Mustang differential

The young lady from State College PA who called about her “ex-boyfriend’s” (or should be) Mustang got (unusually) correct advice from you two. Yes, you described the operation of a differential, and how it would leave two divots on an evenly gripping surface, but one divot on uneven slickness. It probably did this randomly, but he didn’t observe well enough.

However, the more important issue is why she is still with a doofus like this.
First of all, he had no right to accuse her of damaging his car. If he understood the operation of the differential he would know it was not damaged. As an engineering student he should have known. More so, he was not being very “boyfriend-ish” in accusing her.
Secondly, his immature habit of “peeling out” of a gravel driveway is causing more damage to his car, and any other in gravel receiving distance, than she could have.

She mentioned that he is a civil engineering student, and her family has mechanical engineers who correctly told her she didn’t damage the car. This brings to mind the old statement (joke?): “Mechanical engineers build weapons… civil engineers build targets.”

I don’t know about the 1990s Mustang, but I remember when cars had a differential that would lock the wheels together–on some cars it was called “posi-traction”. This type of differential would let one “peel” out with both rear wheels spinning. In fact, in the movie, “My Cousin Vinny”, this was how Vinny and his girl friend won the case where Vinny’s nephews were falsely accused of robbing the “Sack of Suds” and shooting the clerk.
Now, even if the Mustang did have this type of differential, I doubt that the slight accident would have damaged the differential so that the lock-up feature wouldn’t work.

Tom & Ray missed the hint - “two divots on his parent’s gravel driveway”. I would bet that this Mustang has a limited slip differential. I would also bet that this Mustang is a GT or 5.0 LX model, which have had Trac-loc rears since 1984. That said, the young lady from State College PA is completely innocent, and the soon to be ex-boyfriend / civil engineering student is guilty. His addiction to accelerate has worn out the clutch pack in the Trac-loc differential. All is not lost, both the car and the relationship can be salvaged. For the Stang a new clutch kit and an apology for the young lady.