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USA Standard Ring and Pinion Gear Set for GM 8.5in - 3.73 Ratio
The USA Standard ZG GM8.5-373 is a precision-machined ring and pinion gear set engineered for the GM 8.5-inch 10-bolt rear differential. The ZG GM8.5-373 provides a 3.73:1 final drive ratio that is one of the most popular street and mild off-road ratios for full-size Chevy and GMC trucks and SUVs. Every ZG GM8.5-373 set is manufactured from high-alloy steel with controlled heat-treatment profiles that exceed OEM dimensional and material specifications. USA Standard Gear applies rigorous in-house quality evaluation to each ZG GM8.5-373 set covering tooth contact pattern, dimensional accuracy, and material hardness before shipment. The ZG GM8.5-373 is a direct replacement for any vehicle equipped with the GM 8.5in 10-bolt rear end and is backed by a lifetime limited warranty from Yukon Gear and Axle under the Magnuson-Moss Warranty Act.
What's Included
- 1 x Ring gear (GM 8.5in, 3.73 ratio)
- 1 x Pinion gear
- Ring gear bolts
Features and Benefits
- 3.73:1 ratio ideal for towing, off-roading, and performance builds
- High-alloy steel with advanced heat treatment for maximum durability
- Exceeds OEM dimensional specifications for proper meshing and longevity
- Fits 10-bolt GM 8.5in and 8.6in differentials
- 41 ring gear teeth, 11 pinion teeth, 30-spline pinion
- Lifetime limited warranty under Magnuson-Moss Warranty Act
Specifications
| Specification | Detail |
|---|---|
| Part Number (MPN) | ZG GM8.5-373 |
| Axle Application | GM 8.5in / 8.6in 10-bolt |
| Gear Ratio | 3.73:1 |
| Ring Gear Teeth | 41 |
| Pinion Teeth | 11 |
| Pinion Spline | 30-spline |
| Pinion Diameter | 1.625 in. |
| Warranty | Lifetime limited |
| UPC | 883584241584 |
Vehicle Fitment
The ZG GM8.5-373 fits vehicles equipped with the GM 8.5in or 8.6in 10-bolt rear differential, including 1977-1998 Chevrolet C/K 1500 and 2500, 1977-1998 GMC C/K 1500 and 2500, 1992-1999 Chevrolet Suburban and Tahoe, 1992-1999 GMC Yukon and Sierra, and select Camaro and Corvette applications. Always verify your axle tube diameter and carrier bore size before ordering.
Frequently Asked Questions
- Will ZG GM8.5-373 work in both the 8.5in and 8.6in differentials? Yes. The GM 8.6in is the later version of the 8.5in housing and uses the same ring and pinion size.
- Do I need a new install kit with ZG GM8.5-373? Yes. Always pair a ring and pinion replacement with a fresh master overhaul kit for proper preload and backlash settings.
- Will this ratio work with 35-inch tires? The 3.73 ratio works well with up to 35-inch tires on most GM truck platforms while maintaining reasonable highway fuel economy.
- Is ZG GM8.5-373 a standard or reverse-cut gear? ZG GM8.5-373 is a standard-rotation gear set as found in the factory rear axle application.
- Does this include a carrier? No. ZG GM8.5-373 is a ring and pinion set only.
- Is professional installation required? Professional installation is strongly recommended. Gear installation requires precise shimming and backlash adjustment.
- What is the warranty on ZG GM8.5-373? Lifetime limited warranty from Yukon Gear and Axle under the Magnuson-Moss Warranty Act.
- Does ZG GM8.5-373 require a carrier swap? Depending on your current ratio, you may need a different carrier. Consult your axle specs before ordering.
Installation Instructions
Remove the differential cover and drain gear oil. Remove the carrier, pinion, and old gear set. Set new pinion depth using ZG GM8.5-373 pinion and appropriate shims. Install the ring gear on the carrier and torque ring gear bolts to specification. Adjust backlash to 0.008-0.012 inches. Verify tooth contact pattern with marking compound before final assembly. Refill with appropriate gear oil.
Prop 65 Notice
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, visit www.P65Warnings.ca.gov.
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