I need to replace the hub and throw out bearing on my piggie. It's a 9/73 with a 3 finger clutch, 3 speed trans/transfer case. Basically, I want to just slide the trans/transfer out with a tranny jack, put the stuff on the input shaft then slide everything back in with having to lower the trans/transfer case. My question is: Do I need to drain the oil to do this? I'd be removing the speedo cable, dropping the driveshafts, and disconnecting the reverse light switch. Would any of those (aside from the reverse light switch) cause the oil to drain out?