Gargantuan GMC Sierra HD roughened-up with new AT4X

With Chevrolet having showcased the off-road focused Silverado 2500 HD ZR2 last month as its most capable heavy-duty bakkie to date, it was only a matter of time before upmarket sister brand, GMC, did the same with its version, the Sierra HD.

Unveiled this past weekend in the States, the Sierra HD AT4X, like the ZR2, is the work of parent company General Motors (GM) teaming-up with American Expedition Vehicles (AEV) to create what GMC calls “a truck that enables adventurers to go further while still having the towing capability essential for heavy duty haulers”.

Off-road with 300 mm

The third AT4X branded model after the “compact” Canyon AT4X and the Sierra 1500 AT4X, the modifications involved transforming the regular Sierra 2500 HD into the AT4X includes a heavy-duty steel front bumper and 18-inch alloy wheels wrapped in 35-inch Goodyear Territory all-terrain tyres.

Underneath, GMC has fitted a heavy-duty aluminium skidplate to protect the engine and a steel item below the transfer case, while introducing a 38 mm suspension lift-kit as well as position sensitive spool valve dampers sourced from Multimatic.

The result is a claimed ground clearance of 300mm like the Silverado ZR2 – unsurprisingly a lot more compared to the Canyon AT4X’s 272 mm – with the final upgrade and unique touch being new front and lower control arms, plus model specific steering knuckles.

ALSO READ: Chevrolet goes off-road crazy with mammoth Silverado 2500 HD ZR2

In addition, the Off-Road mode from the Silverado has been carried over and thus adjusts the transmission, stability control, traction control and ABS when activated.

If the regular AT4X still isn’t enough, buyers can opt for the Extreme AEV Edition that effectively takes the places of the ZR2 Bison.

In this instance, the AEV’s added accommodations consist of stamped steel bumpers, a factory fitted winch, expanded steel underbody protection underneath the steering box, AEV badges and 18-inch Salta alloy wheels.

Inside

Inside, both the AT4X and AEV retain the 12.3-inch digital instrument cluster and 13.4-inch touchscreen infotainment system, as well as the 15-inch Head-Up Display and driver assistance items ranging from Adaptive Cruise Control to a transparent camera-view for the fifth wheel or gooseneck towing mount.

Bespoke to both models though are grained leather seats with heating, ventilation and massaging functions for the front chairs, a special Obsidian Rush colour scheme, a 12-speaker Bose sound system, ash wood decorative inserts and American Expedition Vehicles branded floor mats on the AEV only.

Pick your V8

On the power front, the Sierra HD AT4X offers the same engine choices as the Silverado 2500 HD ZR2, namely a 6.6-litre petrol V8 outputting 299kW/629Nm, or the 6.6-litre Duramax turbodiesel V8 delivering 350kW/1 322Nm.

The only transmission available for both is a heavy-duty column-shift mounted ten-speed Allison automatic. Payload and tow ratings meanwhile are identical to that of the Silverado.

Look on and drool South Africa

Going on-sale in the North American autumn that runs from September to November, no pricing details for the Sierra HD AT4X was revealed, but while 2024 will see the standard Silverado 2500 HD heading to the Australia with right-hand-drive, the GMC will remain US-bound and therefore sold only with left-hand-drive.

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