The Heavyweight Hero: Why I’m Digging into the NP203

Hey guys, Josh here.

Looking back at some of the older projects in the shop, I realized I never really gave the NP203 transfer case its fair shake on the blog. If you’ve spent any time around 70s-era half-ton or three-quarter-ton trucks, you’ve likely encountered this cast-iron beast. At first glance, it’s easy to focus on the “pain” side of the equation—and believe me, there’s some weight to that argument. Literally.

The Pain: A Heavy, Thirsty Anchor

Let’s be real: the NP203 is heavy. We’re talking nearly 200 lbs [00:20]. Dragging this thing onto the workbench is a workout I didn’t ask for! It’s also a chain-driven, full-time 4WD case [00:33]. Back in the day, that meant your front end was always spinning, which is a total “budget killer” at the gas pump [01:09].

However, there’s always a fix if you’re willing to wrench. If you’re running one of these in your rig, you can actually find a Mile Marker part-time kit [01:22]. It’s an affordable way to convert the case so you aren’t burning extra fuel when you’re just cruising to the trailhead.

The Victory: The “Doubler” Secret

So, why am I sweating over a 200-lb hunk of iron? Because the NP203 has a hidden superpower: The Range Box [00:40].

The front section of this case is a gear-reduction box that can be detached from the chain-drive mess. The “victory” here is taking that low-range box and mating it to an NP205 transfer case. This creates a “doubler” setup, giving you a 2:1 and a 4:1 low range [00:52]. It’s the ultimate budget-builder hack for serious crawling.

Josh’s Tech Tip: Grab ’em While You Can

These cases are getting harder to find in the scrap yards, so if you spot one for a good price, snag it [02:13]. Even if you don’t use the whole case, that range box is gold for a future project.

I’m about to tear this one down to get that box ready for my NP205 [02:44]. It’s a bit of a grind, but that’s the fun of it—taking something “undesirable” and turning it into a piece of custom trail tech.

If you’ve got questions about the 203 or the doubler setup, drop them in the comments. Let’s get to work!

Wheel it, Wreck it, Wrench it, Repeat!