89 MT 4x4 Grinding on coast or decel

[fixkick]

My 89 Tracker 2Dr 8V (175K miles with orig. MT and TC) has a nasty grind when I let off throttle.

Repairs/mods of note:
-> new Clutch 2018 incl. good Japanese throwout and pilot bearings.  Maybe 2000km on it since (hunting vehicle)
-> new fluids in tranny (GL-4), diff's and transfer case (GL-5) at that time
-> 3" suspension lift with appropriate 1/2" driveline spacer @ rear diff, running 30x9.5 BFG KO2's
-> new universals throughout
-> this vehicle spends 75% of it's driving time in 4x4, likely 50% of that in 4Lo (except when being towed.  When towed, I stop about every 100km to run the vehicle through the gears with the TC in neutral to splash the top bearing)
-> lots of front end weight with bush guard/winch box/winch and also a SnowSport Plow up front when using to push snow (this is an amazing plow set-up, btw)

The symptoms:
-> metallic grind when I let off throttle.  Not clicking or whining.  Grinding!
-> occurs in 2WD and 4WD, and whether hubs are locked or not
-> worst in 5th, much less in 4th (main shaft needle bearings??)
-> disappears when clutch is disengaged (pedal pushed). Hmmm, can't recall if it still grinds coasting in N.  My recollection is that it doesn't.
-> front diff pinion bearing could be starved of lubrication because the lift kit necessitated topping up higher than the fill hole (I inclined the vehicle and filled it as best I could but it wasn't inclined as high as the lift kit supplier recommended)

The diagnosis:    


Feel free to weigh in...

4th gear is not gear,at all, (key fact) and it just locks up the to main shaft 1:1 ratio.  no load on the cluster below. (neat to know ,trouble shooting)
same thing in the transfer case end to end lock up in  2wd, no load on the chain for it to make noise.

one odd thing on front end locking hubs,  manual or automatic,  the hubs inside rust and you  think the knob set to unlocked is not  working and is 1/2 engaged and makes huge noise.
same with autohubs, you do not have, 1/2 engaged noise.
the test is simple drove the hubs totall,  4 bolt. and drive. (no rain day to keep water from landing there)

front diff bearing does not move ever 2wd, if the hub locks are not bad so, those are first.

remove all screws #6  and the cap it holds totally as  test, and  now the CV shaft go dead, as does the the whole front axle.  (this hubs love to fail and even make huge racket)
and in 2wd mode. so ransfer case does not spin the front axle front pinion at all. and is now dead, not spinning;
GOAL fix 2wd first. 4wd last.  ( I hope parts below are not 14-9 are not GM  tracker parts) below is pure suzuki from Iwata japan or CAMI canada plant.