4l60e no 4th gear only

[mrfister]

I searched but didn't really find anything. So here goes...

I'm having a prob. w/ my 2002 Silverado 2wd 4l60e. Rev. 1st 2nd 3rd and the TCC locks up (I set it to lock up in 3rd to check). Used HP Tuner to command 4th, nothing. No MIL, trans has all available upgrades minus the Sonnax Smart Tech Input Drum. 3-4 and intermediate servo is Superior/Fairbanks Max. Overdrive.
The torque converter is a Yank 3600 SST. Has the Trans-Go shift kit and VB plate.
Trans is very strong, you would never know it has prob. 'till it doesn't shift into 4th. It also won't do it by using the shifter manually. Also I can hear the solenoids when I manually turn them on & off w/
Hp Tuners.