GMC 2001 C3 Owner's Manual page 365

Weatherstrip Lubrication
Silicone grease on weatherstrips will make them last
longer, seal better, and not stick or squeak. Apply
silicone grease with a clean cloth. During very cold,
damp weather more frequent application may be
required. See "Recommended Fluids and Lubricants"
in the Index.
Automatic Transmission Check
Check the transmission fluid level; add if needed. See
"Automatic Transmission Fluid" in the Index. A fluid
loss may indicate a problem. Check the system and
repair if needed.
7-18
At Least Once a Year
Key Lock Cylinders Service
Lubricate the key lock cylinders with the lubricant
specified in Part D.
Body Lubrication Service
Lubricate all body door hinges, hood latch assembly,
secondary latch, pivots, spring anchor, release pawl,
tailgate hinge, tailgate linkage, tailgate handle pivot
points, latch bolt, fuel door hinge, locks and folding
seat hardware. Part D tells you what to use. More
frequent lubrication may be required when exposed
to a corrosive environment.