The Chevy SSR engine, transmission, and TORSEN differential


The second engine: a 6.0 liter with 390 horsepower (LS2)

The new LS2 engine features a deep-skirt aluminum block with cast aluminum heads, delivering 390 horsepower and 405 lb-ft of torque for quick acceleration from any speed. A six-speed manual Tremec transmission is now available, showing that GM means business.

Chevy SSR with designer Andre Hudson

The first engine: a new aluminum version of the Vortec 5.3

GM started with an aluminum Vortec 5.3 liter engine with its Hydramatic 4L60-E automatic transmission; the aluminum version dropped 100 pounds from the truck version. The block uses 319-T7 aluminum alloy, aiding heat rejection, and was produced by the gravity-poured sand casting process so steel cylinder liners could be cast in-place.

Quiet-profile pistons minimized clearances as the pistons rocked; they were polymer-coated to reduce cold scuffing and engine noise, and provide enduring wear surfaces. The deep-skirt engine block design, with six-bolt main bearings, allowed cross bolting of the bearing caps, limiting flex and vibration. The cam was in the block.

SSR 6.0 liter V8 engine

The engine met California Ultra Low Emissions Vehicle (ULEV) standards without EGR. It used 100,000 mile spark plugs and 150,000 mile coolant.

The transmission

The Hydra-Matic 4L60-E transmission, an electronically controlled, updated “turbo 350,” was used in many GM cars (including the Corvette) and some light duty pickups. (In 2005, the 4L65-E replaced the 4L60-E, and a manual became available.) The Toledo-built transmission had a 300-mm torque converter and weighed 195 pounds.

The TORSEN differential

The TORSEN Traction Differential on the rear axle distributes power to the wheel with the most traction, in theory before any wheel slip can occur. It was similar to the Camaro’s design and worked with the engine-based electronic traction control. The axle ratio was 3.73:1.

Most differentials are passive designs, using clutches and the inertia of wheel-spin to engage and transfer power to wheels with traction. TORSEN units use a gearing system that reacts faster.

The torque distributing effect of the TORSEN differential is a constant, proportional to the torque on the axle. With minimum torque on the axle, differentiation occurs freely as with an open differential, making it easier to maneuver when both rear wheels are on a slippery surface. When operating the vehicle with unequal traction under the rear wheels, the TORSEN differential will apply about 65-70% of the total axle torque to the wheel with the greater traction.

In cornering, the differential biases torque to the outside wheel after the inside wheel becomes saturated with torque and begins to slip. The result is smooth handling, strong traction and quicker and safer lane changes. The system is made by a subsidiary Bosch.

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