Here is the best upgrade you can make to your GM transfer case(model 136, 146, 246, 261, 261HD, 263HD, 263XHD, 261XHD). Prevent the ever increasing problem of pump rub.
What is "pump rub"
The GM transfer cases use a gear pump inside the case that is driven off the mainshaft. The pump forces oil to the planetary as well as the drive sprocket sleeve. Because the pump is driven by the shaft, the housing of the pump must 'float' in the rear housing. There are 5 tabs around the housing that fit into spots in the rear housing to position the pump. Over time, the pump can start to wear on the rear housing. GM installed a spring steel clip in the housing intended to prevent wear but the clip can break and render useless
Being that the pump housing is aluminum and is a harder material then the magnesium rear housing, it can wear a hole in the rear housing and cause a very small leak. This leak is high enough in the case that it typically will not leak when vehicle is not moving and therefor not leaving any drops on the ground. Typically the condition is not found until there is transfer case damage from running the case out of fluid.
Avoid costly repairs to your transfer case by preventing this condition.
Included in the kit:
• Merchant Automotive billet transfer case pump housing
• Transfer case adapter gasket at trans
• RTV Silicone
• Blue Threadlock
• Merchant Automotive sticker
If you already have a hole in your case, its recommended to install a new rear housing for a proper repair. Lifetime warranty will only apply to installations with a new rear housing.
YEAR TRUCK WEIGHT MODEL NUMBER
1998-2007 SILVERADO / SIERRA 1500, 1500HD, 2500, 2500HD, 3500 NP246, NP261HD, NP263HD, NP261XHD, NP263XHD
1998-2003 BLAZER/JIMMY - NP236
1999-2005 ASTRO/SAFARI - NP136
1999-2007 ESCALADE - NP246, NP149
2002-2007 AVALANCHE 1500, 2500 NP246, NP261, NP263, NP263HD
1998-2007 SUBURBAN/YUKON XL TAHOE/YUKON 1500, 2500 NP246