Revolution Gear & Axle GM 10-Bolt 8.5in/8.6in 3.42 Ratio Face Hobbed Ring & Pinion Set
The 3.42 ratio is what GM put under a huge number of Silverado, Sierra, Tahoe and Suburban half-tons, so most people looking at the Revolution Gear & Axle GM10-342DC have a 10-bolt rear that has started to howl and want the same ratio back. Others own a 3.08 truck that went up a tire size and now feels flat pulling away. This is a new 3.42 ring and pinion for the GM 8.5 in. and 8.6 in. 10-bolt, cut face hobbed and lapped the way current OE gears are made.
The pinion turns 3.42 times for each turn of the ring gear and axle shafts. Revolution lists this set as standard rotation with a 30-spline pinion, an 8.5 in. ring gear and 10 ring gear bolts of 7/16 in. thread, made from 8620 steel. Face hobbed, sometimes called 2-cut, gears have equal tooth height from heel to toe, which Revolution says lowers noise and raises load capacity compared with older face milled designs. It also changes setup: the face hobbed backlash range is tighter than a 5-cut set's, covered below.
Compared with a 3.08, a 3.42 gives about 11 percent more torque multiplication at the wheels. That is almost exactly what a 10 percent taller tire takes away: a 3.08 truck moved from 30 to 33 inch tires behaves like a 2.80, and 3.42 gears put it back near the original 3.08 feel.
Gear whine changes with load; a wheel bearing growl usually changes when you swerve gently left and right. Check the glove box RPO sticker: GU6 is a 3.42 axle and GU4 is a 3.08. Our guide to finding your axle ratio shows how to count teeth if the sticker is gone, and the GM 8.5 10-bolt problems and rebuild cost guide covers what else fails at the same time.
Revolution lists this set by axle, the GM 8.5 in. and 8.6 in. 10-bolt, rather than by vehicle. In practice that is the 8.6 rear in 1999-up Silverado and Sierra 1500s and their SUVs, plus the earlier 8.5 used in GM cars, C/K trucks, Blazers and 1977-1991 K-series front axles. The carrier break for this family sits at the 2.56/2.73 end, so a 3.42 fits the 2.73-and-up carrier most of these axles already have. Count 10 cover bolts and confirm the ring gear is 8.5 in.; the 8.2 in., the Oldsmobile 8.5 and the 2010-2015 Camaro IRS 8.6 are not the same axle. Send us your year and VIN if in doubt. The 10-bolt gear kit buyer's guide helps match kits, and more parts are under rebuild kits. If you are going up two tire sizes, the 3.73 version of this set is the better match.
| Brand | Revolution Gear & Axle |
| Part number | GM10-342DC |
| Fits | Revolution Gear & Axle GM 10-Bolt 8.5in/8.6in 3.42 Ratio Face Hobbed Ring & Pinion Set |
| Type | Ring & Pinions |
| Condition | New |
| Ships | Same business day (in stock), from the USA |
| Warranty | 1-year |
Doing this repair right usually means replacing these at the same time. Same transmission, ships together.
No. A 3.42 replacing a 3.42 keeps the speedometer and shift points correct. Reprogramming is only needed when the ratio or tire size changes.
Usually not. Revolution puts the carrier break for this family at 2.56/2.73, so axles that came with 2.73 or deeper gears keep their carrier.
Face hobbed (2-cut) gears have equal tooth height heel to toe and use a tighter backlash range, 0.004-0.007 in. on Revolution's chart, than older 5-cut sets.
Do not assume so. The 2010-2015 Camaro uses an independent 8.6 rear that is a different axle from the truck 10-bolt. Send us the VIN before ordering.
A master overhaul or bearing kit for your axle years, a cover gasket, and 75W-90 GL-5 gear oil, plus friction modifier if the carrier is a clutch-type posi.
