The split case (small idler shaft) on my 60 (5.3 Vortec) has been fine for the 70k miles my swap has been done also. I have rebuilt it a few times due to silly stuff happening like needing to replace the t-case tranny seal, and wrecking it, but it has been fine otherwise. I've never seen anything wrong with it. I too have not been kind to it. LOTS of hard driving, lots of bouncing off of redline in the desert, snow, dry pavement, wet pavement, and Drag races from lights. I even went through a phase where It was fun to do burn outs with the 35's, but the clutch didn't really like it so it kinda quit grabbing that well after a while. It still grabs great, just not quite like it did. Anyways, the T-Case (and H55 for that matter) has held up pretty well.