The steering gear is factory-filled with a lubricant which does not require seasonal change. The housing should not be drained; no lubrication is required for the life of the gear.
Use GM steering gear lubricant No. 1052182 or equivalent.
The steering lubricant should be checked every 6 months or 7500 miles. The gear should be inspected for seal leakage when checking the lubricant. Look for solid grease, not an oily film. If a seal is replaced or the gear overhauled, it should be refilled with lubricant.