1) (one) Nice late model NP246 Autotrac has encoder motor, 3 speed sensors and front driveshaft $650. +S&H,
1) (one) Front 9.25" IFS differential 4.10:1 ratio, (late model) w/additional pinion bearing lube feed & heavy case (more webbing) w/ARB air locker "just redone" w/new air engage hub on...
You will notice the NP241 has massive torque capacity.
http://www.genuinegmparts.com/pdf/powertrain/GM%20Parts%20Remanufactured%20Transfer%20Case%20Specification%20Chart.pdf
VSSB PIN IN/OUT 1999 GMC, 6.5TD, K2500, 4WD AUTOTRAC, BURB
Vehicles equipped with AutoTrac NP246 t-case have 3 speed sensors (VSS) one is used for VSSB the other two (front/rear drive-shafts) these 2 speed sensors work in concert with ABS wheel sensors and integrate into AutoTrac controller...