New Process NP203

NP203 Transfer Case Specs & Information

The chain driven, full time NP203 transfer case is often faulted for its power robbing, gas guzzling characteristics. While it has its inherent flaws aftermarket modifications, such as a part time conversion, can increase the transfer case's desirability. While it'll never be on the same level as the NP205, it's a perfect match for doubling with the stout gear driven case and the resulting compounded low range is particularly appealing. You'll find the NP203 in a number of GMC/Chevrolet, Ford, and Dodge fullsize pickups.

The New Process 203 Transfer Case is a fullsize, full time, chain driven transfer case. General Motors, Dodge, and Ford all used the NP203 in select 1973 - 1979 pickup applications. It's unique in that it is a full time transfer case, meaning that the gear train contains a differential that splits power between the front and rear axles in the same way that an axle with an open differential splits power between the left and right tires. Therefore, engine power is not necessarily equally split between the front and rear axles while driving. The transfer case does have a locked setting for both low and high range operation, which locks the differential, disabling the full time behavior and equally transmitting power between the front and rear axles. GM and Dodge cases used the same bolt patterns, while Ford had its own design. Despite being chain driven, it is a relatively robust system, though not nearly as desirable of its brother, the NP205. The factory shift positions are (from front to back): Low Lock (Loc) - Low - Neutral - High - High Lock (Loc).

As it is a full time case, fuel economy is significantly reduced over a part time transfer case such as the NP205. The answer to this problem is a part time conversion, for which parts and kits are readily available. This essentially disables the full time power split between the front and rear axles, making the transfer case behave like a part time unit. While the factory shift pattern is Low Loc - Low (full time) - Neutral - High (full time) - High Loc, a converted transfer case will have the options 4 Low - 2 Low - Neutral - 2 High - 4 High. While full time operation allows for favorable control in low traction conditions, converting to part time operation greatly reduces power loss through the transfer case and noticeably increases fuel economy.

It is common to see NP203/NP205 "doublers", which is quite literally a NP203 mated to a NP205. More specifically, the process mounts the range box (not the entire transfer case) of a NP203 to the input side of a NP205, using machined adapters to mate the parts securely. This accomplishes many things - first and foremost, it allows for up to a 3.94 to 1 reduction (2.01 for the NP203 x 1.96 for the NP205, often advertised as a nominal 4:1) with low range engaged in both transfer cases, effectively doubling the gear reduction of a standard NP205 transfer case. Furthermore, it eliminates the potentially problematic and less favorable chain drive system of the NP203. Doubling the two cases require only using the NP203's helical geared reduction box, NOT the entire drive system. Doubling the two cases is an affordable technique in order to retain an extremely stout gear train while reaping the benefits of a compound low range setup.


NP203 Specs


New Process Gear


Full time, chain driven transfer case.


• 1973 - 1979 GMC/Chevrolet fullsize
• 1974 - 1979 Dodge fullsize
• 1974 - 1979 Ford fullsize

Case Material:

Primarily cast iron with some aluminum components. The case can be divided into 4 sections - the range housing (cast iron), chain housing (cast iron), differential housing (aluminum), and output shaft housing (aluminum). The case is around 22" to 23" long.

Shift Type:



Married and divorced - married NP203's are much more common.


High Range:

1.00 : 1

Low Range:

2.01 : 1

Input Splines:

10, 23, 27, 31, or 32

Pass/Driver Drop:

Driver and passenger side drops


~ 200 lbs

Fluid Type*:

10w-30 or straight 30w motor oil


ID tag located above front output shaft.

*Required fluid type and fluid capacity may vary with application and model year - refer to vehicle's owner manual.


New Process NP203 exploded view