74 Blazer (jimmy) Problems?

I recently bought a '74 GMC Jimmy.
It's got the NP203 case with a Milemarker part-time kit installed.
Two problems I have are:
4-low doesn't seen to be working. It goes into 2-low but in 4-low, it
doesn't lock the front shaft. 2-high & 4-high seem to engage fine. Could
this just be a linkage problem? Or would that be too easy?
Second is: In 4-high, the front tires jerk when turning. The tighter the
turn, the harder it jerks. This can't be normal. Or is it?
Sorry for the lack of knowledge, but I've been dealing with 2wd desert
buggies for the last 20 years & I needed something a little bigger & slower.

Thanks in advance for any help.
Brett

Well if it is jerking when turning, it must be in 4wd something....
most 4wd systems are part time 4x4 and not actually intended for hard dry
pavement..so this is normal....try an older Explorer if you really want to see
some jerking....binding more like...
Does is move in 4Lo...grinding noises??
It has to go thru transfer case N to get to lo, so if it is not going in alll
teh way it will grind badly and vehicle wont move...