I've noticed some odd shifting from my ZF transmission lately during mild/moderate deceleration and acceleration. Example: cruising at 30mph with a moderate acceleration will result in the tach needle (engine rpm) going down slightly before increasing revs. And, I had one occurrence of the engine stalling when suddenly stopping the car. My best guess is a torque converter lockup problem. Can a reflash at the dealer help with this?


Car has about 128,000 miles with trans fluid changed (ZF Lifeguard) at around 100K miles.

 

Could easily be a minor engine issue that in turn affects the trans so start by checking what you can via OBD live data, especially fuel trims.

Also check the battery under heavy load does not let the volts sag.

You may want to re-check the trans fluid level in case some has seeped out.

 

I thought my 2003 Base S-type was succumbing to 'the lurch' but an observant AAMCO tech noticed the torque as I revved the motor while holding the brake... MOTOR MOUNTS!
(the action was just enough to momentarily separate the air intake)

 

Fluid level was low. I was able 3/4 quart before I ran out. Shifts better now. Will order more fluid and check again at next oil change.

 

Fingers crossed!

 

put in a bottle of Lubegard Platinum it does work.