Differential or transfer case failure on the 2004 Mercury Mountaineer
2 crashes 1 fire 3 of the 22 reports for this failure mention a crash, a fire, an injury or a death. Those are the owner's words on the complaint form, not a verified finding, and one report can mention more than one.
When differential or transfer case failure gets reported
Owners of the 2004 Mercury Mountaineer report differential or transfer case failure at a median of 80,000 miles. A quarter of the reports come in before 55,000 miles and a quarter after 90,000 miles, from 19 reports that carried an odometer reading.
A part like this is normally expected to survive 110,000 miles. It is the 4th most-reported problem on this model year.
The mileage distribution
The reported range runs from 30,000 miles at the tenth percentile to 130,000 miles at the ninetieth, a spread of 103,790 miles across the middle 80% of reports.
When the reports scatter this far, the mileage is telling you about how these cars were driven more than about the part itself.
16% of the dated reports were filed under 36,000 miles.
The whole distribution
| 10th | 25th | Median | 75th | 90th |
|---|---|---|---|---|
| 28,434 miles | 56,250 miles | 78,000 miles | 91,000 miles | 132,224 miles |
Read the 10th percentile as “one report in ten arrived this early”. Exact figures are shown in this table because it is the table of record; everywhere else on the site they are rounded to the precision the sample can carry.
What a percentile can and cannot tell you here
These five numbers describe the readings owners gave, in order. The median is the middle one: half the reports arrived below it. The 10th and 90th are the edges of the bulk of the distribution, and the distance between them is the part worth reading. A tight spread — say 70,000 to 95,000 miles — points at something that wears out on a schedule, and the schedule is knowable. A wide one, 20,000 to 190,000, points at a fault that hits some cars and never troubles others, which means the mileage on the listing in front of you tells you very little about your odds.
What these figures are not is a survival curve. Every reading here comes from a car whose owner filed a complaint, so the sample contains only failures: it cannot say what share of the fleet made it past 150,000 miles untouched, because those owners had nothing to report. Nor is the mileage the moment of failure — it is the odometer reading as recalled at the time of filing, which may be weeks later and is sometimes rounded to the nearest ten thousand by the person typing it.
Percentiles are shown at all only once 8 readings exist for the vehicle and mode. Below that the middle of a handful of numbers is noise wearing a decimal point, so the figures are withheld rather than dressed up.
What happens, and what it costs
Of these reports, 2 a crash and 1 a fire are mentioned. Owners write their own complaints and the agency does not verify them, so read this as what the reports say happened rather than as a confirmed count.
Putting it right typically runs $900–$4,200 at an independent US shop. That range is an editorial estimate held in this site's failure-mode catalogue, not a figure from NHTSA, and it is a repair cost rather than a diagnosis cost.
The same failure on other years
The same failure is reported on 4 model years of this car. It shows up earliest on the 1999, at a median of 65,000 miles, and latest on the 2003 at 90,000 miles.
By volume the 2002 carries the most reports, with 23; the 2004 has 22. A mode that appears across most years of a model is usually a design choice rather than a bad batch.
If one year stands out to the left, that is the year to avoid; if the whole line sits at a similar mileage, this is wear rather than a defect in one production run.
Tick median reported mileage Solid middle half of reports Faint 10th to 90th percentile Colour how bad the failure is when it happens
What owners wrote
Verbatim from NHTSA complaint narratives, trimmed for length. The mileage is the one the owner gave.
We put two new tires on the front of the vehicle in july 2006 on our 2004 mercury mountaineer AWD. In dec 2006 we took the vehicle into the dealer south hills lincoln mercury for a transmission problem and state and emission inspection. The dealer fixed problem with transmission, and did inspections. Then two weeks later,on new years eve, we broke down. Vehicle was towed to nearest ford dealer in bedford, pa. The bedford dealer said due to the different "circumference" of the new tires on the front and the older tires in the rear it ruined the differential and transfer case on the highway. Our manual states nothing about this only says to put on the same style and type of tire which we did. They said the circumferences of the tires can not be more than 1/4" different. The factory rep says if we would have taken the car to the dealer for tires they would have told us this. They are blaming the tire dealer for not knowing this tolerance. The tire dealer says 1/4" tolerance is ridiculous. The cost of the repairs and rental car is over $5000.00 south hills lincoln mercury in pittsburgh was going to honor the warranty secretly for me…
Whining noise coming from rear end (rear differential) of vehicle. It appears that ford motor company is aware of this problem but are not willing to repair this issue for free. This problem is widespread, over many model years. *tr
Our vehicle was purchased in june 2008 at dealership nearby. We were driving home and there was a grinding and popping sound in the rearend of the vehicle. It was me , my husband, 3 mth old and 2 yr old occupying the car. My husband got out of the car and stated to get the babies out of the car in a hurry it was on fire. We got the babies out and ran in to call 911 and the fire dept. The fire was contained and took to a local garage at that time I contacted my auto insurance to see if this was something that would be covered. They sent an auto adjuster out to look at it. Our insurance did help to repair the rear differential. The rear differential had got so hot it exploded causing the fire. Then after the car was repaired we began to have problems again at that time I contacted ford motor company. They explained they could not replace the car but if I took to a local ford dealer for diagnostic they may consider repairing. So I did and the whole transfer case has to be replaced and ford is not paying for the cost. I just don't want this experience to happen to anyone else and to risk their lives just driving this car as a result…
Also reported on the 2004 Mercury Mountaineer
Liftgate, tailgate or trunk failure
Other powertrain problem
Other body or interior problem
Cruise control failure
Other electrical problem
Misfire or rough idle
How far this goes
Complaints are voluntary, so 22 is a floor and not a count of affected cars. Mileages are typed in by owners and cluster on round numbers. And the mode itself is assigned by software reading the complaint text, which is reliable in bulk and fallible one report at a time.
Questions this page answers
At what mileage does differential or transfer case failure happen on the 2004 Mercury Mountaineer?
Across 19 owner reports that included an odometer reading, half were filed by 80,000 miles. A quarter were filed before 55,000 miles and a quarter after 90,000 miles. These are the mileages owners reported when they complained, not a prediction for any individual car.
How common is differential or transfer case failure on the 2004 Mercury Mountaineer?
22 reports have been filed with NHTSA, about 1,048 per 1,000 vehicles. Complaints are voluntary, so this is a floor rather than a count of affected cars.
What this is and is not. These are the mileages at which owners chose to complain to a federal agency, which is not the same as the mileage at which the part fails on every car. It skews toward failures that happened outside warranty, cost real money, or frightened someone. It is still the only public dataset that carries failure mileage at all, and the shape of a few hundred readings is informative even when a single one is not. Methodology · JSON · this failure on other cars
Source Owner complaints and recall records published by the US National Highway Traffic Safety Administration, model years 1996–2027 Figures rebuilt Published by AtWhatMileage How every figure is computed