I have a 99 yukon, transfer case will not shift.

I also replaced the device on the front axle to kick it in, and at the same time the tranny started shifting eratically,

Ihave an 04 yukon xl 1500 my shift motor went out about a year ago. I pulled its fuse and removed it and used a wrench to manualy shift it back into 2wheel drive and only issue i have had in almost a year of driving like that was when i was towing a trailer that was alittle over my tow capacity and the comp. Auto shifted it into 4low*. BUT no shifter motor....so computer is thinking the car is in 4low but physicaly its still in 2wheel drive and it doesnt want to come back out of 4low easily. I wondered if i applyed same methid of clearing a computers (desktop) memory (turn off, unplug, remove cmos battery, hold power till all residual power is out of line nd all lights shut off) which clears all the error codes and bad codes from the memory of the comouter) wouod work on my csrs computer so i turned my truck all the way off and disconected the battery and let it set for about 30 min. To let the comp. clear its self and reset itself.Hoping tht it woukd restatt back in 2wheel drive and it worked. And i hardly ever actully need 4wd so i just left that shifter motor off and manualy shift it if i ever really need to go into 4wd. Hope this helps someone on here.