Aluminum adapter housing that bolts a GM 4L60E or 4L65E to an NP246 or NP263 transfer case, replacing a cracked, leaking original with gasket and seal.
Red fluid dripping from the joint between the transmission and transfer case on a 4x4 Silverado, Sierra, Tahoe, Yukon, Suburban, Avalanche, Escalade or Hummer H2 usually gets blamed on a seal. On these 4L60E and 4L65E trucks the aluminum adapter housing in that joint is just as likely to be the leak, either cracked through the casting or missing a bolt boss. This is the Dorman 926-890 replacement for GM 15724744, shipped with the adapter-to-case gasket and the output seal so the whole joint gets new sealing surfaces.
A two-wheel-drive 4L60E ends in a long extension housing. On four-wheel-drive trucks that housing is replaced by a short adapter that bolts to the rear face of the transmission case and gives the NP246 or NP263 transfer case something to bolt to. The output shaft passes through it into the transfer case input, and the seal inside keeps ATF on the transmission side. The transfer case runs its own lubricant; GM's owner manual for these trucks lists a separate AUTO-TRAK II fluid for the automatic transfer case and Dexron for the transmission. The adapter also carries the overhung weight of the transfer case on its bolt flange, so vibration from a worn transfer case mount, a bad U-joint, or a hard hit off road all concentrate in that casting.
Degrease the whole joint, then drive a few miles and look again with a light. Fresh fluid starting at the gasket line points to the gasket or a loose bolt; fluid weeping from the middle of the casting means a crack, and no gasket will fix that. Pull the transfer case fill plug and look at the level and color too. Then do a proper hot check of the transmission: GM specifies reading the dipstick at about 180 to 200 F, inside the hot band, and repeating the check to make sure it is consistent. If the fluid smells burned or the truck is already slipping, read our 4L60E common problems guide before deciding whether this is a leak repair or a rebuild.
The listing covers 1999-2006 Chevrolet Silverado 1500 and GMC Sierra 1500, 1999-2001 Silverado and Sierra 2500, 2001-2003 Sierra 1500 HD, 2007 Silverado and Sierra 1500 Classic, 2000-2007 Tahoe, Yukon, Yukon XL 1500 and Suburban 1500, 2002-2007 Avalanche, 2002-2006 Escalade, Escalade ESV and Escalade EXT, 2003-2014 Express 1500 and Savana 1500, and 2003-2007 Hummer H2, with NP246 or NP263 transfer cases behind a 4L60E or 4L65E. Adapter length is not the same across all of those trucks. Measure your original face to face, compare the casting number, or send us your year and VIN before you order. Everything else for this unit is in our 4L60E parts collection.
Drain the transmission or expect fluid to come out of the back of the case. Remove the rear driveshaft and, if needed, the front, then support the transfer case on a jack and unbolt it from the adapter. With the transfer case clear, remove the adapter bolts and take the adapter off the case. Clean both mating faces down to bare aluminum and check the transmission case face for nicks. Install the new gasket dry, set the adapter, and run the bolts down evenly in a cross pattern to your truck's factory torque. Drive the new output seal in square, lube the lip, and slide the transfer case input through it carefully so the lip does not roll. If the old adapter cracked, find out why: replace a collapsed transfer case mount or a worn U-joint before the new casting takes the same abuse. Refill and hot-check the transmission, and check the transfer case level. If the unit is coming apart anyway, the 4L60E/4L65E overhaul gasket and seal kit covers the rest of the sealing, and a slipping 3-4 pack calls for the Stage 3 rebuild kit with 3-4 PowerPack.
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Doing this repair right usually means replacing these at the same time. Same transmission, ships together.
Yes. The kit includes the aluminum adapter housing, the adapter-to-case gasket and the output seal, so you do not have to reuse the flattened original gasket.
No. Two-wheel-drive 4L60E trucks use a long extension housing with a slip-yoke bushing. This adapter is only for 4x4 and AWD applications with an NP246 or NP263 transfer case.
Only if the casting is sound. Clean it and inspect it closely. A crack through the housing or a broken bolt boss will keep leaking with a new seal, which is why many owners end up replacing the adapter after chasing the leak twice.
Dorman 926-890 replaces GM 15724744. Adapter lengths vary across the listed years, so measure your original face to face and match the casting before ordering.
The transmission takes Dexron VI ATF, checked hot. The transfer case uses its own fluid; for the automatic NP246 GM specified AUTO-TRAK II. Check your owner manual for your exact transfer case and fill both to spec.
