1996 GMC Sonoma Owner's Manual - Page 324

Long Trip/Highway Maintenance Schedule ** Drive axle service: 0 The services shown in this schedule up to 100,000 miles (166 000 km) should be performed after 100,000 miles (166 000 km) at the same intervals. Footnotes The U S . Environmental Protection Agency or the California Air Resources Board has determined that the failure to perform this maintenance item will not nullify the emission warranty or limit recall liability prior to the completion of the vehicle's useful life. We, however, urge that all recommended maintenance services be performed at the indicated intervals and the maintenance be recorded. 0 Locking Differential -- Drain fluid and refill at first engine oil change. At subsequent oil changes, check fluid level and add fluid as needed. If driving in dusty areas ortowing a trailer, drain fluid and refill every 15,000 miles (25 000 km). Standard Differential -- Check fluid level and add fluid as needed at every engine oil change. If driving in dusty areas or towing a trailer, drain fluid and refill every 15,000 miles (25 000 km). More frequent lubrication may be required for heavy-duty or off-road use. 0 7-32