4 wheel drive low problems

I have a 96 Grand Cherokee 5.2 liter v8, quad track. My 4 wheel drive works great in high, but when I try to engage the 4wheel drive low, it gives me a load of problems. First off, I have to pull the lever back as slow as I can, because if I go too far or all all the way down, it shifts into nuetral. When I do get the panel to say LO meaning it worked, it only runs in low for about 25 seconds before it once again shifts into neutral. Its not the lever doing it because I held it in 4LO one time and it still shifted into nuetral by itself. Someone told me that whatever connects to that bar is lose and I need to tighten it. What do you think could be causing this. I really need to fix it myself cause there is no way I could afford to get it looked at right now.

get underneath the jeep look at the shift linkage for the TC, there shopuld be 2 shift rods connected by a bracket, whic connects into the frame and into a bracket on the tranny, the center rod (bracket) prolly came out of either the frame end or the tranny end.

Or the shift linkage itself could need adjusted.

This may be obvious, but you aren't using 4lo on hard pavement. There should always be some slippage on the ground when using 4lo.