One problem related to transmission pump has been reported for the 1999 Chevrolet Silverado. The most recently reported issues are listed below.
Transmission emits an intermittent howling noise during which time torque transfer from engine to drive train is reduced. Noice may last from 10 minutes to 10 hours. Transmission also occasionaly does not engage when starting from a full stop. Dealer first diagnosed as possible faulty transmission pump but did not repair or replace.