NP205: Beefy Transfer Case Made Better
All Inside the NP205
Jay KopycinskiPhotographer
NP205: Beefy Transfer Case Made Better
All Inside the NP205
Jay KopycinskiPhotographer
The NP205 transfer case is a heavy-duty, gear-driven unit manufactured by New Process Gear in Syracuse, New York. It was introduced in 1969 and used until about 1993. The part-time, manual-shift T-case was found in GM, Ford, Dodge, and International Harvester vehicles, and in some construction/industrial equipment.
This transfer case is considered by most people to be nearly indestructible in most applications. The cast iron housing combined with beefy internals puts this case weight at nearly 140 pounds dry. High-range gearing is 1:1, and the NP205 has a low-range ratio of 1.96:1. It was offered in both driver-side and passenger-side front output versions. There were two input mounting configurations: figure-eight racetrack (as shown in the lead image) and a circular six-bolt pattern. Some versions of the NP205 have also been equipped with a gear-driven PTO output.
Multiple input spline counts were available to mate with a variety of factory manual and automatic transmissions. GM cases were always passenger-side front output. The GM SM465 manual versions of the NP205 had a male 10-spline input, and the TH350 automatic mated to a 27-spline male input, both using drive sleeves to mate the transfer case shaft to the transmission shaft. The TH400 automatic versions used a female 32-spline input. Beginning in 1985, GM swapped over to the circular six-bolt pattern with a longer 32-spline input used for both the TH400 and the SM465.
Ford used driver-side front outputs and a divorced NP205 in its trucks from about 1972 to 1977, then changed to a six-bolt pattern married NP205 with a 31-spline female input through 1979. Passenger-side-drop divorced cases were used on Dodge trucks in the early 1970s until a married version with the figure-eight mount pattern came along. Inputs used drive sleeves and were male 23-spline in most cases or male 29-spline when used in the diesel trucks behind the five-speed Getrag manual transmission. International Harvester also used a passenger-drop divorced version of the NP205 from about 1969 to 1975. Note that there were some other weird combinations and custom-order variations with the NP205 that are hard to fully describe, so it's a good idea to fully understand what you have in your transfer case before ordering parts.
Rear output shafts on all versions mate to a 32-spline yoke. The 1979 and older versions used a fixed rear-output yoke, while some later versions often used a slip-style yoke at the tail. Front output shafts were typically 10-spline (early) or 30-spline (late) pieces, with the crossover occurring around 1978. Some Ford and Dodge diesel NP205 cases were optioned with a 32-spline front output.
We spoke with Stephen Watson, an NP205 expert from Offroad Design who mentioned a few items to watch for when looking over an NP205 for use or during a rebuild. For starters, the needle bearing stack between the input gear and output shaft can wear grooves in both surfaces and it’s easy to miss inside the cavity of the output shaft. Check the condition of this surface. You'll often find this wear on trucks with substantial road mileage, but they were seldom or never put in low range. High-mileage transfer cases may have the problem of popping out of low range. This could be due to worn needles under the low gears or wear on the shaft and/or low gear. Cases that have been forcibly shifted into gear may show wear issues on the sliding collar teeth and corresponding teeth on the gears themselves. Note also that drive sleeves on male-input NP205 versions can wear and exhibit a sloppy fit. Eventually, the splines can strip out and fail if used under this condition.
Upgrades to the NP205 are readily available today. They include stronger shafts and yokes, shifter enhancements, and lower gearing options. Another big benefit of the NP205 is the fact that it can now be fitted to many more powertrains. There are the OEM adapter components, but aftermarket vendors have added new adapter components to put the transfer case behind an even wider range of transmissions. The NP205 was manufactured as a stout drivetrain component and, with aftermarket support, can handle most anything an off-roader can throw at it.
