Should a Ford dealership cover parts on my vehicle under warranty that were modified by the previous owner?

I bought a 2012 Mustang GT from a Ford dealership about 3 months ago and the car now has a klunking noise coming from the rear that has been determined to require a rear differential rebuild to fix, which will cost a couple thousand dollars. The service tech is telling me that it might not be covered under warranty because the previous owner modified the car by putting in higher gears.

I feel that I bought this car from a dealership, still under warranty, and had no idea about the modified gears, I shouldn't have to pay for this rebuild myself. Thoughts or knowledge?

Ford dealership sold you the car, right? And they are the "expert" on Ford products. They claimed your vehicle was inspected to ensure their high quality standard is met.

Granted, it is not possible for them to inspect every gear and every bolt, it is still true that Ford dealership inspected, passed, and sold you the vehicle. They are the expert. You are NOT. So you relied on their expertise to sell you a vehicle that is good.

If they deny your claim, you should go to corporate and argue. If that doesn't work, you can probably bring a claim (to court) and argue. If push comes to shove, you should pay an attorney an hour worth of time and discuss it. Have him write a letter that you are willing to pursue the matter "vigorously" and send it to dealership and corporate.

If the problem with the rear axle is due to poor maintenance or sloppy installation of non-factory parts by a previous owner, then the dealer is NOT responsible. The previous owner voided the warranty by his actions. The dealer can't just wave a magic wand and make it all better again. You bought a USED car. You've been driving it for three months. It's YOUR car and YOUR problem.