dlyter, you mentioned incorrect gearing in the front differential. When did you have the new gears put in the rear end and when did transfer cases start breaking in relation to that?
Have you inspected the wear pattern on the teeth of the rear differential gears? I'm thinking you might have some issue with the rear end locking up or putting a serious drag on the drive shaft and you might have some super u-joints that just don't want to break before the transfer case does.
Or maybe it is locked up u-joints. But maybe it isn't because you would have noticed that at least one of the times you had to pull the drive shaft to replace a transfer case.

 

Also, for all who care to do things right, NEVER shift into 4LO on the go... You need to come to a COMPLETE stop, in Neutral on the transmission, THEN shift into 4LO... If it doesn't go in easy, let your foot off the brake and let it roll a couple inches then try again. Otherwise YOU could be the cause of your transfer case failing.

 

And for all those that cringe when it grinds (if it grinds, mine does), do the same but kill the engine after putting the truck in neutral then shift.

 

It was December of 09 when my gears were done. No broken cases until summer of 2011. U joints on the driveshaft got replaced when the first case got done.

 

Your on the right track keep digging, think hyld lock, miss matched wheel speed to t case speed, and when it goes it goes big at the matting of the tranny and t case. Most of his cases had the same thing going on with them, something was causing the same thing with all of them. Why the DS is not failing or the cross joints IDK yet.

And +1 for your second post

 

I'm just hoping this is all behind me once my mega viper is in.

 

I think your problem is AFTER the t-case, unfortunately.... Just a wild stab in the dark here, but, I would wonder if as the rear heats up, it doesn't get into a bind situation, putting more stress than usual on the t-case. Unless you are dropping into gear with the engine at redline, changing the trans isn't going to change anything.

 

No there isn't any neutral drops lol... I guess it could be in the rear but don't know why it would show its head now and not before.. worse come to worse ill be waiting even longer to finish the truck so I can put some 2500 axles under it....

 

I have to agree that it is probably something in the rear.

 

dlyter09

Does the rear end whine, growl, grind? It has to if that's was the cause, if something is binding in the rear diff it will make a good noise.