Early Bronco Dana 20 Transfer Case

Early Bronco Dana 20 Transfer Case Guide

All 1966-77 Ford Broncos came factory-equipped with the rugged, gear-driven Dana 20 transfer case. While these units share the same foundation, there are important differences between early and late versions that matter when ordering parts, rebuilding, or planning drivetrain upgrades. Whether you're restoring a stock Bronco or building a trail rig, understanding your Dana 20 is key to getting the performance you expect.

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

The most noticeable difference between Early Bronco Dana 20 transfer cases comes down to shifter design and low-range gearing.

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 moves in a simple forward and backward pattern and is often preferred for its slightly lower 2.46:1 ratio, offering a bit more control off-road.

1973-77 Bronco – J-Shift Dana 20

• 2.34:1 low-range gear ratio

• Backwards “J” shift pattern

The J-shift uses a curved shift path. While the low range is slightly higher than the earlier version, the difference is minimal for most driving situations.

Internal Differences Between Early & Late Dana 20s

Beyond the shifter and gear ratio, there are key internal differences between 66-72 and 73-77 Dana 20 transfer cases that directly affect parts compatibility.

Key differences include:

• Front output shaft design

• Bearing variations

• Shift rails

• Detent components

These variations make it critical to identify whether you have a T-shift or J-shift case before ordering rebuild parts.

Dana 20 Transfer Case Rebuild Kits

Rebuilding your Dana 20 is a smart move when servicing your drivetrain, especially on higher-mileage Broncos or rigs that see regular trail use.

WILD HORSES Dana 20 rebuild kits are designed to simplify the process by including all required bearings for both early and late models. You may end up with a couple of extra bearings, but you won’t get stuck mid-build with the wrong parts.

Basic Dana 20 Bearing & Gasket Kit

• Bearings

• Gaskets

• Seals
  Ideal for a standard refresh when major components are still in good shape.

Deluxe Dana 20 Overhaul Kit
Includes everything in the Basic Kit plus:

• New cluster shaft

• Thrust washers

• Shims
  A solid choice when addressing wear in critical internal components.

Super Deluxe Dana 20 Rebuild Kit
Includes everything in the Deluxe Kit plus:

• Adapter housing bearing
  Best suited for complete rebuilds or long-term reliability.

Gear Ratio Calculation: How Low Can You Go?

One of the strengths of the Dana 20 is how well it pairs with low first-gear transmissions and deeper axle gearing to create strong crawl ratios for off-road use.

To calculate crawl ratio:
Transmission First Gear × Transfer Case Low × Ring & Pinion Ratio

Example 1 – NP435 with Dana 20
6.69 × 2.34 × 4.11 = 64.34:1
That’s roughly 64:1—plenty capable for most trail situations.

Example 2 – Adding a Dual Transfer Case (Super Crawler)
6.69 × 2.00 × 2.34 × 4.11 = 128.68:1
Now you’re at approximately 128:1, delivering serious slow-speed control for technical terrain.

The Dana 20 transfer case has proven itself in 1966-77 Ford Broncos for decades thanks to its durability and straightforward design. Whether you're running a stock T-shift, rebuilding a J-shift, or dialing in your crawl ratio for off-road performance, understanding these differences ensures you get the right parts and the results you’re after.

If you’re unsure which Dana 20 you have or what rebuild kit fits your needs, the WILD HORSES 4x4 team can help you identify the right components and get your Bronco back in shape.