The spread of General Motors’ eight-speed automatic transmission through the GMC Sierra 1500 lineup is nearly complete. Introduced to the Sierra in 2015 paired only with the biggest engine available, a 420-hp 6.2-liter V-8, the eight-speed has since become an option on certain Sierras equipped with the 5.3-liter V-8, tracing a path through the Sierra […]
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