At A Glance
Model: Dana 20
Design: Part-time, gear-driven, iron-case, centered rear output, passenger-side front output
Found in: '72-'79 CJs, '67-'73 Jeepsters, '63-'70 Wagoneer/Gladiator/J-Trucks (and '71-'79 with manual transmissions)
Available stock ratio: 2.03:1
Use it with: Smaller Jeeps with up to a decent small block or fullsize Jeep with stock powerplants
Flat tow: Put the transfer case in Neutral, put the transmission in gear or Park, leave the driveshafts attached
Modifications: Tera Low 3.15:1 low range, twin stick with old Dana 18 or aftermarket parts, 32-spline Advance Adapters rear output
Identify: Cast-iron rear tailhousing and an oil pan
Dana 300
Come 1980, AMC was making its version of the Jeep more and more plush with car-like transmissions, carpeting, A/C, automatic transmissions, and so on. So it is a surprise that among all these things with nothing to do with off-road ability, the company also came up with the Dana 300.
Basically, it is a beefed up, updated version of the Dana 20; the 300 was bigger and had fine spline output shafts, yet retained the gear-driven, iron-case durability of the past designs.
The 1980 unit had a shorter rear tailhousing than later units, which is nice for driveshaft angularity until you learn that the speedometer mount is different than later Jeeps and the bolt pattern of the tailshaft housing is different, which precludes some heavy-duty upgrades.
At A Glance
Model: Dana 300
Design: Part-time, gear-driven, iron-case, front passenger-side offset output, rear centered output, one stick for range and 2WD/4WD selection
Available stock ratio: 2.62:1
Use it with: Depending on how it's built, almost any Jeep. Wouldn't advise it for the heavier ones (5,500 pounds and above) with any combination of aftermarket parts
Flat tow: If your case is in the stock orientation, remove your rear driveshaft from the axle and fasten it out of the way. If you've clocked it flatter than stock, you may get away with the same method mentioned for the Dana 20. Basically, it needs to have at least one gear on the rear output in the pool of oil so it slings the oil around when the Jeep is moving. In the stock clocking setup, this doesn't happen
Modifications: Twin stick setup, JB Conversions Lo-Max 4.0:1 low range for the increase in strength where needed, and heavy-duty 32-spline front and rear outputs
Identify: Its got a centered rear output, oil pan, and an aluminum tailhousing
New Process 200
It's a rare one, that's for sure. The NP200 is a divorced case that is a direct predecessor to the venerable NP205. If you stumble across one, your first clue will be the yoke where the female input should be. The next clue will be that it's big and heavy. After that will be the owner giving it away because it tends to overheat.
Mainly found in the M-715s, it was also seen in DRW Jeep trucks in the 1960s and early 1970s. Neither one is a particularly common or high-mileage vehicle, but they are still revered in the Jeeping community. These trucks tend to sit in fields and next to garages until someone digs them out and bribes the current owner enough to let go of their "project."
Fast forward 30-40 years, and you've got a divorced transfer case that, while near bulletproof, only has a 1.96:1 low range and, in about 60 percent of them, there are overheating issues when driven on-road at or near the top speed of 55 mph for any distance.
This overheating is commonly attributed to straight-cut gears, but this is a misnomer. There are, in fact, helical-cut gears in this transfer case. Their pitch isn't quite what the NP205 has, but they are indeed curved. The overheating could possibly be attributed to lack of use and pitting and galling of the internal components, courtesy of the environment and lack of usage.
At A Glance
Model: New Process 200
Design: Part-time, gear-driven, iron-case, front and rear passenger-side offset output, twin stick operation with front axle engage/disengage and high/low range options
Found in: '67-'69 M-715, M-724, M-725, M-726, and circa '60s and '70s DRW J-Trucks
Feed it: 85W-90 gear oil or heavier
Available stock ratio: 1.96:1
Use it with: If you can get over the meager low range and luck upon one that doesn't overheat or don't care about on-road manners, you can run this case in any size FSJ you want with a swapped-in 2WD transmission. Because it is divorced, it won't fit SWB Jeeps (under 105-inch wheelbase or so) well at all.
Flat tow: Transmission in gear or Park, transfer case in Neutral. Note: If your particular case doesn't handle high speeds when being driven, it won't when being towed either. Besides, what would you flat tow an M-715 with? A 5-ton?
Modifications: Swap the center-mounted parking brake with the offset rear output for some relief from the heat problem. Put in lower axle gears to decrease the speed of the case
Identify: It's big. It's divorced-mounted. It's leaking. It's got a band-style parking brake on it. It's cast iron. You try to lift it and worry about medical repercussions. Fill all these, and you've got yourself an NP200
New Process 205
This is the big Maha transfer case. Cast -iron, gear-driven, used in 1/2-, 3/4-, and 1-ton trucks from Chevy, Dodge, and Ford for more than two decades, this case can take whatever beating your little Jeep can throw at it.
It can be easily mated to many Jeep transmissions with shade tree ingenuity or aftermarket support. If you are having issues blowing up driveshaft yokes, 1410-style yokes can easily go on this case, it can be twin-sticked without difficulty, and common speedometer senders fit all of them. They are available with any number of input spline counts and configurations, driver-side and passenger-side drops, and divorced and married styles. This is the bulletproof transfer case of your dreams-you can't destroy it.
The problem? The low range is only 1.96:1, its heavy (like really, really heavy), and fitment can be a problem with earlier Jeeps because it's a physically big case.
At A Glance
Model: New Process 205
Design: Part-time, gear-driven, iron-case, aluminum output and input retainers, front passenger- and driver-side offset output available, rear center output, stock single-stick operation with 2WD, 4WD high, and 4WD low options
Found in: Early '70s to early '90s Chevy, Dodge, and Ford pickups
Feed it: 85W-90 gear oil or heavier
Available stock ratio: 1.96:1
Use it with: If you can fit it and don't mind the added weight and the huge overkill factor. Chances are, you won't break it
Flat tow: Transmission in gear or Park, transfer case in Neutral
Modifications: JB Conversions Lo-Max 205. It's got a 3.0:1 low range, even heavier duty than the big-block handling stock gears, and relatively conservative pricing. Again, if it'll fit in your Jeep and mate with your transmission, this is the last transfer case you'll ever need
Identify: Look for the identification tag on the back of the case first. If you can't find that, look between the cover on the rear of the case for the input shaft and the rear output for a small, round cover. This cover will be equidistant between the two and covers the intermediate shaft. It'll have three bolts holding it in. If it's got a cover there with three bolts holding it on, snag it