Quite a bit of insight here.
The easiest way to identify your transfer case, looking at the back of the case where the rear driveshaft yoke is located, focus your attention slightly to the right of that and if you see a 3-bolt cover about 2 inches in diameter it is a NP-205 (NP= New Process, as in the company that manufactured these transfer cases- New Process Gear.)
If there is no 3-bolt cover it is the NP-203 full time.
There are kits sold to eliminate the full-time functioning of the 203.
The chain in the 203 is contained within the larger of the two housings which make up the 203 the other (the front) is the range box with the gearing to allow low range.
The NP-203 utilizes a differential to allow slippage between the front and rear drive shafts and eliminate binding and subsequent parts breakage. Removing the front driveshaft, or unlocking the hubs on a vehicle with an unmodified NP-203 can be temporarily overcome by simply locking the shift lever into the "hi-loc" position
The general rule of thumb (not exactly accurate though) automatic transmissions were equipped with the NP-203, and the four speeds were equipped with the NP-205.
The TH-350 transmission was equipped with the NP-205 before the 203 was put into production for the 1973 model year.
If there is anything specific you would like to know about your truck just PM me and ask away, I have owned nearly 30 of these truck over the years.
Most likely your trucks' VIN# goes like this CKR147F followed by 6 numbers.
C= Chevy, K=4 wheel drive, R= 400 engine, 1= 1/2-ton, 4= regular cab,
7= 1977 model year, F= Flint, Michigan. assembly plant (this COULD be one of 7 plants, but most likely because you have the 400 engine it came from Flint, I could still be wrong here though.
The 6 numbers following the above information is the sequential serial number given while on the assembly line, some years and some plants started their production runs at 100001 instead of 000000.
Last edited by M&M CUSTOM; 07-13-2004 at 08:28 AM.