Np203 help
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Senior User
Joined: Jan 2003
Posts: 310
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Np203 help
I just recently acquired a 1978 F250. I am assuming that it has the NP203 T-case. Any way how do I work the whole 4hi, 4hi-loc, etc.etc.... What do I want when I'm on the street or on the trail. thanks in advance.
Laughing Gas
Joined: Apr 2001
Posts: 1,191
Likes: 4
From: West Union, OH USA
Np203 help
on those, they're in 4wd all the time when in a lock position. its also in 4wd until you reach 35 mph in what ever the other position is. so its imposible to burn the rear tires pretty much. try to find a part-time conversion kit. would be better off for gas mileage.
Senior User
Joined: May 2001
Posts: 133
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Np203 help
The 203s have a differential in the transfer case. In 4 hi, the transfer case will distribute power to the axle that needs it (one not slipping). When you select 4 lock, the t-case differential is locked and both axles are equally powered. Obviously the same operation applies to the 4 low and lock, with the low range now in use. I'm not sure about the 35 mph defeat in 4 hi; it's pretty much defeated on dry pavement anyway. I believe the design was for full-time winter driving conditions (ice) and possibly the precursor to auto-lock hubs. Rules that apply to the 203: Don't use 4HI-Lock or 4LO-Lock on the street.
