i have a friend with an 03 mountaineer with a failing rear diff, feels like we've chewed up some gears or otherwise done some serious damage inside, and budget constraints don't allow a rebuild. so i'm wondering if anyone knows what years and models of other fords have an identical diff i could replace it with.

the axle code on the doorframe sticker is D4, and the rig is all wheel drive so matching the ratio is important.

as for symptoms, it was reported to me that it was making some bad clunking noises, and a quick test drive around the parking lot showed that when turning a corner the wheels would lock to each other hard enough to skid the inside tire of any turn. so i assume its safe to say that the gears of the differential are probably missing some teeth, and these floating parts are probably doing damage to the ring and pinion as well, so a replacement seems like the best choice.

online parts stores suggest its just a standard 8.8 ford rearend, but i notice its only a center section with CV axles going out to the wheels because its independent suspension, so i don't know what rigs would have the same mounting and all that.

 

I'm certainly not the expert on this, but the general unit should be the same as the Explorer and Aviator. I'm not sure if it was used elsewhere as well. A salvage yard should be able to tell you that. You will need to take a look at the diff tag again and determine which gear ratio it has. I think both the 3.55 and 3.73 were available, and at least one of those was offered with limited slip. Assuming it's a 4WD Mountaineer you'll definitely want the correct ratio.

-Rod