1000/M74 2011-2012 Chevy/GMC Silverado/Sierra 3500 HD 6.6L RWD – Remanufactured 6-Speed Automatic Trans

Description

Configured for 1-ton highway freight, GMC Sierra 2011-2012 Remanufactured Transmission units handle 6.6L Duramax turbo-diesel output in 2WD 3500 HD dual-rear-wheel chassis. This remanufactured 6-Speed Allison 1000 unit manages 460 continuous horsepower, 660 lb-ft maximum torque, and an engine ceiling of 4000 RPM while maintaining internal line pressure of 230 PSI.

Heavy die-cast A380 aluminum casing encases 3 planetary gear trains formed from heat-treated 8620 steel. Segmented graphite friction plates with high-flow fluid grooves suppress heat across all internal clutches. Precision-reamed Gen-4 valve body bores house hard-anodized aluminum sleeves to stop internal hydraulic pressure leakage. Sump capacity measures 14.5 quarts of certified automatic transmission fluid, utilizing 1/2-inch cooler lines. Total dry weight measures 325 lbs, fitted with a balanced lockup torque converter.

Key Features of GMC Sierra

Fleet operators choose to buy GMC Sierra 2011-2012 remanufactured transmission units to maintain dependable highway freight transport in 1-ton 2-Wheel Drive chassis. Factory remanufacturing restores strict valve body tolerances and guarantees solid clutch holding capacity across all 6 forward gear speeds.

• 8620 steel planetary gearsets handle continuous 660 lb-ft Duramax diesel torque without gear tooth deflection.
• Segmented friction discs dissipate localized heat to stop clutch plate burn in stop-and-go diesel routes.
• 14.5-quart fluid capacity keeps hydraulic circuits cool under prolonged interstate commercial hauling cycles.
• 2011-2012 Sierra replacement valve body eliminates hydraulic cross-leaks across double overdrive gear steps.
• Sierra 2011-2012 torque converter package locks fast under load to eliminate slip during highway acceleration.
• 6-Speed gearing provides dual overdrive ratios spanning 3.10:1 in 1st gear down to 0.61:1 in 6th gear.
• 230 PSI maximum line pressure clamps clutches tight to prevent intermediate friction plate slippage.

1-Ton Highway Propulsion Thermal Dynamics

High-displacement internal oil pumps maintain line pressures between 190 and 230 PSI, holding operating fluid temperatures within 165°F to 195°F. Input torque absorption handles 660 lb-ft at 1600 RPM without clutch slippage. A gear reduction range from 3.10:1 in 1st gear to 0.61:1 in 6th gear overdrive keeps Duramax diesel engines inside their peak torque band while cutting cruising engine RPM. The transmission cooler loop sheds excess BTUs through 1/2-inch ports, protecting planetary thrust washers from excessive heat wear.

2-Wheel Drive Driveline Slip Interface

A 34-spline rear output shaft links straight to the driveshaft slip yoke. Rear extension housing bushing runout is verified under 0.0018 inches with a dial indicator, avoiding driveline shudder under load. Die-cast case mounting pads align flush with standard GM crossmembers, keeping driveline pinion angles true under maximum chassis payload.

Dynamometer Load Screening Maintenance Schedule

Every unit undergoes dynamic testing on an automated spin dyno under full diesel engine load simulations to calibrate 6-Speed solenoid shift points, verify cooler port flow rates, and evaluate lockup clutch hold. This transmission is not engineered for competition pulling trucks, bracket drag racing rigs, or operation with blocked radiator heat exchangers.

• Check transmission fluid level and color using the dipstick every 14 operating days.
• Drain and replace synthetic automatic fluid plus external spin-on filter every 25,000 miles.
• Flush transmission fluid cooler circuits every 12 months to prevent friction particulate buildup.

Diesel Driveline Warranty Crate Contents

A 3-Year unlimited mileage warranty covers commercial fleet operators against mechanical and hydraulic defects nationwide. The heavy wooden transport crate contains the complete remanufactured automatic transmission, a dynamic-balanced lockup torque converter, an external spin-on filter, installation paperwork, cooler flushing guidelines, and fluid specification documentation tags.