"The transfer case always made noise under deceleration in 2wd,"
This is a common symptom when lifting and or running dual cases in a toyota without a CV drive shaft. To correct this, run a CV shaft with the pinion 2* under the slop of the shaft. Something to look into if this noise on decel persists after the repair.
Marlin's competition 4.7 is the best 4.7 gear set available, in my opinion. 2.28×2.28 duals are probably less likely to fail if you don't need the super low 4.7s. 2.28×2.28 is still pretty low geared.
"It's not a matter of IF it will break, but WHEN it will break." Im not buying this, at least not with a 22re, 37's and some common sense. Power and 40+ tires, probably true.
I wouldn't give up on the RF1A cases but If you actually have built your rig beyond what they can handle you probably want to get away from Toyota cases all together. 
Yeah, I'm just running a 22RE engine and I take it easy when wheeling. I do like having the 4.7 case so I can drive nice slow and controlled through harder obstacles.
It will interesting to see if the deceleration noise disappears after I get it rebuilt and reinstalled. Thanks for sharing your knowledge on this subject.
