4l80e shutter problem

I have 97 2500 4x4 burb with 5.7l , I just started having a problem with torque converter lockup ,above 42 mph when converter locks up it shutters ,i thought it was a miss at first (couln't fig out)so i took it to local shop ,they changed fluid & added additive to it told me it was the converter & try do drive it for a while and if the additive doesn't work they would change the conv.well it's still shutering i'm thinking i can change the converter myself,should I or take it to trans shop could it be the tcc valve ?? any suggestions

It could be the tcc apply valve. See http://www.transmissionspecialty.com/parts/parts/34994-01K.htm

I think you need to drop the valve body to replace it. Might be time for a Transgo Reprogramming kit (since you have to take the valve body out anyways :biggrin: )

//2000CAYukon