The 242 transfer case shifter pushes against a spring and the spring pushes the gear collar.
if there's any mismatch front to rear - tire sizes, wear, air pressure - the collar won't slide and it won't go into 4wd - no matter what the selector says.
you can generally get to 4wd fulltime - because that keeps the differential action front to rear - but not part time or 4 low.
also the linkage isn't great - and it can wear and be misaligned too - I haven't had the problem but several other folks have.
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2005 CRD
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