of pics showing the puller arrangement I used... nothing fancy:

Ford Flex, rear wheel hub and bearing

Ford Flex, rear wheel hub and bearing, with puller

And a couple of pics showing the corrosion around the bearing housings, the first one is just after the bearing assembly popped loose, and the second one shows the wheel hub with the bearing housing removed, and here you can really see how the corrosion has built up. Be sure to clean up the surfaces really well before installing the new bearings. The new bearings should be a very easy fit within the hubs.

Bearing housing separated, showing corrosion

Bearing housing removed, showing corrosion

We now have a nice, quiet Flex!

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