BK351-style bearing, seal and gasket kit for the NP246 AutoTrac transfer case in 1998-2006 Silverado, Sierra, Tahoe, Yukon, Suburban and Escalade.
If your 1998-2006 Silverado, Sierra, Tahoe, Yukon, Suburban, Escalade or 2002-2006 Avalanche has a transfer case that growls in Auto 4WD, weeps at the front or rear output, or is coming apart anyway for a chain or pump repair, this is the bearing, seal and gasket set for the New Process NP246 AutoTrac case. It follows the BK351 parts list, so every bearing and seal the case uses is in the box and the unit goes back together without a second teardown.
The NP246 is GM's "active" transfer case. In 2WD all torque goes straight out the rear output. In Auto 4WD the transfer case module shifts into 4 High with the encoder motor and then applies an internal clutch pack, using a pulse-width-modulated current, to send torque through the chain to the front output whenever it sees the front and rear propshafts turning at different speeds. In 4 High the clutch is fully applied for a 50/50 split, and 4 Low adds a planetary reduction of about 2 to 1.
All of that rides on the parts in this kit. The input bearing and mainshaft pilot bearing carry the input and mainshaft, the front output bearings carry the lower sprocket the chain drives, and the clutch apply plate bearing takes the thrust when the encoder clamps the clutch pack. The three lip seals keep the small fluid volume in, and since that fluid also tunes how the clutch pack engages, a slow leak changes how the case behaves long before it runs dry.
Pull the fill plug first. Low fluid, metallic paste on the drain plug magnet or a gray, glittery fluid tells you the case is wearing internally. Then rule out what sounds like the case but is not: tires, wheel bearings, the front differential and the transmission. Our 4L60E whine and clunk guide walks through separating transmission noise from driveline noise. If you are chasing an Auto 4WD complaint or chassis codes rather than noise, measure the tire circumference on all four corners and equalize pressures first, because the module reacts to tiny speed differences between the propshafts and mismatched tires will make a healthy case misbehave.
This kit fits the NP246 used in 1998-2006 Chevy Silverado and GMC Sierra pickups, the Tahoe, Yukon, Suburban and Cadillac Escalade, and the 2002-2006 Avalanche with the 5.3L or 8.1L. These trucks ran the NP246 behind both the 4L60E and the 4L80E. Read the ID tag on the rear case half before ordering and confirm it says 246. The NP236 and NP261/NP263 look very similar from under the truck but use different internals. If the tag is missing or the case has been swapped, send us the year and VIN and we will confirm it.
The drive chain, oil pump and clutch pack are not included. Inspect them while the case is open and replace them if they are worn.
| Transfer case | New Process NP246 (AutoTrac) |
| Fits | 1998-2006 Chevy Silverado, GMC Sierra, Tahoe, Yukon, Suburban, Cadillac Escalade; 2002-2006 Avalanche 5.3L and 8.1L |
| Replaces | BK351 bearing and seal kit |
| Includes | Input shaft bearing, front output shaft front and rear bearings, mainshaft pilot bearing, output shaft bearings, clutch apply plate bearing, shift detent lever bearing, front input, front output and rear output seals, input shaft thrust washers, access hole plug, shift fork pads, retainer rings, O-rings, case gasket |
| Not included | Drive chain, oil pump, clutch pack |
| Weight | 4.3 lb |
If the case is the NP246, yes. Auto 4WD on a 1998-2006 GM full-size truck almost always means an NP246, but read the tag on the rear case half to be sure. A tag ending in 236 or 261/263 means a different case.
Use GM's AutoTrac transfer case fluid, Auto-Trak II on most years. The friction modifiers in it control how the clutch pack engages in Auto 4WD. Do not use regular ATF or gear oil, which can cause chatter and early clutch wear.
No. It covers bearings, seals, thrust washers, fork pads, snap rings, O-rings and the case gasket. Check the chain and pump while the case is open, and add the HV-072 chain or pump rub kit if needed.
The front and rear output seals can be changed on the truck once the driveshafts and yokes are off. If the leak came with bearing noise, though, the bearings are worn and the case needs to come apart.
Usually not. A flashing light or chassis codes more often point to the encoder motor, the speed sensors, or mismatched tire sizes. Check tire circumference and the encoder before rebuilding the case for an electrical symptom.
