AKA Rattle Cap Vent.
While doing a muffler swap I noticed that the rattle cap vent on my rear axle was diligently doing its job. I know it's normal but I don't want gear oil leaking onto the axle and diff - Ford seems to agree, read on. (Picture attached)
Both Steeda and JLT make a catch can for this, but I knew there was a TSB for the GT's so I dropped by the local Ford dealer this morning. Sure enough the TSB also covers the 2013 V6. Part on order and appointment to be scheduled.
Attached is also a picture of the Ford fix, it is a bulb that replaces the rattle cap. For free I will give it a try, but a catch can like the JLT or one like the Shelby is probably in my future.
Thread about the GT TSB is here: Rear Axle Leak TSB - Ford Mustang Forums