The tranny in the 240 is pretty bullet proof. How many miles on it?
Mine had 330 and is still going. Vacuum lines first and new modulator valve certainly before a tranny . You might just replace the tranny and have the same problem because you didn't do the vacuum stuff first

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Ricali

03 C240 4matic wagon
95 300E 234,000
7 prior 240;s 5 still going
81 300sd gone
65 230sl gone
49 Studebaker Champion
90BMW convert.167,000
60 Dodge D-100