So much information... I will begin absorbing.
Can't thank you enough....Oh wait, I CAN make a donation
I have a raspy grinding noise in 4x4, high and low. Same noise with hubs locked or not locked in 4x4. Same noise but less volume in 2wd with hubs locked. Quiet in 2wd high and 2wd low (car has custom twin stick shifter).
Once removed from the car, the needle bearing that uses the front drive shaft collar as the inner race sounds gritty and raspy. I did run the car on a hoist ( yes I have one) and a stethoscope is loudest at bottom in the area of this bearing.
Swapping cases means moving crawler gears to new case along with the twin stick to "new" case.
I have already done this swap. The "new" case also had a raspy sounding needle bearing when, on the bench, the driveshaft was engaged and rotated so I repeatedly flushed it with brake cleaner and light oil followed by some shop air and it now sounds pretty good. All the other bearings sounded and looked good. I am hoping it was simply some grit from poor handling or storage in the needle bearing and all will be OK, but I also aware this may not be the case so I am attempting to do some preemptive planning. BTW, other cases/bearings I have examined do not have this raspy sound. The "new" case is not yet reinstalled into the car because it needs a new boot for the twin stick (entry point for sand and grit?).
To this point i have had almost the entire T case broke down pretty far. I have also found there are two different sizes of speedometer gears on the main shaft. There may also be two different methods of locking that gear to the shaft (a small ball or splines); I have only seen the "balls" in the four cases I have had apart in the last couple of weeks. The different gears are identifiable by the type of speedo output without splitting the cases: mechanical and electrical speedo outputs use different gears.
There are also different splines , that engage the drive shaft, on the rear output shaft. Fine splines on earlier models and course GREEN splines on the later ones.
The shift collars that run it the forks also need to be indexed correctly (I will probably run across this information in your suggested reading material). I have not seen it in any of the aftermarket Tcase instructions. I found it the hard way.
I have not had the main shaft completely out a case but I have had the front gear section completely taken apart (to clearance "new" case and install crawler gears) and i have split the back section on two cases to swap speedo gears on mainshaft and a third parts case I was given to examine/experiment with. I have also taken the front output shaft assembly from a case along with the chain and reinstalled with the chain. So I am getting to know these cases fairly well.
I have a 20 ton shop press, bridgeport, and other fabrication equip. My pipe collection is never large enough and is currently being eclipsed by my transfer case parts collection LOL. I have access to slide hammer, pilot bearing puller that might fit, and if need be a lathe.
The stumbler I have is the access to the needle bearing. It is seated from the inside against a shoulder that is right behind the seal. The shoulder and entire bore where the bearing sits have two slots in them that are sort of across from each other. I assume this is to allow access for some small hooks on a pilot bearing style puller and allow lube to the seal. There is no way to drive that bearing out with a pipe as the out race is pretty much hidden behind the shoulder. Mill back the shoulder?
I removed one needle bearing assembly from junk case with a brass drift but it was not pretty and no chance of bearing survival. I have considered a plate with threaded rod made to pull endwise though both slots as a puller toward the inside of the case. Bearing survival??
Thanks for the response I will study the information you have provided and update if I can add any new information.
Scott