Dana 300
Usage: '80-'86 Jeep CJ-5 and CJ-7.
Notes: Jeep and Scout versions are available and are not interchangeable due to bolt pattern. Short and long versions also exist but the short version is considered stronger. Offers 2.62:1 low gear ratio and an aluminum tail housing, a 1--inch intermediate shaft, and a 23-spline input shaft. It uses helically-cut gears in a cast iron case. The Dana 300 uses a passenger-side front output.
Weaknesses: Weak output shaft in all versions, tail housing is also prone to cracks, failure. Low gear ratio is lacking.
Strengths: Versatility, strength, and parts availability. A great transfer case for many applications. Can also be flipped and used for driver-side front output applications. Twin-stick capable. Aftermarket cases of greater strength are available as are low gear sets and front and rear output strengthening parts.
The Dana 18 is the granddaddy...
The Dana 18 is the granddaddy of Jeep transfer cases. It was used in many Jeep models from 1940 to 1971 and was also used in some Scout vehicles. We like the Dana 18 for its factory twin-stick operation and available PTO, but it's also a simple gear-driven assembly that can be serviced and repaired by most users with moderate mechanical skill. Many variations of the Dana 18 exist with differences in intermediate shaft length and input gear tooth count.
Dana/Spicer Model 20
Usage: Jeeps vehicles '62-'79, Ford Bronco, and Scout.
Notes: 2.0:1 low gear ratio. Uses a cast iron case with a six-spline, 29-tooth, 1--inch intermediate shaft. Passenger-side drop in the front and center output in rear. Variations exist in shift linkage with some early models equipped with twin-stick shifters. Ford Bronco version is driver-side drop at both outputs with 2.46:1 (early models) and 2.34:1 (later models) gear ratios.
Weaknesses: Low gear range is lacking. Tail shaft strength is questionable.
Strengths: Versatility and parts availability. Durable, compact, and lightweight. Twin-stick capable. A simple yet strong transfer case that has proven its ability in 1-ton Jeep J-trucks.
Dana/Spicer Model 18
Usage: Jeep vehicles up to 1971, Scout
Notes: Cast iron case with passenger-side drop in front and rear. Early versions use weaker -inch, six-spline intermediate shaft with later models upgraded to 1-1/4-inch 10-spline shaft. Variance in locating bore when mated to Buick V6 engine. Early Scout versions were equipped with twin-stick shifter. Gear-driven transfer case with 2.46:1 low ratio. Accepts PTO or overdrive. Strong and versatile transfer case. Will also accept Dana 20 gears.
Weaknesses: Low gear range is lacking.
Strengths: PTO capable, lightweight, and durable. Twin-stick capable. Easy to work on. Legendary.
Toyota transfer cases are...
Toyota transfer cases are extremely versatile and can be used in a variety of configurations. Marlin Crawler sets up Toyota 'cases in single, dual, and triple configurations to further reduce the low gear range and create the ultimate low crawl ratio.
Toyota Pickup/4Runner
Usage: '79-'95 Toyota Trucks and 4Runners.
Notes: Many variations between years. Both gear- and chain-driven units exist. Gear cases use seven bolts in rear case half; chain cases have five bolts. As a general guide, '79-'83 cases used top-shift gear-driven units and '84-up rigs used forward shift gear and chain-driven units (depending on engine and transmission). Later models also use an oil cooler that is plumbed to rear of case. Early models are passenger-side front output; later models use driver's side front output. Gear ratios include 2.28:1, 2.57:1, and 2.66:1.
Weaknesses: Low gear range is lacking. Front and rear input/output shafts are of questionable strength. Weak die-cast aluminum case.
Strengths: Versatility and parts availability, twin-stick ability, dual, triple, and crawl box capable.