Yukon Gear High Performance Gear Set For GM 8.5in & 8.6in in a 4.88 Ratio

Yukon Gear Ring and Pinion Set for GM 8.5 and 8.6-Inch 10-Bolt Differential in 4.88 Ratio

The YG GM8.5-488 from Yukon Gear and Axle is a high-performance 4.88 ratio ring and pinion gear set for the GM 8.5-inch and 8.6-inch 10-bolt rear differential. The GM 8.5 and 8.6 are the most common rear axles on Chevrolet and GMC light-duty trucks, SUVs, and vans from 1980 through 2017, making the YG GM8.5-488 one of the most widely applicable regear options in Yukon's catalog. A 4.88 ratio provides substantial low-end torque multiplication for lifted trucks running 35-to-37-inch tires who need aggressive off-road performance and towing capability. Yukon machines the YG GM8.5-488 from premium alloy steel with advanced tooth geometry validated through two dedicated in-house quality labs. Whether you are building a Silverado, Tahoe, Yukon, Suburban, or Avalanche for trail use or heavy-duty towing, the YG GM8.5-488 is a proven direct-fit solution backed by Yukon's Y.E.S. lifetime warranty plan.

Key Features and Benefits

• 4.88 Gear Ratio: Aggressive torque multiplication for builds running 35-to-37-inch tires, correcting for significant lift and tire oversize
• GM 8.5 and 8.6 Fitment: Fits both 8.5-inch and 8.6-inch 10-bolt carriers covering 1980 through 2017 applications
• 30-Spline Pinion: Matches the heavy-duty 30-spline GM 10-bolt carrier configuration
• Premium Alloy Steel: High-strength material precision machined and heat-treated for long service life
• Advanced Tooth Geometry: Optimized tooth profile minimizes friction and heat buildup under sustained load
• Dual Lab Verification: Every set tested in Yukon's in-house quality labs for dimensional accuracy and load capacity
• Y.E.S. Plan Eligible: Optional lifetime no-questions-asked warranty upgrade available

Fitment

Specs

What Is Included

• Ring gear
• Pinion gear
• Pinion nut

Frequently Asked Questions

• Q: What vehicles does the YG GM8.5-488 fit?
  A: The YG GM8.5-488 fits GM 8.5-inch and 8.6-inch 10-bolt rear differentials in Chevrolet and GMC light-duty trucks, SUVs, and vans from 1980 through 2017, including Silverado 1500, Tahoe, Suburban, Avalanche, GMC Sierra 1500, Yukon, and Cadillac Escalade.
• Q: What tire size is the 4.88 ratio best suited for?
  A: The YG GM8.5-488 is ideal for lifted builds running 35-to-37-inch tires, where a numerically high gear ratio is needed to restore throttle response and towing capacity lost from the tire oversize.
• Q: Does the 4.88 ratio require a carrier change on the GM 8.5?
  A: Yes. The GM 8.5 uses a two-pinion open carrier with separate carrier cases for numerically low and high ratios. A carrier that accepts the 4.88 ratio is required if your existing carrier is sized for lower ratios. Verify before ordering.
• Q: Will I need to replace the carrier bearings?
  A: Yukon recommends using a fresh master install kit with new carrier bearings, pinion bearings, shims, and seals whenever installing the YG GM8.5-488 for correct preload and long service life.
• Q: Can the dealer void my factory warranty for installing the YG GM8.5-488?
  A: The Magnuson-Moss Warranty Act requires the dealer to prove the YG GM8.5-488 directly caused any failure. Simply installing an aftermarket gear set does not automatically void your vehicle warranty.
• Q: Does this gear set fit both the 8.5 and 8.6-inch axles?
  A: Yes. The YG GM8.5-488 is designed to fit both the GM 8.5-inch and 8.6-inch 10-bolt carriers which share the same gear dimensions.
• Q: What warranty comes with the YG GM8.5-488?
  A: Yukon covers the YG GM8.5-488 for one year against manufacturing defects. The Y.E.S. plan provides lifetime no-questions-asked coverage.
• Q: Is professional installation required?
  A: Yes. Gear installation on the GM 8.5 requires precise pinion depth, backlash, and preload settings achievable only with proper tools and experience. Professional installation protects the YG GM8.5-488 and ensures correct performance.

Installation Instructions

1. Safely lift and support the vehicle. Drain the rear differential gear oil.
2. Mark and remove the rear driveshaft and axle shafts.
3. Pull the differential cover and clean the housing completely.
4. Record existing ring gear backlash and pinion preload for reference.
5. Remove bearing caps and pull the carrier and pinion assemblies.
6. Install new pinion bearings from the master install kit onto the YG GM8.5-488 pinion gear.
7. Set pinion depth using shims and a dial indicator to achieve correct tooth contact geometry.
8. Press the new ring gear onto the correct high-ratio carrier and torque ring gear bolts in a cross pattern to specification.
9. Install the carrier, set bearing preload, and adjust backlash to 0.006 to 0.010 inch.
10. Check tooth contact pattern with gear marking compound and adjust as needed.
11. Reinstall cover with RTV or gasket. Fill with GM 8.5 specified differential fluid.
12. Reinstall axle shafts, driveshaft, and wheels, torquing all fasteners to specification.
13. Follow Yukon break-in procedure before sustained towing or off-road use.

Proposition 65 Warning: This product can expose you to chemicals including lead, which is known to the State of California to cause cancer and birth defects or other reproductive harm. For more information go to www.P65Warnings.ca.gov.