If your t-case is full time you must have the NP-203. These are considered to be "weaker" than the NP-205, 208...because they are chain driven rather than gear. A lot of people think they are an aluminum case which also makes them weaker. If you have ever muscled the 203 out of a truck you'll know they are cast iron. two problems with the 203 are: The chain will stretch and need to be replaced; Also,, being full-time they cause more drive line wear. "Mile Marker" makes a conversion kit that is simple to install. You would also need to istall manual hubs on your axle. Now you have a part-time t-case. This conversion is probley cheaper (?) than switching t-cases and is easy to install. I have had it in my '77 K10 for a long time and it has held up pretty well. Well enough it hasn't failed giving me a reason to swap cases yet. If you go this way remember...Only use 10w-40 motor oil in the case. Other cases use gear oil or tranny fluid. The chain in the 203 slings oil into the rear case (where an oil pump is). Gear oil is to "thick and tranny fluid to "thin" to properly lubricate. This also brings up another point. With the part-time conversion you will need lock your hubs (4x4 not required) for about 10 mile a week. This allows the chain to drive and lubricate the case.
1
