Yukon Gear High Performance Gear Set For GM 8.5in & 8.6in in a 3.73 Ratio

Yukon Gear YG GM8.5-373 Ring and Pinion Gear Set for GM 8.5 and 8.6 Inch 10-Bolt in 3.73 Ratio

GM truck and SUV owners building for street performance, towing, or tire upgrades who need a proven ring and pinion solution will find the YG GM8.5-373 from Yukon Gear purpose-built for the GM 8.5 and 8.6 inch 10-bolt rear differential. The YG GM8.5-373 delivers a 3.73 ratio in the most popular GM light truck rear axle platform, covering Chevrolet Silverado 1500, Tahoe, Suburban, Avalanche, Trailblazer, S10, Colorado, and GMC Sierra 1500, Yukon, Canyon, and Envoy from 1980 through 2017. Yukon Gear engineers the YG GM8.5-373 from high-grade steel with advanced heat treating and precision tooth surface finish to reduce friction and heat during sustained high-torque operation. The YG GM8.5-373 also covers Cadillac Escalade, Buick Rainier, Regal, and Electra, and Hummer H3 applications sharing the 8.5 or 8.6 inch axle.

Features and Benefits

• High-grade steel construction with advanced heat treating to meet strict OEM and performance specifications
• 3.73 ratio balances towing, acceleration, and tire size performance for GM light trucks and SUVs
• Precision gear tooth surface finish engineered to minimize friction and reduce operating heat
• 30-spline pinion shaft as specified for the GM 8.5 and 8.6 inch 10-bolt differential
• OEM-spec fitment for seamless installation without housing modification
• Compatible with factory carriers, Yukon DuraGrip, and Eaton and Auburn aftermarket differentials
• Broad application coverage from 1980 through 2017 GM light truck and SUV platforms
• Backed by Yukon Gear Y.E.S. extended service protection plan option

Vehicle Fitment

Product Specifications

What Is Included

• One ring gear
• One pinion gear
• Installation instruction sheet

Frequently Asked Questions

What vehicles does YG GM8.5-373 fit?
This gear set fits GM 8.5 and 8.6 inch 10-bolt rear differentials found in Chevrolet Silverado 1500, Tahoe, Suburban 1500, Avalanche, Trailblazer, S10, Colorado, GMC Sierra 1500, Yukon, Canyon, Envoy, Cadillac Escalade, Buick Rainier and Regal, and Hummer H3 models from 1980 through 2017.

Is 3.73 the right gear ratio for a GM Silverado or Tahoe?
A 3.73 ratio is an excellent all-around choice for towing, moderate tire upsizing, and daily driving. It provides more torque multiplied than the factory 3.42 or 3.08 ratio while maintaining acceptable highway rpm.

What is the difference between the GM 8.5 and 8.6 inch differentials?
The GM 8.5 inch was used through model year 1999, and the GM 8.6 inch replaced it in 1999 and newer trucks. Both share the same ring gear diameter and bolt pattern, making the YG GM8.5-373 compatible with both axle generations.

Does installing YG GM8.5-373 affect my factory warranty?
Under the Magnuson-Moss Warranty Act, an installer cannot have your factory warranty voided simply because an aftermarket part was added. The dealer bears the burden of proving that the specific part caused the claimed failure.

Do I need a master install kit with YG GM8.5-373?
Yes. A GM 8.5 master overhaul kit including new pinion and carrier bearings, seals, shims, and a crush sleeve is required for proper backlash and preload during installation.

Can I pair YG GM8.5-373 with an Eaton Posi or Yukon DuraGrip?
Yes. The ring and pinion installs independently of the differential carrier. The YG GM8.5-373 is compatible with the factory open carrier and most performance limited-slip and locking carrier upgrades for the GM 8.5 and 8.6 inch axle.

What gear oil does the GM 8.5 or 8.6 differential use?
Use a 75W-90 or 75W-140 full synthetic gear oil. If a limited-slip or posi carrier is installed, friction modifier additive may be required per the differential manufacturer's specifications.

Is a break-in period required after installing YG GM8.5-373?
Yes. Avoid sustained heavy towing or aggressive operation for the first 500 miles after installation. Change the differential fluid at the end of the break-in period to flush any initial metallic particles from the new gear surfaces.

Installation Instructions

1. Drain the differential fluid and remove the cover, then pull the axle shafts from the housing.
2. Mark the bearing caps for correct reinstallation, then remove the carrier assembly.
3. Remove the old ring gear and clean the carrier flange mating surface thoroughly.
4. Install the new ring gear from YG GM8.5-373 and torque the ring gear bolts in a cross pattern to specification.
5. Remove the old pinion, bearings, and crush sleeve from the housing.
6. Press new outer and inner pinion bearings into position on the shaft and in the housing.
7. Set pinion depth to specification using a depth gauge and the correct shim thickness.
8. Achieve pinion bearing preload within specification using an inch-pound torque wrench.
9. Reinstall the carrier with the appropriate side bearing shims to achieve correct backlash.
10. Verify ring and pinion contact pattern with gear marking compound; adjust shims as needed.
11. Install the differential cover with a new gasket or RTV and fill with the correct gear oil.
12. Break in gears over the first 500 miles before subjecting to full towing loads, then change the fluid.

Prop 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.