2021 Nissan Frontier

The 2005-2021 Nissan Frontier is the D40 generation and had one of the longest production runs of any vehicle in the modern American market, remaining essentially unchanged for sixteen model years. It shares its F-Alpha frame with the Pathfinder and Xterra of the period. Engines were the 2.5-liter QR25DE four-cylinder and the 4.0-liter VQ40DE V6, paired with a five- or six-speed manual or a five-speed automatic. Rear-wheel drive was standard with part-time four-wheel drive optional, across King Cab and Crew Cab bodies. A PRO-4X trim added a locking rear differential and Bilstein dampers.

The very long production run means the truck was thoroughly understood by the time it ended, with a large parts and aftermarket ecosystem. It grew substantially over the D22 and moved into the mid-size class. The D41 generation that followed in 2022 kept the frame but replaced the body, interior, and powertrain entirely.

As a used buy, the D40 is capable and the VQ40DE V6 is durable, but the generation carries one issue that outweighs everything else. The radiator incorporates the transmission cooler, and internal failure mixes coolant with transmission fluid, destroying the automatic. Pink or milky transmission fluid is the telltale sign, and a preventative cooler bypass is a common owner modification. Checking transmission fluid condition directly is the single most important step in buying one of these trucks.