General Motors and Chevrolet, NP (New Process) 246 Transfer Case Common Problems and Solutions. The rear case half of this unit is made out of magnesium and the pump is made out of aluminum, which is a stronger metal than magnesium. Friction and vibration between pump and rear case half wears tiny pin holes in the rear case slowly causing oil to leak and eventually burning up the GM 246 transfer case. High Gear updates the 246 unit with a metal plate in between the pump and rear case half to reduce friction and vibration. High Gear also uses a brand new aluminum rear case half on all units it repairs.
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