I have a '99 Tahoe that won't move, it's almost like the transfer case is locked up. I pulled the driveshafts, everything turns. I pulled the encoder motor off, I was able to shift the case manually with no problems, and front axle is free in 2HI. I put another encoder motor on that i had laying around, and with the ignition on and engine off, everything seemed to be ok. However, once I started the engine I was right back to things acting like they're locked up. TCCM bad? First time with one of these.