surging in reverse

i have had this problem for a while now...i have a 97 Z71 170,000 miles with a 350 and a 4l60e trans my problem is when my truck is cold and i put it in reverse you have to give it some gas to move it (about 1000 rpm) then it will go without pushing the gas but it surges (kinda like the trans is engaging in reverse then comming out then going back in) i am just wondering what the surging is about...i looked in the rear end when i changed the fluid and the only thing i seen was the cross pin in the carrier had a little wear so i replaced it with a good used one...the trans has seen its better days but i'm easy on it does this sound like a tranny problem ?? could anything in the transfer case cause this ?? it only does it in reverse when its cold and once in a blue moon when warm thanks for any information...

bad stall converter