Servicing 4 Wheel Drive

Check both axles for leaks.
Check both drive shafts at trans. For leaking seals.
Inspect for all grease fittings on u joints and suspension and grease.
Remove both pumpkin covers, inspect for any sign of worn parts.
The pumpkin covers will have magnets on them inspect for metal shaving.
You need to replace the cover gaskets and clean the magnets.
Remove the fill plug on the housing with a 3/8 ratchet and fill.
Cadillac used to use 90w differental lube and a suplement.
Call the dealer for proper oil.