NP203 transfer case 101

[LinemanL.U.47]

The NP203 Transfer case. I had some confusion lately with my 203 t-case. After doing some research and talking to a t-case guru I think I have sorted it out. Correct me if any of this is wrong.

STOCK NP203 W/ STOCK HUBS
The 203 is a chain driven full time 4 wheel drive t-case.
Trucks manufactured with the 203 came stock with always locked hubs.
The shift pattern is forward 4 lo lock, 4 lo, N, 4 hi, 4 hi lock closest to seat.
In 4 hi,lo the t-case works like an open diff sending power to the least resistance.
In 4 hi,lo lock the t-case sends power equally to the front and rear.

Many trucks with the 203 t-case have been converted to after market manual locking hubs. The most common reasons for this are price and availability. When your stock always locked hubs fail it can be expensive and hard to find stock replacement parts. I’ve also been told that good after market hubs are stronger than the stock ones. Another common reason is that the t-case has been converted to part time 4 wheel drive (more on that later).

STOCK NP203 W/ AFTER MARKET HUBS
Has all the same characteristics as the all stock set up with a few exceptions.
In 4 hi, lo with hubs unlocked the truck will not move. The T-case would send all power to the least resistance, only the front shaft would spin turning the axles into unlocked hubs.
In 4 hi,lo lock with hubs unlocked the truck will move. Both shafts will turn at the same rate but only the rear will be driving due to the unlocked hubs this is not recommended for daily driving.
A truck with manual locking hubs and a stock 203 t-case should be operated in 4 hi with hubs locked for all normal driving conditions (this is the same as the stock configuration).

Many truck owners to save on fuel cost and wear and tear have converted their full time 4x4 203 t-cases to part time 4x4 cases. The Mile Marker kit is one of the more popular kits.

CONVERTED PART TIME 4x4 NP203 W/ AFTER MARKET HUBS
This NP203 is a chain driven part time 4 wheel drive t-case
Almost all part time conversions are done in conjunction with after market manual hubs.
The shift pattern is forward 4 lo lock, 2 lo, N, 2 hi, 4 hi lock closest to seat.
In 2 hi with hubs unlocked the front drive shaft, diff and axels do not spin. This would be used for normal driving conditions.
4 hi,lo lock with hubs locked would be used for 4x4 driving conditions.

If your truck has manual hubs and your unsure weather or not the t-case has been converted use this simple test. Unlock the hubs and position the t-case one notch down(toward the seat) from neutral. Put it in gear. If the truck moves its been converted, your in 2 hi. If it just revs up it has not been converted, your in 4 hi spinning the front end into unlocked hubs. Hope this info might help someone else out there.