Early Bronco Dana 20 Transfer Case

Early Bronco Dana 20 Transfer Case Buyer’s Guide | 1966-77 Ford Bronco

All 66-77 Broncos came factory-equipped with the Dana 20 transfer case. While they may look similar at a glance, there are important differences between early and late versions that matter when ordering parts, rebuilding, or planning gearing upgrades.

If you're restoring, rebuilding, or modifying your Early Bronco drivetrain, here’s what you need to know.

T-Shift vs J-Shift: What’s the Difference?

The most notable difference between Bronco Dana 20s is the shifter design and low-range ratio.

1966-72 Bronco – T-Shift Dana 20

• 2.46:1 low-range gear ratio

• Straight up-and-down shift pattern

• Early 1966 models used a round shift knob

• Later 1966-72 models used a push-button T-handle

The T-shift pattern moves straight forward and backward through the ranges. These early Dana 20s are often preferred for their slightly deeper 2.46 low range.

1973-77 Bronco – J-Shift Dana 20

• 2.34:1 low-range gear ratio

• Backwards “J” shift pattern

The J-shift version uses a curved shift pattern that resembles a backward “J.” While the low-range ratio is slightly higher (2.34 vs 2.46), the difference is minor for most drivers.

Internal Differences Between Early & Late Dana 20s

Beyond the shifter and gear ratio, there are internal differences between early (66-72) and late (73-77) Dana 20 transfer cases.

Key differences include:

• Front output shaft design

• Bearing variations

• Shift rails

• Detent components

These differences matter when ordering rebuild parts. Always confirm whether you have a T-shift or J-shift case before purchasing components.

Dana 20 Transfer Case Rebuild Kits

Rebuilding your Early Bronco Dana 20 is a smart move if you’re already servicing the drivetrain.

WILD HORSES Dana 20 rebuild kits include all bearings required for both early and later model cases. Yes, you may end up with two bearings you don’t use — but this ensures you won’t be stuck mid-rebuild without the correct parts.

We offer three levels of rebuild kits:

Basic Dana 20 Bearing & Gasket Kit

• Bearings

• Gaskets

• Seals

Ideal for a standard refresh when hard parts are still in good condition.

Deluxe Dana 20 Overhaul Kit

Includes everything in the Basic Kit plus:

• New cluster shaft

• Thrust washers

• Shims

Recommended if your cluster shaft shows wear or you want added insurance during rebuild.

Super Deluxe Dana 20 Rebuild Kit

Includes everything in the Deluxe Kit plus:

• Adapter housing bearing

Best for complete rebuilds or higher-mileage transfer cases where maximum longevity is the goal.

Gear Ratio Calculation: How Low Can You Go?

One of the biggest advantages of the Dana 20 is its ability to be paired with low first-gear transmissions and deeper axle gears for strong crawl ratios.

To calculate crawl ratio:

Transmission First Gear × Transfer Case Low × Ring & Pinion Gear Ratio

Example 1 – NP435 with Dana 20

NP435 first gear (6.69)
× 2.34 (Dana 20 low range)
× 4.11 ring and pinion

= 64.34:1 crawl ratio

That’s roughly 64:1 — very respectable for a trail-driven Bronco.

Example 2 – Adding a Dual Transfer Case (Super Crawler)

NP435 first gear (6.69)
× 2.00 (Super Crawler)
× 2.34 (Dana 20)
× 4.11 ring and pinion

= 128.68:1 crawl ratio

Now you're at approximately 128:1 — serious slow-speed control for technical terrain.

The Dana 20 transfer case is a durable, gear-driven unit that has served 1966-77 Ford Broncos well for decades. Whether you’re maintaining a stock T-shift case, rebuilding a J-shift unit, or calculating crawl ratios for a trail build, understanding the differences ensures you order the correct parts and get the performance you expect.

If you're unsure whether you have a T-shift or J-shift Dana 20 — or which rebuild kit is right for your Bronco — the Wild Horses team is ready to help you identify the correct components.