If you are thinking the transmission should be bolted directly to the skid plate, you're mistaken. Sounds like someone replaced the stock rubber transmission mount with a poly one. Got a picture of it? That will clear things up.
'84 CJ-17: 17" stretch, locked Toy axles, 5.5" lift, FI, AX15, D300 w/twin sticks, boatsides & junk.