Jeep Vehicle 2 Letter Model Designations / Model Codes

by Quadratec

If you've ever wondered why people call a certain year Wrangler a "TJ" or "YJ" instead of just Wrangler, well, it is because each year range vehicle has a certain in-house designation that engineers use for categorization.

These Jeep letter codes trace back to World War II military contracts, when Willys-Overland and Ford needed a fast way to track different prototypes and production runs. Over the decades, that internal shorthand carried over into civilian production, so every CJ, YJ, TJ, JK, and JL you see today still follows the same Jeep letter designation system.

Below, we'll break down every Jeep 2-letter designation code by category, from wartime prototypes to the newest Wrangler and Gladiator models.

Key Takeaways

• Every Jeep model has its own letter code, such as YJ, TJ, JK, or JL, that engineers use instead of the marketing name.
• Military prototypes like the GP, GPA, and GPW came first, establishing the letter-code system Jeep still uses today.
• The CJ series (Civilian Jeep) spans 1944 to 1986 and includes 12 separate model codes, from the CJ 2A flatfender to the CJ 8 Scrambler.
• Knowing your Jeep's exact code, not just "Wrangler" or "Cherokee," is the fastest way to confirm correct parts fitment.
• Current production Jeeps use the JL (Wrangler) and JT (Gladiator) codes.

Military and Prototype Jeep Designations

Long before Jeep became a household name, it was a military project. This early group of codes includes the AJ prototype military Jeep, believed to stand for "Advanced Jeep," along with the GP prototype that led to the first production Jeeps built for the U.S. Army. It also covers amphibious and Willys-built wartime variants like the GPA amphibious jeep and GPW Willys jeep, plus the MA, MB, MC, MD, and MDA codes that mark the evolution of military jeep designations from World War II through the Korean War era.