So... Took my car into the shop today.
Around a year and a half ago I had a strange sound happening at highway speeds. Slight low roaring, which would change in pitch with speed rather than with RPM. So I figured it to be on the back side of the transmission or in the differential. (2017 Cadillac CTS V-sport). Of course the Caddy transmissions are now "sealed self contained" which means you can't even check the fluid levels without putting it up on a rack. So a year and a half ago I took it to the dealer who had always been solid in the past. Their only solution "Replace the whole transmission, $16k" with no explanation as to what was actually wrong. I told them I'd have to think about it, so button her back up and I'd pick her up. Apparently in the "checking" they did something which fixed the roaring sound. So I kept on Truckin...
Now a year and a half later it's back. My suspicion now is a very slow transmission fluid leak, that in this case takes around a year to get low enough to have any effect. No effect on shifting, or driving, just the low roar sound. The car is also right at 100k miles, so time for the 100k maintenance and spa day. I take it into a shop I've discovered since (that was the last time I went to the dealer for anything, and this shop was recommended as great by some fellow CTS owners I have talked to.). Going to fix the transmission, get front end bushings replaced, the usual 100k check over, new plugs and a tune up.
Anybody want to place bets on how much the bill will end up being?