1997 E420 Transmission Shift Quality Deterioration

[jgl1]

1997 E420, 56K miles, manufactured 3rd quarter 1996. Equipped with 722.6 electronic transmission - fluid and filter renewed 18 months ago at 50K miles, using M-B parts.

Over past couple of weeks, the transmission's shift quality has started to deteriorate.... to the point that the 2-3 and 3-4 shifts are now rather drawn out and accompanied by an almost head-jerking completion of the shift. Shift quality can be tempered somewhat by modulation of the accelerator pedal.

Prior to this, shifting has been asymptomatic and the transmission has required no service since new, other than fluid renewal.

Quick inspection reveals proper fluid level, with no evidence of leaks.

Any ideas? Control unit failing? Or is this one of the early 722.6s that will require an overhaul?

Were there software upgrades required for these early W210 electronic transmissions?