4l60e tranny help

[Z71 Off Road]

I have an '07 Sierra classic z71. A couple months ago i installed a transgo shift kit. Everything has been fine until yesterday. I drove the truck all day then went to move it at night. It literally won't go anywhere. It seems to be slipping, but I've never had any problems what so ever before. If I bring it up to 3k RPMs or so it will start to creep a little bit. I can see the linkage move fine underneath when it is shifted through the gears. I tried switching it in and out of 4wd and that did nothing. Could the 4WD switch cause this type of problem? Any advice on how to start diagnosing this? Thanks for any help!

[bowtie_guy]

Might sound dumb but hows the trans level??