Transmission and differential fluid

A family member has a 2007 Subaru Outback. A week after getting the oil changed, the transmission started making a strange noise. The dealer looked at it and said the people who changed the oil overfilled the transmission fluid and drained the front differential fluid, ruining the transmission. The people who changed the oil claim they did not touch the transmission fluid. What is going on??? Could the diffential fluid have drained into the ATF compartment on its own?

I’ve heard of “quicky” oil change places draining the front differential of a Subaru instead of draining the engine oil, which usually results in a damaged differential and an engine with eight or nine quarts of oil in it.

Why they would add transmission fluid, assuming they had drained the differential by mistake, is beyond me.

It’s not unheard of for the seal between the differential and the transmission to leak, but usually not on such a new vehicle. Is the transmission fluid contaminated with gear oil?

Because the drain plugs appear virtually identical and because they are close together on a Subaru, these mistakes do tend to happen at quick oil change places. This is just one more of the multitude of posts telling about the destruction of someone’s (pick one): engine/transmission/differential/brake hydraulic system as a result of draining the wrong system and overfilling another.

At this point, almost nothing would surprise me regarding mistakes made at quicky lube places.

Not sure whether the TF was contaminated with gear oil.
FYI, this was not a “quicky” lube place but a very experienced mechanic who specializes in foreign cars. I do not believe the mechanic made a mistake (although it is impossible to be sure). Your comment about the seal between the transmission and the differential is interesting. Maybe the seal was faulty?
Thanks a lot.