1984 Mercedes 500 SEC delayed upshifts
The owner reports delayed upshifts despite fluid top-ups and later fluid-and-filter service. Replies offer separate checks, but no confirmed cause or repair outcome is reported.
The fluid service did not resolve the complaint
jonnyoutram identifies the car as a 1984 500 SEC and describes intermittent failure to shift up. A slow leak had previously required transmission-fluid top-ups, but the symptom later continued even when topped up. The owner then says the fluid and filter had just been serviced, yet the transmission seemed to hold in first or second gear. A rebuild from a few years earlier is mentioned as something the owner had been told; its scope is unconfirmed.
The kickdown button seemed to work
After a member suggested the kickdown switch, jonnyoutram said he had checked the button and it seemed to work. He asked what to check next. The thread contains no later confirmation from him of the failed component or a successful repair.
A separate 420SEL kickdown-switch experience
JayKinFL described a different car, a 1991 420SEL, whose carpet held the kickdown switch down. He said the shifting trouble stopped after the switch popped back up. That result belongs to his car; it does not establish the cause of the 500 SEC complaint.
Members separate several possible shift-control checks
BENZITCH asks whether the shifts are mostly late and suggests checking transmission shifter bushings and the modulator. C32AMG/02 distinguishes the modulator’s effect on shift feel from the Bowden or TV cable’s effect on shift timing, and also raises sticking valve-body valves as a possibility. Television adds vacuum lines at the transmission and near the engine as another possible source of poor or hard shifts. These are contributor suggestions, not a diagnosis of this car.
Source reply ↗ · BENZITCH
Source reply ↗ · C32AMG/02
Source reply ↗ · Television