4l60e no 4th gear only

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.

I would say since all other gears work and lockup the issue lies in the 4th servo. Since 2nd works that eleminates the 2-4 band and 3rd works so ur 3-4 clutches are fine. Put the stock 4th servo cover back on and see if ur 4th gear comes back if so the billet 4th servo is stuck in the cover

Thanks I'll do that as soon as I get back from son's soccer game. I intended to do it yesterday but didn't get a chance

The oring on outer plate
(the one at the cover) was cut.
Replaced it and fixed the prob. Thank you so much!

I am having a similar issue with my 1999 K1500. Everything shifts wonderfully until 4th and then nothing. Torque converter locks up as well. Was thinking either 4th gear servo or solenoids, wondering if you found anything out with yours yet? Trans was freshly rebuilt about 150 miles ago as well.