An acquaintance has a 1988 190D. Mileage is unknown....odo broke at 200k.

He finds that SOMETIMES the tranny will not shift into 4th. When this happens, he stops the car (i.e. turns it off), turns it on and drives and then it ALWAYS goes into 4th and is able to do so for the remainder of the trip. He has recently changed the fluid and filter. His conclusion is that the tranny is on its way out.

My question: what, other than a bad tranny, could account for this symptom (vacuum stuff, etc.)? It's 722.414 transmission.

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14 E250 Bluetec "Sinclair", Palladium Silver on Black, 153k miles
06 E320 CDI "Rutherford", Black on Tan, 171k mi, Stage 1 tune, tuned TCU
91 300D "Otis", Smoke Silver, 142k mi, wastegate conversion

19 Honda CR-V EX 61k mi
Fourteen other MB's owned and sold
1961 Very Tolerant Wife

My first guess is that the kickdown switch is full of dirt. It's located under the accelerator pedal, you probably will need to remove the mat to get to it. If it shorts, it holds the transmission one gear too low. Clean or replace and see if that does it.