1999 GMC Sierra 1500 Pickup Owner's Manual - Page 317

Hydraulic Clutch Grease Fitting A grease fitting is ontheclutchhousingforlubricatingtheclutchforkball stud.SeeyourMaintenanceScheduleforwhentolubricatethe clutch housing.See"RecommendedFluidsandLubricants" in theIndexforthe proper lubricant to use. Be sure not to over-fill becauseyoucoulddamageyour clutch. Four- Wheel Drive Mostlubricantchecks in thissectionalsoapply to four-wheel-drivevehicles. However,theyhave twoadditionalsystemsthatneedlubrication. Transfer Case When to Check Lubricant: Refer to theMaintenanceSchedule to determinehowoften to checkthe lubricant.See"PeriodicMaintenanceInspections" in theIndex. How to Check and Add Lubricant: I PO230 If the level is belowthebottom of thefiller plug hole,you'llneed to add somelubricant.Addenoughlubricanttoraisethelevel to thebottom of the fillerplughole. What to Use: Refer to theMaintenanceScheduletodeterminewhat kind of lubricant to use. See"RecommendedFluidsandLubricants" in the Index. 639