Rumbling Explorer

I've got me a 1995 Explorer with a developing "rumble". This occurs over 40 mph. Have replaced both driveshaft u-joint, ball joints, left front axle shaft, transmission mount, brakes all within the last year. There is no play in the u-joints. I dont feel the rumble in the front end...its the whole truck. There is also a "clunk" when the trans downshifts. Could this be my slipyoke in my driveline or maybe my trans output shaft brg? The downshift clunk happens at any speed..not a major clunk but an irritating clunk that feels like it shouldnt be there. I bought the truck used 2 years ago and clunk has always been there. Its the rumble all of a sudden that bothers me.......Please help with any ideas....Thanx

I had a rumble and thought it was front wheel bearings becuase I could feel it in the steering wheel. Turned out to be bad tire wear on the inside of the driver's front tire.