I had the very same question with my 3550 which was ten years old with 8000 miles on it. I drained and replaced the GM synchromesh
oil and sent the old stuff in for analysis. They reported high wear metals but said that was normal for a new transmission. They also reported 1.4% insoluables ( sludge) which they said was high. The attributed this to aging of the
oil.
Physically the old
oil was much darker and thicker then the new stuff.
I have been taking samples on all my cars when I change oil. It has proved useful. For example I had some head work done which require me to remove and reinstall the heads. The oil analysis picked up small quanties of stuff they said likely came from
antifreeze. I started looking and sure enough I was getting a little leakage out of the head gasket. I retorqued the heads, ran it for a while and sent in another sample. No indications of leaking so far.
Another good example is my dodge truck. The oil analysis found very high bearing material counts. I have owned this truck since new. Time to consider getting another.
Rule of thumb: Never buy a used car from a guy that has his oil analyzed. He may know something you do not!
For Sale: 1994 dodge truck.......