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Transfer Case ID Guide

NP203

The New Process 203 was used in GM, Ford, and Dodge through the 70's behind auto and manual transmissions.  They were originally a full time 4WD 'case, meaning all 4 tires receive power at all times. This was made possible through use of a differential in the back of the 203 that let the front and rear driveshafts turn at different speeds as just as a diff in an axle lets each axleshaft turn at a different speed.

For off road use, the 203 had a "lock" position in which the differential was locked making the front and rear outputs spin at the same speed.  Shift positions are: High, Lo, High Lock, Low Lock and Neutral.
A popular modification to the 203 was to install a "part time" kit to eliminate the differential.  In this configuration the 203 operates like more conventional transfer cases in that it's either in 2WD or 4WD and when in 4WD the power is evenly split from front to rear.

The NP203 is identified by several features:

1. The transfer case is made up of 4 sections bolted together, a range box (the gear reduction we use for the Doubler kit), the chain case which houses the chain drive to the front driveshaft output, the differential housing, and the output housing. The front 2 sections are cast iron, the back 2 sections are typically aluminum.

2. The overall length is about 22-23" from the face of the case to the rear output yoke centerline.

3. The shifter is a somewhat complicated box that actuates the 2 levers on a single shaft on the side of the range box section of the 203.

4. The model tag (if it still exists) will be found on the front of the chain case above the front output shaft. It will list the model number, the manufacture date and the gear ratio.

NP205

The New Process 205 was also used extensively in GM, Ford, and Dodge.  GM and Dodge used the 205 in some trucks into the early 90's, Ford stopped using the 205 in 1979.  The 205 is a part time 4WD 'case, meaning when it's in 2WD the front driveshaft will not receive power.  It has 4 stock shift positions, 2wd Hi, 4WD Hi, Neutral, and 4WD Lo.


NP205 cases had several different configurations with Ford and Dodge using both married and divorced models and GM using many different input spline types and 2 different bolt patterns.

The NP205 is identified by several features:

1. The transfer case is one piece of cast iron.  There is a short bearing retainer/output housing at the tail of the case, and aluminum bearing retainers/seal retainers at the front and rear outputs but the working parts are all in a single iron housing.
 
2. There is a small idler shaft cover on the back of the 205 with 3 small bolts holding it on.  This is somewhat unique among transfer cases.

3. The overall length of the NP205 (in fixed output yoke versions) is about 12-13" from the front of the case to the center of the output yoke.

4. The shifter is a very simple lever operating a crossbar between the two shift rails that plunge in and out of the front of the case.

5. The ID tag is found above the front driveshaft output, and will list model, manufacture date and gear ratio.

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Doubler™ Dual Transfer Case
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