Yukon Gear Dura Grip Positraction For GM 8.5in w/ 28 Spline Axles

Yukon Gear DuraGrip Positraction for GM 8.5 Inch with 28 Spline Axles

The GM 8.5 inch 10-bolt rear axle is one of the longest-running rear differentials in General Motors history, used in everything from 1970s muscle cars and trucks to 1990s Blazers and C/K pickups. The YDGGM8.5-3-28-1 Yukon Gear DuraGrip provides a clutch-style limited slip upgrade for any GM 8.5 inch 10-bolt equipped with 28-spline axle shafts and a gear ratio of 2.73 or numerically higher. Part number YDGGM8.5-3-28-1 features forged 4320 chromoly spider gears, a nodular iron carrier case, and composite clutch packs that deliver consistent traction transfer without the noise or harshness of cheaper limited slip designs. The YDGGM8.5-3-28-1 is a direct replacement for worn factory positraction units or open differentials in this extremely common GM rear axle platform.

Features and Benefits

• Fits GM 8.5 inch 10-bolt rear differential with 28-spline axle shafts
• Compatible with 2.73 and numerically higher gear ratios
• 4-spring, clutch-style positraction for smooth torque transfer
• Forged 4320 chromoly steel spider gears for maximum strength
• Nodular iron carrier case for structural durability
• Composite clutch packs minimize chatter under normal driving
• Fully rebuildable design with available clutch pack kits
• Assembled in the United States
• Note: requires carrier bearings LM102949 and LM102911
• One-year manufacturer warranty

Vehicle Fitment

Specifications

What Is Included

• One fully assembled DuraGrip positraction differential carrier
• Composite clutch packs and 4-spring preload assembly pre-installed
• Forged 4320 chromoly spider gears installed

Frequently Asked Questions

What is the difference between the GM 8.5 and GM 8.6 inch differential?
The GM 8.5 inch was used from the early 1970s through approximately 1998. The GM 8.6 inch is a revised version used from approximately 1999 onward in the new-body trucks and SUVs. The YDGGM8.5-3-28-1 covers the 8.5 inch application with 28-spline shafts. For the 8.5 or 8.6 with 30-spline shafts, see YDGGM8.5-3-30-1.

Does YDGGM8.5-3-28-1 require any additional bearings?
Yes. This unit requires carrier bearing part numbers LM102949 and LM102911, which must be purchased separately. Always replace carrier bearings when installing a new differential carrier.

Will this positraction make my truck spin both rear tires?
The YDGGM8.5-3-28-1 is a limited slip, not a locker. It transfers torque to the wheel with better traction while allowing some differentiation during cornering. Under hard acceleration from a standstill, both tires will engage with some bias.

Is YDGGM8.5-3-28-1 compatible with the factory ring gear?
Yes. The carrier uses the factory 10-bolt ring gear bolt pattern. Reuse your existing ring gear or install a new gear set at the same time as the differential upgrade.

What gear oil is required?
Use high-grade non-synthetic GL-5 gear oil with Yukon LSD additive (part number OILADD). Yukon Gear does not recommend synthetic oil for this unit, as it may cause clutch noise.

Does the Magnuson-Moss Warranty Act apply to my truck?
Under the Magnuson-Moss Warranty Act, installing YDGGM8.5-3-28-1 cannot automatically void your vehicle warranty. A dealer must specifically demonstrate that this part caused a covered component failure to deny a warranty claim.

Can I rebuild the YDGGM8.5-3-28-1 clutch packs?
Yes. Rebuild kits are available for the DuraGrip platform. The fully rebuildable design means you do not need to purchase a new unit when clutch material eventually wears.

Does the 8.5 GM axle support the power levels of a modified engine?
The GM 8.5 inch is generally considered adequate for mild to moderate street performance. For high-horsepower dedicated performance builds, upgrading to a larger axle such as a GM 12-bolt or 14-bolt is recommended.

Installation Instructions

1. Raise and support the vehicle. Drain differential fluid and remove cover, driveshaft, and axle shafts.
2. Mark differential bearing caps for position before removal.
3. Remove caps and extract the old carrier with shims. Keep shims separated by side.
4. Press new carrier bearings (LM102949/LM102911) onto the YDGGM8.5-3-28-1 carrier.
5. Transfer the ring gear from the old carrier using fresh ring gear bolts torqued to specification.
6. Reinstall with original shims. Measure backlash with a dial indicator (target 0.005 to 0.009 inch for GM 8.5).
7. Verify carrier preload and contact pattern with gear marking compound.
8. Torque bearing caps to spec. Reinstall cover with RTV or new gasket.
9. Fill with GL-5 gear oil and Yukon LSD additive. Reinstall driveshaft and axle shafts.
10. Road test and recheck for leaks and noise after 100 miles of break-in driving.

Proposition 65 Warning: This product can expose you to chemicals including arsenic, which is known to the State of California to cause cancer. For more information, go to www.P65Warnings.ca.gov.