I just bought a 76 k5 blazer but it will not engage the 4x4, the truck has the 203 transfer case, but I was told the lockouts are from a '78. This is my first project truck and I’m not too familiar with 4x4 system, especially with a chain!? The first week I had the truck I tried using hi-loc cause of snow but the rod to the t-case popped out and caused a large whining noise, and I lost all power as the t-case went into neutral. I thus reconnected it but haven’t had the chance to really mess with it. The whining noise is back but only if you try to engage the t-case in a low gear. I was told from the past owner that the truck was very powerful in 4x4, but seemed to distribute more power to the front then the rear, and to disengage the 4x4 he needed to jack the front-end up? If anyone can shine some light it would be deeply appreciated!

 

Man, not knowing what has been done to it in the past... Hopefully someone put a part time kit into it when they installed the front lock out hubs. From the factory, all NP203 trucks had solid bushings in the front hubs permanently engaging the front axle.

The NP203 is a full time 4wd transfer case. When in HI or LO, the differential located in the tail section of the transfer case allowed for different output shaft speeds while turning without binding up the drivetrain like typical 4wd vehicles do while turning with the transfer case locked into 4wd. When in HI LOC or LO LOC, the center differential would lock up providing equal power (and output shaft speeds) to both axles.

A part time kit will do away with the differential in the transfer case making HI & LO into the 2wd modes while HI LOC and LO LOC are the 4wd modes. Combined with lockout hubs on the front axle, it would allow for reduced drivetrain losses while not locked into 4wd (HI LOC or LO LOC).

But enough of the history lesson...

Your problem sounds as though the transfer case is not adjusted properly.

Here is what I found with a quick search: