One problem related to crankcase (pcv) has been reported for the 1997 GMC Sierra. The most recently reported issues are listed below.
Vehicle stalled while driving. Had coasted to side of road. Restarted & vehicle shut off. The differential seal was leaking oil. The vehicle was making noises in the universal joint. Taking vehicle to mechanic. Also, leaf spring on passenger's sid efailed/replaced/smelled oil due to pcv valve failure, an dtransmission would not shift into drive or reverse.