I was gonna say. putting a quart of gear oil in the trans is an old trick to mask transmission problems when selling a vehicle....
I've even heard of people putting bananas in the gear box, lol. I was wondering though, if the filter was replaced, wouldn't it take more than a quart of fluid to refill? Or maybe they re-used some of the drained fluid?
3" suspension lift, shocks: Rancho 9000, tires 33"x11.5", wheels 16"x8", offset= 0, no front sway bar