Engine/Transmission (1994 - 1998) transmission/transfer case rattle

[Piersol]

Finally broke down and took my truck to the dealer to find the dreaded rattle. I put a new spring in the TC shifter, hose on the shaft, earplug under the knob to no avail. Pulled the shaft and found the TC snap rings in place. It only does it in OD so I think it is the OD crapping out on me. The noise is so faint you can't hear it with the radio on or the windows down, or even if it's raining. The dealer says everything is fine. "it just has alot of miles on it" Would an oil analysis of the transmission fluid show if the OD is going south? The transmission itself was rebuilt at 80,000 miles.