Safety Warning

DIY auto repair can cause serious injury, fire, or vehicle damage. These guides are for informational purposes only. Always follow OEM torque specs, wear PPE, and consult a certified mechanic if you are unsure. You are solely responsible for your safety.

SYS.OK|MANUAL.DB● LIVE

HOMESERVICE MANUALSGMC1999FORWARD CONTROL 5.7 R, AUTOMATICREPAIR AND DIAGNOSISEXTERNAL PAGESDIFFERENT CARSECTION 780 (REAR DRIVE AXLE)REPAIR INSTRUCTIONSLUBRICANT LEVEL INSPECTION - REAR DRIVE AXLEINSPECTION PROCEDURE

1999 GMC Forward Control 5.7 R, Automatic

Inspection Procedure

1999 GMC Forward Control 5.7 R, AutomaticSECTION Inspection Procedure

WARNING: This page is about a different car, the 2004 Chevrolet Corvette. However, it is still accessible from the selected car via links, so may be relevant.

Fig 1: Differential, Fill Plug, Lubricant Tag, & Washer

Courtesy of GENERAL MOTORS CORP.

Raise and support the vehicle. Refer to Lifting and Jacking the Vehicle in General Information.
Clean any dirt from around the differential fill plug.
Remove the fill plug, lubricant tag, and washer from the differential.
Check the differential fluid level. it should be even with the bottom of the fill plug hole to no lower than 6 mm (0.25 in) below the opening.
Add new fluid if necessary.
- Fill with synthetic axle lubricant GM P/N 12378261 (Canadian P/N 10953455).
- If necessary, add enough limited-slip differential lubricant additive GM P/N 1052358 (Canadian P/N 992694), or equivalent to maintain the original ratio of 1.6 L (1.69 qt) of axle lubricant to 118 ml (4.0 oz) of limited-slip additive.

NOTE: Refer to Fastener Notice in Cautions and Notices.

Install the fill plug, lubricant tag, and washer to the differential.
Tighten: Tighten the differential fill plug to 35 N.m (26 lb ft).
Lower the vehicle.

RENDER: 1.0x

NO RELATED

Recommended Tools & Savings

Use the Manual With the Right Hardware

Pair factory procedures with proven DIY tools so the instructions are easier to execute.

Affiliate disclosure: We may earn a commission at no extra cost to you.

Shop Manual-Ready Tools Free Quote Check Quote Shield Pro

When to See a Mechanic

Stop DIY work and contact a certified mechanic immediately if any of the following apply:

• You smell fuel, burning insulation, or see smoke.
• Brakes feel soft, pull hard to one side, or make grinding noises.
• The engine overheats, stalls repeatedly, or misfires under load.
• You are missing required tools, torque specs, or safe lifting equipment.
• You are not confident in the next step or safety outcome.