I just got an 03 ZD21 with a little over 2,000 hrs. It ran low on hydraulic oil and would barely move on me. I checked the fluid level and it was low, so I added some fluid and it started going again. Once I got it inside and parked I noticed that the bottom of the trans was wet. At first it looked like it was coming from the drain plug, but that was tight and not leaking. It looks like right behind the drain plug, there is something held in with a snap ring and that's where its leaking from. What exactly snap ring holding in? Is this common? Thanks