NP246 Transfer Case Pump Rub Upgrade Repair Kit

This is the pump housing upgrade kit for the GM Autotrac and Active Transfer Case family -- models 136, 146, 246, 261, 261HD, 263HD, 261XHD and 263XHD, 1998 through 2007. It replaces the factory oil pump housing with an aluminum alloy unit and ships with the transfer case to transmission adapter gasket, RTV silicone and blue threadlocker. The transfer case pump itself and the case are not included; this is the housing and sealing hardware.

The problem it fixes is pump rub. Inside these cases the oil pump is located off the rear output and is free to move a small amount against the inside of the rear aluminum case half. Over 100,000 miles or so the pump body polishes, then grinds, a groove into the case wall. Eventually it goes through. Fluid dumps out on the highway, the chain and bearings run dry, and the case is scrap -- which is why used 246 cases so often show a weld or a JB Weld patch on the rear half. The upgraded housing carries the pump so it cannot walk into the case wall, and it is the standard preventative fix when one of these units is already apart.

On the bench: pull the transfer case, drain it, and split the case halves. Inspect the rear half at the pump contact area with a straightedge and a light -- if it is already worn thin or holed, the case half needs to be replaced before you go further, because this kit stops new wear, it does not fill an existing hole. Remove the factory pump housing, transfer the pump over to the new housing, and reassemble. Clean both sealing faces down to bare metal, lay a continuous bead of the supplied RTV, and torque the case bolts in a crossing pattern. Blue threadlocker goes on the housing bolts. Use the supplied adapter gasket where the case meets the transmission.

Refill with the fluid the case calls for -- GM Auto-Trak II (blue) on the 246, 261 and 263 units -- and check the level at the fill plug with the truck level. This is a job worth doing any time one of these cases is open for a chain, a pump, or an encoder motor, since the case is already apart and the failure it prevents takes the whole transfer case with it.