Stops pump rub on GM NP246, 261 and 263 transfer cases by carrying the oil pump in an alloy housing so it cannot grind through the case half.
If your 1998-2007 Silverado, Sierra, Tahoe, Suburban, Yukon, Escalade or Avalanche has a transfer case that keeps going low on fluid with no puddle in the driveway, or a wet, grimy spot on the back of the case, pump rub is the first thing to rule out. This kit replaces the factory oil pump body in GM NP136, 146, 246, 261, 261HD, 263HD, 261XHD and 263XHD transfer cases with a machined aluminum housing designed so the pump cannot wear through the case.
These cases have no oil bath for the planetary and drive sprocket; an internal pump driven by the mainshaft picks fluid up and feeds those parts. Because it is shaft-driven, the pump body floats inside the rear case half, located by tabs and held still by a spring-steel anti-rattle clip. The case halves are magnesium and the pump is aluminum. Once the clip wears or breaks, the pump tabs ride directly on the softer magnesium and slowly cut a pin hole through the rear half. The upgrade housing in this kit uses larger indexing tabs so the load is spread over more of the case surface. The factory anti-rattle clip is discarded; it is not used with this housing.
Fill the case to the level plug and watch it over a week of driving; pump-rub leaks show up while moving, not parked. Clean the rear half and look for fresh fluid at the pump castings. If you are tracing a noise, rule out the transmission first with our 4L60E whine vs clunk guide, since the two share a tailhousing joint. Once the case is split, inspect the rear half at the pump contact area with a light. This kit stops new wear; it does not repair a hole. If the case is already holed or worn thin, replace it with the NP246 rear half housing; on a heavy-duty NP261 or NP263, use the matching rear half for that case.
Fits GM transfer case models 136, 146, 246, 261, 261HD, 263HD, 261XHD and 263XHD used from 1998 through 2007. That covers the Autotrac NP246 in half-ton trucks and SUVs as well as the NP261 and NP263 cases in 2500 and 3500 trucks. Read the model tag on the case before ordering, or send us your year and VIN. One caution from the design side: upgraded housings like this may not suit some aftermarket aluminum rear case halves because of inconsistent tolerances, so test-fit before final assembly if your case has been replaced. The truck's transmission and adapter parts are on our 4L60E and 4L80E pages.
| Fits transfer case models | |
| Years | |
| Housing material | |
| Kit contents | |
| Reference number | |
| Not included |
No. It is the pump housing (body) plus the adapter gasket, RTV and threadlocker. You reuse your original pump gears and cover inside the new housing.
No. The housing stops new wear but cannot seal an existing hole. Replace the rear case half, then install this housing so the new half does not wear through too.
GM 1998-2007 four-wheel-drive Silverado and Sierra pickups, Tahoe, Suburban, Yukon, Yukon XL, Escalade, Avalanche and related models with the 136, 146, 246, 261 or 263 family cases. Check the tag on the case to confirm.
Pump-rub leaks typically drip while the truck is moving and stop when it is parked, so the fluid ends up on the chassis and the road instead of the driveway.
GM Auto-Trak II on the NP246, NP261 and NP263. Fill to the fill plug with the truck sitting level.
No. Remove and discard the factory clip and any broken pieces; it is not used with the upgraded housing.
