2001 Rubicon trans query?????????

Howdy. I spent hours scouring former posts but couldn't find any doing what this rubicon i picked up is doing.......

D1,D2,reverse,ESP1 all: when torque is applied i get a klunk-klunk-klunk-klunk that varies with the engine speed. it almost sounds aboult half speed the crank is turning.

the trans has clean,correct oil,no bad codes.

weird thing is,if i run in low range and esp,and start out in 5th,it won't skip or make the noise-you can hammer it hard-same in hi range esp once you get into 5th.

idling in 1st gear and apply throttle slowly and it wants to go until it slips. you can slow the slip down to a steady rythem and the bike just sits there and hop,hop,hop-trying to go and slip at perfectly timed rythem.

i guess the tranny is probably shot,but i found it odd that it shifts thru all the gears pefectly. all shifts and the esp are lightning quick.

it acts like something that controls the tranny-clutch maybe?

reverse does it the same but the noise is a little less deep in tone.

i guess i should note that if you really hammer the throttle in the lower gears it makes the noise but it will move.

any help is appreciated!