Yes that is a common leak point unless u know when it was resealed I would recommend doing a pressure test and checking all the seals maybe just have the entire drive resealedI noticed a leak coming from shift lever were lower and upper meet....is there a seal gone or is that common
Not air but you will get water in the gear lube turning it milky and potentially ruining bearings and gears. What did you lube look like when you drained it ? Assuming you likely just winterized? If water gets left in ther and freezes can crack the housingOk.....is that possible for air to get it system from that point or no