The GM 10-bolt differential was featured in both truck and passenger vehicle applications. Chevrolet 1/2 ton, 3/4 ton and 1977 through 1991 Blazer sport utility vehicles utilized the GM 10-bolt differential in front axle four-wheel drive applications. Certain GM 10-bolt rear end differentials utilize limited slip technology, also known as "Positraction." Because of the wide range of applications for the 10-bolt GM differential, several final drive gearing ratios are available. Checking to see if your Chevrolet vehicle has a 10-bolt differential will allow you to better prepare when repairing or performing maintenance to your front or rear drive axles.
Place your vehicle in "Park" and engage the parking brake. (ref#2)
Examine the rear axle carrier, underneath your vehicle. The rear axle carrier features a round cover, located between the left and right axle tubes, visible from the rear of the vehicle.
Count the number of bolts that secure the differential cover. As the name implies, GM 10-bolt differentials will utilize 10 bolts to secure the differential cover to the carrier. Differentials that feature Positraction will have a small identification number comprising two or three digits, located on the lower right side of the differential cover.
Repeat the above steps when identifying front differential types in four-wheel drive applications.
