How Does the NP205 Transfer Case Work?
The NP205 was built by New Process of Syracuse, New York and was introduced in 1969. The NP205 was fashioned with a single iron case to house the internal gears. It was a part-time t-case that was a helical gear set (previous transfer cases, like the 203, had internal chains constantly jumping out of guides. The low range ratio is 1.96:1, with the high range being 1:1.
The NP205 T-cases were made with multiple configurations for input shaft positions and different spline counts to fit with the various transmissions manufacturers used. While GM and Dodge were the first to use the NP205 (Chevy’s C10 trucks until 80, and K30 one-tons from ‘81 - ‘91. Dodge on W series trucks). Early NP205s had different spline counts for manual and automatic transmissions (GM manuals had a male 10-spline input, the TH350 (automatic) used a 27-spline input, and the TH400 used a female 32-spline input). Eventually, GM converted and streamlined their automatics (TH400 and SM465) to share a more solid shaft with a 32-spline input.
Ford used a left-hand drop (driver’s side) for output shafts, with a divorced NP205 transfer case for their trucks in the early to mid-70s. The separate transfer case had to sit back farther (requiring a longer driveshaft), raising their 4-wheel drive rigs about 4 inches taller than the competition. This unique T-case ignited owners to refer to the Ford 4x4s as “Highboys.” In 1977, Ford changed to a married transfer case for a couple of years using a 32-spline female fixed input and front output shaft. (Ford moved to the NP208, with slip yoke outputs in 1980, which were great for everyday driving but tended to break when strained).
Dodge used several different versions. They had a passenger side drop with 23 or 29-spline male inputs, which backed up the manual transmissions on diesel trucks. International Harvester used a divorced unit until 1975 but dropped it shortly before Ford did. (All GM, Dodge, and IH trucks had a passenger-side front output shaft).
Is A 205 Transfer Case Good?
The reputation of the NP205 transfer case was that it was virtually indestructible. You simply could not kill it. The existence of gears created much stronger internals, and since the output shaft was a fixed yoke (unlike the slip yoke like the NP208), it tended to stay put under duress (although not always). The NP205 became an instant hit among off-roaders due to its ability to take a pounding. The fact that the NP205 was used in almost every manufacturer’s trucks and that many parts were the same size made it easy to find parts for repairs or modifications.
What Issues Did the NP205 Have?
While the NP 205 may have been the delight of off-road enthusiasts, it did have some issues. Both the input and output driveshaft was prone to failure. The shafts tended to fail by slipping out of their connections, causing the seals to break and the transmission and transfer case to lose all lubricant. Many NP205 vehicles ended up stranded on the side of the road due to the driveshaft failures.
The NP205 was replaced with the NP208 (which is surprising in that it was chain-driven), but the new T-case has serious issues that developed almost immediately when the slip yoke rear output tended to become loose. While some Ford trucks used the NP208, when the 460 V8 emerged, Ford opted for the BW 1345 and 1356 transfer cases made by Borg Warner. GM trucks continued to use New Process t-cases like the NP207, 231, and 241.
How To Identify the NP 205
Several methods can help you identify if you have an NP205 transfer case. (For a more detailed review of identifying an NP205 transfer case, see the article from advanceadapters.com.
The Casing Construction
The NP205 transfer case has a cast iron casing that weighs 140 lbs, while the stock NP208 is made from aluminum casing and weighs about half as much.
Some owners need help identifying the differences between the NP205 and NP203, but there is a way to spot the difference. (The NP203 used cast iron and aluminum to bolt four compartments together - the front 2 are iron, and the back 2 are aluminum). The NP208 transfer case is all aluminum.
(Please note that this method is for the “Doubler” units that involved married units of the 203 and 205).
Bolt Pattern for the NP205
One of the easiest ways to recognize an NP205 is by looking for the three-bolt pattern on the rear idler shaft cover. This design is unique to the NP205 (NP203 and the 208 use a six-bolt pattern. (Both Dodge and GM 205s use identical eight-bolt patterns).
The Identification Tag
If New Process did anything right, it was that they liked to take credit for the transfer cases their Syracuse plant manufactured. There is an ID tag above the front driveshaft with the words “New Process” on it. The 205 designations will be on the model line.
If you have a chance to peek inside the transfer cases, the NP205 was gear driven, while the 203 and 208 used chains. Owners often had trouble with the chains stretching and jumping.
What Is The NP205 Doubler?
Some heavy-duty, highly abusive full-size applications prompted some owners to marry the NP205 to the front gearbox of the NP203. The two units use an adapter to produce the married “Doubler” unit. The advantage is super lower gear ratios that “double” the lower gear from 2:1 to 4:1. For more information on the NP205 Doubler, see the Motortrend article here.
About THE AUTHOR
My name is Matt and I've been around cars all my life! I have owned and worked on many different classic vehicles, so I started this site to share my experiences. If you're new to classic cars, then this website is for you.Read More About Matt Lane