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GMC Sierra 1500 GMT800 (1st Generation Sierra)

1999–2006 · GMT800 · truck

The GMT800 Sierra launched for 1999 as the first truck wearing the Sierra nameplate, replacing the GMC C/K. Mechanically identical to the Silverado GMT800, with the same 4.3L Vortec V6, 4.8L LR4, 5.3L LM7, and 6.0L LQ4 V8s, all Gen III small-block iron-block Vortec engines. No AFM in this generation. The Sierra-only Denali trim debuted on the GMT800 with the C3/Denali AWD variant introducing all-wheel drive on a full-size half-ton.

Watch out: Rust on cab corners, rocker panels, and rear wheel arches in salt-belt states. Owner reports of intake manifold gasket leaks on 5.3L LM7 and 4L60E transmission wear at higher mileage.