Rebuilds the GM NP246 electronic-shift transfer case with all new bearings, input and output seals, adapter gasket, and O-rings to stop pump-rub leaks.
When the transfer case under a 1998-2007 Chevy Silverado 1500, Tahoe, Suburban or Avalanche, a GMC Sierra, Yukon or Yukon XL, or a Cadillac Escalade starts howling at highway speed, drips at the output yokes, or has already been split open for a pump-rub repair, this BK-351 kit is the bearing and seal set that lets the New Process NP246 go back together right. It carries every internal bearing in the case, the front input seal, the rear output seal, the case-to-transmission adapter gasket and a full set of O-rings, so you are not reusing a single worn rolling part once the case halves are apart.
The NP246 is GM's AutoTrac case: a two-speed chain-drive unit with a 2HI, AUTO, 4HI and 4LO button on the dash. In 2HI it sends everything straight out the rear output. In AUTO the module shifts the case into high-range 4WD with the encoder motor and then varies the clamp on an internal clutch pack to feed torque through the chain to the front driveshaft only when the front and rear propshafts stop turning at the same speed. 4HI clamps that clutch fully for a 50/50 split, and 4LO adds a planetary reduction of roughly 2 to 1.
Every one of those modes spins on the bearings in this box. The input bearing carries the shaft coming off the 4L60E or 4L80E, the mainshaft and output bearings keep the rear output and drive sprocket on center, and the front output bearings support the lower sprocket the chain wraps around. If any of them develops play, the chain runs out of line, the clutch pack loads unevenly and the noise climbs from a hum to a growl. The seals and O-rings keep the small fluid fill inside the case, and on an NP246 the fluid is also what the internal pump feeds to the clutch pack, so a slow leak is never just a drip problem.
Rule out the transmission and axles first. A tired 4L60E planetary or a bad pinion bearing can sound a lot like a transfer case, and our 4L60E whine vs clunk noise guide walks through separating them by gear and load. Next, check the transfer case fluid level and look at what drains out; glitter is wear, chunks mean the case is coming apart. Then measure all four tires around the tread. A Transmission Digest technical article on this case notes the module reacts to as little as a 15 rpm difference between propshafts, so mismatched tires can make an otherwise healthy case bind and set codes. If the rear half is weeping, read our NP246 pump rub fix and cost guide before you pull it, since the case half may need attention too.
This kit is listed for the GM NP246 (also stamped NV246) electronic-shift case in 1998-2007 GM full-size trucks and SUVs: Silverado 1500, Sierra 1500, Tahoe, Suburban, Yukon, Yukon XL, Avalanche and Escalade. It bolts behind both the 4L60E and the 4L80E. The 2007 model year is the one to watch: GM changed AutoTrac cases during the redesign, so a 2007-2009 truck can carry either an NP246 or a later MP3023, and the parts do not interchange. Read the ID tag on the rear case half before ordering, and our NP246 vs MP3023 comparison shows how to tell them apart. If the tag is missing, send us the year and VIN and we will check it.
The kit weighs just under 4 lb, uses high-strength steel bearings, and ships fast from the USA.
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It fits the 2007 trucks that still have the NP246. GM switched AutoTrac cases during the 2007 redesign, so some 2007-2009 trucks use an MP3023 instead. Read the tag on the rear case half, or send us the year and VIN to confirm.
No. BK-351 is bearings, input and output seals, the adapter gasket and O-rings. If the pump has worn into the rear case half, add the pump rub upgrade kit or a replacement rear half.
Only if the leak is at a seal or the adapter gasket. Pump rub wears through the case wall, so the pump needs a new housing or saver and the rear half may need replacing once it has holes in it.
Yes. The NP246 was used behind both automatics in GM half-ton trucks and SUVs, and the internal bearings and seals in this kit are the same for either.
Use the AutoTrak II-type transfer case fluid GM lists for your truck in the owner's manual. Do not substitute ATF or gear oil, because the fluid controls how the AUTO clutch pack engages.
