Fluid leak from top vent on transmission case:
This problem was much more common to see on the earlier model years of this transmission but is still a potential problem that can happen. The cause of this problem is the upper channel plate gasket. The channel plate is a larger aluminum plate that bolts over the chain and sprocket assembly and has several fluid passages throughout it. The valve body bolts on top of the channel plate. The upper channel plate gasket has had several revisions to aid against blowout problems and the most recent paper design gasket works well. There is a passage that has line pressure flowing through it and this is just under the vent on top of the transmission case, so when it blows out you have very high pressure spraying transmission fluid straight up into the vent and it can make a big mess in a hurry. This can be repaired in the vehicle by lowering down the transmission and removing the side cover, pump, valve body, and finally the channel plate.
Recently the aftermarket has released a Metal design channel plate gasket set which should eliminate any leakage problems as long as the case and channel plate surfaces are in good condition and the bolts are all properly torqued. The metal channel plate gaskets crush down a bit due to their design so several torque passes should be made to assure the bolts are all tight.