Transfer case noise when in Reverse with brake on

[fixkick]

I have a 94 sidekick 2dr 8valve with Auto 3 speed 4x4.  When I am in reverse with the brake on I hear a clunking/rattling sound.  I had my wife hold the brake (I was glad she didn't kill me by releasing the brake you never do know do you).  And it was coming from the transfer case.  When you held your hand on it you could feel the vibration.  Could the torque converter be reverberating through the transmission to the transfer case?  Why would the transfer case make that sound when the drivetrain is not even engaged?  In any case when the car is rolling it doesn't make the sound and.  If the car is in 4wd with hubs free rolling it also doesn't make the sound.

Any thoughts?  I will check the fluid tomorrow.  Is this normal?

Thanks

foot brake ON, or hand brake on? which one? or both do this?  IDK?  I guess you  are driving right?  Held hand on what the XFR case lever ?
no not TC,
MY guess is car is not moving, and is  parked and you move the 3L30 box to REverse with foot brake held(?) and then advance the throttle  and you get xfr case noises)
This using throttle test, brakes set is the standard AT box stall test, to flnd bad transmission disc sets (or band clutches) inside that slip.(or a weak engine) sp is valid test done short time.
makes noise in 2wd and 4wd but not with front locking hubs turned to UNLOCKed,
sounds to me a loose chain in the XFR case? or U-joints
why not  assume U-joints and inspect them first they are outside the transmission and x100 times more easy to examine.
ever do this > man handle U-joints under a car, with hands move the JOINTS (forced) turn them first, see if you see movement from UJOINT yoke ends to the STARS.
if those move the bearing inside the joint is super bad. (call bearing clearance PLAY is  bad)
if you then try to move the Prop shaft ends , in 4 directions, 90degrees apart, up, down, left and right and see play in the STAR ends the joint is bad.
I even use  20" 2x4 wood to flex the shaft prop against the body and look very close to the STAR ends for any play at all, play is bad.spin yes, play none allowed.

if the JOINTS are bad (rear) then it will get worse fast, ,  and are dangerous if the front end of rear prop shaft fails, and car Poll vaults. ouch


the transfer case is ENGAGED all the  time  in 2wd or 4wd,  unless in XFR lever  Neutral, 4wd only adds the front AXLE for 4wd front axle actions.
this car has autoadjustiong rear brake pads.  and if bad (most are this old) it will make noise, there.  
if not brake related then Id guess bad U-JOINT rear prop shaft  either end.