I have a Allison MD3060 that had (i just checked and no more drips!) an oil leak, not much but enough to leave a pie plate stain on the pavement after being parked for a few days.
In looking at the possible cause of the leak I thought it was a loose pan bolts/gasket. I went around the pan and torqued all the pan bolts to 40 ft/lb. Be careful what are pan pan bolts and want aren't, as in the middle of the pan there is a series of pressure taps for the clutch packs. Some bolts I was able to get a full turn on.
In looking closer I believe I discovered the true nature which is either the wiring harness coming out above the oil pan or it's the optional oil fill/dip stick position. In talking with my local Allison distributor they said there is a expandable plug in the housing for the dipstick and to try and see if it's tight. I was able to get two or three turns on the bolt that is visible. Use a 13mm and a pair of Channelocks or Kimpex pliers grab the flat washer below the bolt to keep it from turning. He said if it it doesn't quit leaking to pull it out clean it with BrakeKleen and put a light film of RTV sealant on it. What was also interesting was he said the oil level is probably above the this plug level with the engine shut off. He went on to say that if I needed to pull the plug was to put in neutral, block the tires, put the brake on and pull the plug with the engine running as the oil level will have gone down enough to remove the plug without loosing any oil. I'm more than a little leary of doing this.......
Hope this helps anyone out there with an Allison leak.
