I think the transfer case in my truck might need some attention . It will not engage 4High over 35mph. Just growls at me . I hope I didn't hurt anything at the last truck pull .
I think it's probably slack in the chain . It does work fine . It just won't shift on the fly either by maintaining speed or accelerating or slowing down.

 

im not sure about that.. but mine has had a problem lately where if i havent used it in awhile.. it wont engage if i come to a stop.. such as if i get stuck in 2wd.. i'll switch it in 4hi and it wont go in.. if i put it in 4hi or lo and drive around for acouple minutes it'll finally engage itself

 

Really ... a few MINUTES? I'll (sometimes) have to drive around for up to ... say ... 10 seconds or so before mine will engage (or disengage) but never TOO long. Sometimes the light comes on (or goes out) immediately.

 

Mine made a clunking sound every few yards when it went to hell. The dealer GMC dealer sold it to me with no oil. So much for the multi-point inspection. I did get a brand new one straight from dodge installed at the dealer at no charge. Sure works great now.