will_w204

CPO car, records show trans service was done at 50-something thousand miles, no record of 39k, but that doesn't mean it wasn't done, just no record of it......likely wasn't........

Anyway, when cold, when accelerating very slowly, sometimes trans with upshift from 2-3 with a soft thud, and at extreme low RPM, like 1200 in 3rd. Additional to this is an occasional upshift (again, under light throttle) where the revs increase in between a shift. Doesn't feel like a "slip," but something is off. Both happen consistently each week at some point.

About a year and a half, and oodles of miles left on the warranty. Any suggestions?

alx

If no errors are logged - tcu adaptations need to be reset. You're might have learned some garbage. Also tcu version needs to be checked. If never updated you are a rev or 3 behind.

If errors are logged- the dealer will diagnose accordingly

will_w204

Thanks; no errors last time, but this did all start AFTER they updated to the most recent rev in December for another issue.

alx

ah, if problems after version update that is a good indication that gear adaptation for 2nd and 3rd gear has not been performed or was performed, but drifted the wrong way and got stuck

have the dealer redo the transmission adaptation

also they need to make sure the tcu version matches the correct ecu version (ie both are the latest and greatest)

and check tranny fluid level

1xsculler

How do you check the tranny fluid level? Where is the plug to put new fluid in the tranny after you've drained the old, R&Red the pan and installed a new filter?

alx

It is not a user friendly procedure. Level is checked via an overflow tube through the filler in the tranny pan. This is done at specific fluid temp and requires a fluid pump and proper adapter. Essentially you pump fluid until it comes out of the overflow tube (and goes down your arm and drenches you lol)