96 2dr Tahoe 4x4 problem. Please Help!!

I have a 96 2dr LS with 155,000 miles. I bought it from a owner that had just had the transmission replaced at 152,000. I didnt know anything about the 4 wheel drive system. To let you know, when im in 2 wheel drive, the led never illuminates for 2 high on the push buttons. I can put it in 4 low and that led stays on, but 4 high has never engaged and has never worked. When i take it out of 4 low, i press 2 wheel and it comes out fine. Sometimes I have to press it several times.(Sometimes 4 high and 4 low leds illuminate together),so i just press again until it comes out. I have replaced the push button module already and that didnt fix the problem. Last summer i had an actuater replaced because 4 low quit working, It was replaced and they didnt look into my existing problem. overall:
when in 2 high led nonfunctional.
4 high never has worked
module sometimes showes 4 low and high leds on at same time

Truck runs fine, but 4 high is no good and im concerned if the transmission replacemnet had something to do with this?! Ive had this truck 2 years with this problem.

On top of that...things like the passenger mirror is broke and the driver seat is not powerful enough to adjust while sitting in it. Ive looked on Ebay for them with no luck, any recomendations for a spot to get the parts?
please help!!!!!!!!!!!!!!!!!!!!!!!

This should be scanned with a scanner capable of accessing transfer case info to start with, lots of guess work will result if an inexperienced person tries to fix this.

sounds like a bad T-case/encoder motor. But like Max said you sould get it scanned

Thanks guys!!