Purchased from a site sponsor and currently in a 2002 yukon that is stock besides of a yank converter and wheatly tune. been loving it since the install (maybe a year) but the other week i drove it and noticed a hard 3-4, overdrive, whatever shift. part throttle and going around 50 it thumps hard. just wondering what might be causing this and if its something i'm capable of fixing. all other shifts and fluid looks good. thanks.

looking around on the net a little...possible od servo issues?

 

Is it only the 3-4 shift doing it?
Do you have any codes?

 

no codes on the dash and yes, its only the 3-4 shift. its the wifes and i rarely drive it. she didn't even notice it until i mentioned it to her. i somewhat remember a month or so ago i thought the shift was a little firm but its a down right thump now. seems to be something that gradually worsened.