Officially debuting back in October 2022, the 2024 GMC Sierra HD introduces a mid-cycle refresh to Big Red’s heavy-duty pickup line that includes exterior revisions, an overhauled cabin and a plethora of new tech goodies. Despite these various improvements, the HD truck is currently unavailable with E85 FlexFuel capability for the time being.
The E85 FlexFuel capable feature (RPO code FHS) has been unavailable since the start of regular production (SORP). Normally, this feature is a $100 option on the Pro trim level only, and not offered at all on any other trims.
In addition, this feature is only available with the 6.6L V8 L8T gasoline engine, and requires choosing the $275 trailer brake controller (RPO code JL1) as well.
As of the time of this writing, it’s unclear when E85 FlexFuel capability will be available to order again.
As a reminder, the mid-cycle refresh of the 2024 GMC Sierra HD is highlighted by the introduction of the range-topping Denali Ultimate trim level. An all-new 2024 GMC Sierra HD AT4X is also in the pipeline for introduction later this year.
In regard to powertrain specifications, the 2024 Sierra HD utilizes the 6.6L L8T V8 gasoline engine as standard on most trims, while the 6.6L V8 L5P turbodiesel Duramax engine is optional on most trims. The Duramax boasts 470 horsepower and 975 pound-feet of torque, up by 25 horsepower and 65 pound-feet over the pre-refreshed models. In the case of the Denali Ultimate trim, the Duramax is featured as standard.
Regardless of engine option, every GMC Sierra HD is equipped with the Allison-branded 10-speed automatic transmission as standard fare, which replaces the GM six-speed previously found in gasoline-powered configurations.