I am not an expert but have had front differential problems lately on the same 2002 Mountaineer v8 AWD model (mine is the earliest model). The first thing I would do is change the two old tires with the exact same brand and model tire right away. I have been told these differentials are so sensitive that simply having slight diameter differences can really mess with the differentials. Make sure that circumference of the tires is very close and that may solve the pulling problem.
That pop that you are hearing may be what I just had to replace on my rig which was two of the front differential carrier bushings (the metal encased rubber bushings that mount the differential to the frame. You can get under the car and look at the bushings. It was pretty obvious they were shot in mine but I put a jack under the diff and pushed it up to make sure that the popping noise was coming from that. The two I had to replace were on the drivers side. Here are the part #s: F67Z3A443AA (for the lower one towards the back) and 1L2Z3A443AA (for the upper front) again these were both on the drivers side. I have to remove the entire differential (this involved removing the tires, brakes, brake discs, ABS sensors, pulling the tie rod ends and the upper control arms using a pit-man puller, removing the stabilizer bar, removing the CV joints, disconnecting the driveshaft from the differential, and finally pulling the bolts mounting the differential). I then cut the flared ends off the bushings using a hack saw, and pressed them out and in using a ball joint press I borrowed from O'Reilly Auto Parts (I had to use an 1 1/4 socket to drive out the bushings). Do not confuse the parts when installing them. They are very difficult to press out. Believe me I know. I found the parts on eBay for about $64.00. Just look up the part number. The place I found on eBay showed them only compatible with Explorers, but as I am sure you know they are the same. You will want to drain the differential oil first and that stuff is pretty pricey.
Friday, February 28th, 2014 AT 1:27 PM