The brief
The E250's owner found a puddle of reddish fluid under the parked car, the unmistakable sign of a transmission fluid leak. He brought it in, which is the right call, a leaking gearbox loses fluid, and a gearbox running low overheats and damages itself. The trail pointed at the transmission pan. The pan bolts to the bottom of the gearbox and holds the fluid that does the lubricating, cooling and hydraulic work, and on these the filter is built into the pan. The pan seals with a gasket, and over the years heat cycles harden it so fluid weeps out the seam, runs down the pan, and drips into a puddle. A leaking pan gasket doesn't reseal, and the filter wants doing with it, so it needed a complete pan-and-filter replacement, a fresh fill, and the level set properly.
The diagnosis
With the gearbox cleaned off, the leak traced to the transmission pan, fluid weeping from the gasket seam, not from a line or a seal higher up. The gearbox itself was shifting fine, no slipping, no fault codes, it was purely the pan leaking. That's a pan-and-filter replacement with a fresh gasket, refilled with the exact Mercedes-spec fluid and the level set at temperature.
The work
The old transmission fluid was drained, the pan dropped and the pan-and-filter assembly replaced with a new genuine Mercedes unit and a fresh gasket, the magnets cleaned off and both faces cleaned up. The gearbox was refilled with the exact Mercedes-spec fluid, then brought up to the specified temperature and the level set precisely the way the procedure calls for, with the fill plug torqued to spec, and the adaptations reset. A road test confirmed clean, crisp shifts through the range, no flare, and the pan dry.
The outcome
No more transmission fluid under the car, the pan sealed and dry, crisp shifts, and the gearbox running on fresh fluid at the right level. The E250 went home with the leak resolved. A leaking pan only worsens and quietly drops the fluid the gearbox depends on, so replacing the pan-and-filter assembly, refilling and setting the level right stopped the leak and refreshed the gearbox in one job.
