Title. To elaborate more, I had my 2005 mustang gt inspected by a mechanic shortly after buying. He found that one thing that needed fixing was a small leak from the pinion seal in the differential. I ended up buying a duralast pinion seal and royal purple gear oil and had him do the job. Simple enough. A week after the repair goes by with moderate driving and the leak seems to have stopped. No more spots on the driveway like before. All of a sudden, yesterday, my car starts making a horrible grinding noise. Like a metal on metal scraping sound. There were no noises whatsoever before yesterday, it came on extremely sudden. I take it back to the mechanic and we find the brand new pinion seal is leaking and the differential is almost empty. He tells me I need a new differential now.
My question is: how do I prevent this from happening again? Obviously I will never buy aftermarket seals ever again, (I know I’m an idiot for that) but other than that, in terms of symptoms, there were no obvious warning signs until it was too late. The car went from running perfectly fine one day with no noticeable leaks or noises to the next day making a horrible scraping noise and by the time that occurred and I took it to the mechanic the differential was ruined. I also hadn’t seen any spots in the driveway that would have indicated a leak so what I’m guessing happened is that the seal started leaking very rapidly over the course of one day (yesterday) probably WHILE DRIVING, and not while parked, hence me not noticing any oil spots in my driveway to warn me the seal was leaking. Again, the car wasn’t making any noise before the grinding suddenly started. Not even a whine. I specifically remember yesterday in the afternoon I was running errands with the windows rolled down and no noises at all. Then later that night when I was driving home on the highway from my friends house it was making the scraping/grinding noise. It did not come on gradually. So essentially there was no indication the differential was almost dry before it was too late.
Did I just get extremely unlucky? Or am I missing something.