Rough tranny

Hi, I have a '78 Jeep CJ 5 with a 258 straight six motor. Lately I have been having a problem with 2nd and 3rd gear. When the gears wind up, the Jeep seems to feel like it is rumbling hard until I back off. Also I hear a sound like "tch tch" from under the drivers side hood:banghead: . I was worried about the fluid levels in the tranny so I checked the level on the case and found oil on my finger so I think that is o.k:cool: . The motor oil is about one quart low but the engine is smooth. The clutch moves between the gears as usual since I had the clutch replaced about three years ago. Do you have any idea what might be going on?
:confused:

"Tch tch" might be an exhaust leak. Rumbling I would guess your Ujoints. Anything more specific? Is the rumble speed specific? That is, does it increase as you go faster and decrease as you slow?