It is stuck on first or second gear. Rear is ok, but no shifting 1>2>3>4. Able to start from "Winter drive" from 3rd. When I drive it shifting to 3rd gear possible only when I press "Winter Drive" with some shock. When I depress "Winter Drive" it is back to 1st or 2nd (I'm not sure which one) also with shock.
No "Engine Check" or "Transmission Check" lights.
Shift position indicator is ok.
All fuses and all connectors are checked.
Please, help with ideas.
Thank you.

2001 Trooper LS 3" lift,no more Rancho 9000RX,
no more 4L30E transmission,
ProComp 8" 130W driving lights,
Surco roof rack (modified),
110V power outlet, Viair 380C compressor,
CB/FRS/GPRS/HF/VHF/UHF Radio, 285/75/16 BFG AT/KO.