NP246 Transfer Case Drive Chain HV-072 1.25 in Wide

This is the drive chain that carries torque from the mainshaft sprocket to the front output shaft sprocket inside GM chain-drive transfer cases. It is OE part number HV-072: 1.25 in wide, .375 in pitch, 49 links. It fits the NP149, NP241, NP243, NP246, NP261 and NP263 cases used behind GM automatics in Silverado, Sierra, Tahoe, Yukon, Suburban, Avalanche and Escalade with the 5.3L, 5.7L and 6.0L V8.

Chains stretch. That is the normal wear-out mode on these cases, and it shows up as driveline slop and a clunk when you get on and off the throttle, a whine or growl that tracks vehicle speed in AWD or 4HI, and glitter in the fluid when you pull the drain plug. On the Autotrac units (NP246, NP149) a badly stretched chain starts slapping the inside of the aluminum case and wears a groove in the housing. Once that groove is cut you are buying a case half instead of a chain, so this is a part worth changing early rather than late.

On the bench: drain it, pull the rear output housing, break the case halves apart, and lift the mainshaft, front output shaft and chain out as an assembly. Compare the old chain to the new one laid flat - a stretched chain is visibly longer and will show side-to-side slop you can feel. Loop the new chain over both sprockets before you set the shafts back into the front case half, then reseal the case halves with anaerobic sealant and torque the bolts in a cross pattern. While the case is open, check the sprocket teeth for hooking and the oil pump pickup for debris - a chain that stretched far enough to make noise usually left metal behind. Refill with the fluid the case calls for: Auto-Trak II for NP246 and NP149, ATF for the NP241 and NP243 units.