So this has been going on for a while now.
when shifting from first to second there is a rattling sound from under the center console, and again from second to third but not as noticeable.
mostly it happens when starting up a hill and is not present going down hill.
Could be tranny mount if it sounds like your 4wd lever is buckling in the floor boards, is there vibration? There comin to fail, put a bar on your tranny and see if she wiggles. If it is it can take out your pas. side engine mount. go poly!
i recently had the same problem with a rattle at certian rpms and shifting, mine wound up being the cat was bad. the core was busted and rattling. easy to fix either cut behind cat about 2-3 inchs. grab long metal bar or long screwdriver and break up what is left of internals of cat and remove all that is loose. get a exhaust band clamp and reattach the cut exahust with exhaust band clamp. hope this helps...