I noticed a decent amount of oily accumulation on the bottom of my Diesel (about 70,000 miles) last oil change, but didn't have time to investigate further. I also don't have anything hitting the ground. The accumulation is near where the engine and transmission join up, and everything around the perimeter of the the oil pan feels dry. So, I'm guessing either rear main or transmission is leaking, since the accumulation is on the opposite end of the engine from the oil filter. I'm also getting some rough downshifts like before I switched to the AMSOil fluid, which makes me wonder if transmission is low. Once I get my Jeep back together and out of the garage (in the middle of a month-long brake, suspension, and front end overhaul on it, along with draining and replacing every fluid in it front to rear), I need to pull the Diesel in and check the trans level, pull the aero panel, and investigate the leak. I figure I've got another 30k and 18 months of powertrain warranty left, so I don't have to be in a hurry to get to it.