opening the top is like removing the vent plug to drain it... it removed the vacuum created .One more question on this topic....with cap off I could see gear oil up top...this morning I couldn't...it's coming out from behind the prop...never has had a leak..can't imagine having top cap off would make oil flow out
If it (the lower drive shaft preload pin) is pushing the upper drive shaft (and driven gear) up high enough to open the seal at the bottom, then a leak is the absolute least of his problems!The spring loaded button on the top of the lower vertical shaft pushed the upper gear shaft upward in the driveshaft housing enough that the seal did have enough contact with the seal surface extension on the lower gear. A good chance that either the seal surface is rusted or there is a groove worn where the seal makes contact.
As Chris said pressure test the drive with the oil out.
Do the pressure test and the mystery will be solved.I'm still confused as to why it would randomly have an issue. The top cap was off for a few days kinda deal...there has never been a leak...don't get it...it's not even being used...when it was there was no leak
Test it with VERY low pressure... Too much pressure will force the seal lip to seal up again... I'd use less than 10kpa...Lol ok I will test it