Hi, crew! I posted here awhile ago, and Stjarn made some suggestions, which sounded transmission-related.

I have continually experienced a slight drag/downshift at about 35 mph that didn't exist at 80,000 (now I'm at 125,000). Slight downshift feels the same going from 60-55 or so. This downshift began after the transmission hard clunked once while cold at a stoplight which ran the tach up to 4.5 to get 25mph. My mechanic flushed twice and it never clunked again, but still had that slight downshift at 35.

Out of fear, I put in a 60K used transmission a year ago. After the used trans went it, the car still had the quirky slight downshift so I kept driving, making me think it's NOT the transmission.

Last week, when decelerating, foot off the pedal , the downshift at 35 became HARDER. Apparently the TECH 2 or GM MDI tools in California are hard to come by, which my trusted mechanic doesn't have either. I even tried a Buick and GM dealer who said "that was SO 10 years ago'.

I'm pretty sure I have an AisinAF40-6/TF80SC. VIN YS3GN4AR9B4007988.

Researching online, this transmission also went into Chevy Cruze, Cadillac SRX, but I didn't see much on the Lacrosse. Forum pundits told the owners of these cars that hard down-and-up shifts could be the valve body, which should be rebuilt (with upgraded Sonnax internals) or purchase one new for $900. I 'think' my GM valve body part number is 19256634 or 93183641. Other ideas included: a bad coil, using only Amsoil ATF, and not to use synthetic ATF. (I wouldn't think ATF could be the culprit here)

I love this car at only 125,000, so I'm seriously thinking about having the valve body installed and see what happens. Based on opinions and if the valve body solves it, do I also need gearbox ECU software (also hard to find?) to sync the valve body to the trans?

Thanks a zillion for any guidance!