← All Articles
Dana 300 Transfer Case: The One Part That Won't Betray You
Drivetrain

Dana 300 Transfer Case: The One Part That Won't Betray You

Jason
Jason • March 12, 2026

The Dana 300 is the gold standard of CJ transfer cases, found in 1980-1986 models. It's cast iron, gear-driven, and nearly indestructible — which is good because everything else on your CJ is actively trying to break. Consider the Dana 300 the one reliable friend in a vehicle full of acquaintances who owe you money.

Why the Dana 300 Is the Best Part of Your CJ

Compared to the earlier Dana 20 (1972-1979 CJs):

  • Cast iron case — you could use it as an anvil in a pinch
  • All gear-driven — no chains to stretch or break (looking at you, NP231)
  • 2.62:1 low range — decent stock crawl ratio
  • Centered rear output — whoever designed the offset Dana 20 output should be in jail

If you have a Dana 300, congratulations. It's probably the only thing on your CJ that doesn't need immediate attention. If you have a Dana 20, I'm sorry. Keep reading anyway.

Identifying Your Dana 300

Key identifiers:

  • Cast iron housing (slap a magnet on it — if it sticks, you're golden)
  • Bolted directly to the back of the transmission
  • Two shift levers on top
  • Will be covered in a healthy patina of gear oil because nothing in a CJ stays dry

Common Issues (By Which I Mean Basically Nothing)

Leaking Seals

The most common "problem," if you can even call it that. Output shaft seals weep over time. If this is your biggest concern, you don't own enough CJs.

Seal part numbers if you insist on fixing it:

  • Front output: National #710552
  • Rear output: National #710553
  • Input shaft: National #473204

Twenty minutes, a seal pick, and a hammer. The cheapest repair you'll make on your CJ this year. Savor it.

Worn Shift Forks

If you can't get into gear, the shift forks are probably worn. This requires a teardown, but the parts are cheap. The labor is free because you're doing it yourself in your garage while your wife watches Netflix and pretends you don't exist.

Vibration

Almost always NOT the transfer case. Check your U-joints, driveshaft angles, and slip yoke first. I know you want to blame the transfer case because it sounds more impressive, but it's probably a $12 U-joint.

Twin-Stick Conversion: The First Mod That's Actually Worth It

The twin-stick conversion separates the Hi/Lo and 2WD/4WD controls into independent shift levers. This lets you run front-wheel-drive only — genuinely useful on tight trails.

What you'll need:

  • Twin-stick kit (JB Conversions or Advance Adapters): $200-300
  • About 3 hours
  • A beer for after (budget separately)

After installation you get four modes:

  • 2-Hi — normal driving (the 30 minutes a year you drive on pavement)
  • 4-Hi — four wheel drive, high range
  • 4-Lo — four wheel drive, low range (the real reason you own this thing)
  • Front-Lo — front wheel drive only, low range (for when you need to make a 47-point turn on a cliff)

This is one of the few modifications with a near-100% satisfaction rate. Install it, love it, and then explain to your wife why you needed two shifters instead of one. "It's a safety thing" usually works.

TeraLow 4:1 Kit: Because 2.62:1 Isn't Low Enough

For serious off-roading, the TeraLow kit replaces the stock low-range gears with a 4:1 ratio. Combined with 4.10 axle gears and 33" tires, you'll be able to crawl up a vertical wall at idle.

The kit runs $600-800. Your wife will ask what it does. You'll say "it makes it safer off-road." This is technically not a lie. She won't buy it. Buy the kit anyway.

Maintenance (The Easiest Section You'll Ever Read)

  • Fluid: 80W-90 GL-5 gear oil, about 4 pints
  • Change interval: Every 30,000 miles or annually (you'll forget and do it every 50,000)
  • Check level: Every oil change (you won't)
  • Linkage: Grease the pivots occasionally (you definitely won't)

The Dana 300 asks almost nothing of you and gives everything in return. It's the Labrador Retriever of transfer cases. Treat it right and it'll take you anywhere. Neglect it and it'll still take you anywhere, just slightly more grumpily.

Finding One

If your CJ has a Dana 20, you can swap in a Dana 300. They bolt to the same transmissions (T-150, T-176) with the correct adapter. Used Dana 300s go for $300-600 depending on condition and whether the seller knows what they have.

Pro tip: The guys who list them as "transfer case, don't know what kind" on Facebook Marketplace are where the deals are. Bring a magnet and a flashlight.