my MIL 07 FJ with a tear diff that has been replaced within past 9mo is making some proportionate to speed noises. Folks she asks says it’s road noise from mismatched tires but I’m not certain. I had it out on some snow over Christmas and the noise persisted. I assumed it would diminish noise if the friction tween tire and road was decreased? It never made this noise before, and she’s super wishy washy with what I would call important maintenance, so I don’t know if it’s something as simple as low gear oil or a 4wd component wearing?