No Low

Long story short, I picked up a 95 yj this spring, I tried 4HI on the test drive and it seemed to
work. I got it running right and safe enough for the wife to run around town in a few days
but got hurt at work and really have not had a chance to touch it again till today.
So tonight I tried to go to 4LO but cant get it. I got through 4HI and into neutral but cant get lo,
got back into 4HI with some grinding.
Is there a trick? I tried fwd, nut, rev.
Poss. the vacume lines? Linkage?
As you can guess this is my first Jeep
I have had several 4x4's 92 Toyota, 85 Bronco and my 97 Z71 they all have there quirks
but never had this problem.
If it was up to me I'd just park it for now but the wife wants to drive it this winter instead
of the GMC "it's tiny and easy to park" Grrrr