Transfer Case for General Motors with Auto Trac

Description

Managing active automatic four-wheel traction, GM AutoTrac 4WD Transfer Case packages handle 320 continuous input horsepower alongside 340 lb-ft torque at 5200 RPM. A wet multi-plate clutch pack modulates front axle torque on demand during slip, while heavy planetary gearing yields a 2.72:1 reduction ratio with dash button selection for off-road pulling power.

Die-cast magnesium alloy AZ91D forms the split casing to isolate internal rotating components from frame twisting under load. Carburized 8620 steel helical gear sets incorporate crown relief teeth to suppress gear chatter. Multi-disc friction clutch packs operate inside an oil bath to transfer torque forward without slip. Threaded casing ports take standard hex plugs, with the reservoir holding 2.0 quarts of AutoTrak II blue fluid. Dry weight measures 86 lbs.

Key Features of GM AutoTrac

Fleet managers buy GM AutoTrac 4WD transfer case units to restore automatic four-wheel drive performance on commercial pickup trucks and sport utilities. Each remanufactured unit receives an upgraded rear case half with a pump rub protector plate to prevent puncture leaks.

• A 2.72:1 low-range gear set multiplies engine torque for pulling heavy trailers out of mud
• Internal wet clutch packs direct front axle torque within fractions of a second upon wheel slip
• Precision GM AutoTrac 4WD transfer case bearings control internal shaft deflection during continuous towing
• Multi-link steel drive chain links maintain high tensile strength under full throttle acceleration
• Hardened 27-spline or 32-spline female input shafts mate flush with automatic transmission output shafts
• Upgraded rear case housing incorporates anti-wear clip protection to eliminate oil pump rub failures
• Viton output shaft seals prevent fluid migration between transmission and transfer case reservoirs

GM AutoTrac Dynamic Torque Limits

Operating fluid temperature remains stabilized between 150°F to 185°F under full payload and towing conditions. The internal clutch pack channels up to 450 lb-ft continuous input torque at 3200 RPM without thermal slip. A 1.00:1 high range ratio provides smooth highway speeds, while low range planetary gears provide 2.72:1 torque multiplication for maximum off-road traction. Heat radiates through the external ribbed magnesium casing, preserving fluid film thickness under continuous medium duty truck operations without auxiliary fluid coolers across demanding commercial worksite environments.

Driveline Slip Yoke Alignment Specs

The rear output features a 32-spline slip yoke barrel that accommodates long rear suspension travel. Front output shafts terminate in a 1310 or 1350 series universal joint companion flange held to 0.002-inch dial indicator runout limits. A 245 mm drop center distance directs power straight to the front axle differential.

Shift Motor Service Inspection Protocol

Shift actuation uses a dash selector switch wired to an external 12-volt encoder shift motor mounted on the casing. This transfer case package is not engineered for full spool solid locked front axles, dry pavement low range turning, or vehicle flat towing without rear propshaft disconnect.

• Inspect shift motor electrical harness connectors for moisture or corrosion each shift before operating
• Check fluid level at the casing upper fill plug every 250 operating hours
• Drain and replenish fresh AutoTrak II fluid every 12 months of severe commercial service

GM AutoTrac Crate Package Manifest

A 2-Year commercial limited warranty protects all internal planetary gears, clutch plates, and bearings against failure. The heavy wooden shipping crate contains the remanufactured transfer case unit, new electric shift motor, fluid drain plug, fill plug, and factory installation setup instructions for complete fleet maintenance integration.