frame with boxed forward frame rails. The GMT600 chassis was offered in two wheelbases: standard-length 135-inch and extended 155-inch. A replacement for the 110-inch short-wheelbase van (discontinued after 1992) was not included as part of the GMT600 design, as the short-body van had functionally been superseded by the Chevrolet Astro/GMC Safari mid-size vans. For 2003, the GMT600 chassis underwent a substantial revision and was redesignated GMT610. In line with the GMT800 chassis, the GMT610 adopted a three-section fully-boxed frame. With slight modifications, the GMT610 also adopted the front suspension of the GMT800 pickup trucks, with short-long arm front suspension (rear-wheel drive) and torsion-bar front springs (all-wheel drive). In another change, four-wheel disc brakes were introduced, standardizing anti-lock brakes (ABS). In a first for the full-size van segment, the GMT610 platform was also offered with full-time all-wheel drive as an option. Powertrain details At its launch, the Chevrolet Express was introduced with five engines. Shared with C/K pickup trucks, a 4.3L V6 was standard, with 5.0L, 5.7L, 6.5L turbodiesel and 7.4L V8s were options. All gasoline engines adopted the "Vortec" port-fuel injection upgrades for 1996, increasing power and torque outputs; the 6.5L turbodiesel was offered in a full-size van for the first time. All engines were paired with a 4-speed overdrive automatic, carried over from the Chevrolet Van; 1500-series vehicles used a 4L60E transmission while 2500 and 3500-series vehicles used a heavier-duty 4L80E unit. For 2001, the Vortec 7400 was replaced by the longer-stroke Vortec 8100 (at 496 cubic inches, this is the largest-displacement engine ever factory-marketed by Chevrolet); the engine was offered for the Express through 2002. For 2003, the engine lineup underwent a series of revisions, retaining only the 4.3L V6 from 2002. The "Generation III" small-block V8 engines (based on the LS-series engines) were introduced, with the Express receiving 4.8L, 5.3L, and 6.0L V8s. For 2006, a diesel engine offering returned, adopting a detuned version of the 6.6L Duramax V8 (LGH) from the Chevrolet Kodiak. For 2008, 5.3L V8s on 1500-series vans gained flex-fuel (E85) capability. For 2010, 2500 and 3500-series vans used the six speed 6L90 transmission. Coinciding with the discontinuation of the 1500-series, the Vortec 4300 V6 (the final engine derived from the original Chevrolet small-block V8) was discontinued in 2014. After 2016, the 6.6L Duramax diesel V8 was discontinued; a 2.8L inline-4 Duramax (the first four-cylinder in a full-size Chevrolet van since 1964) replaced it