hi--

i'm looking to swap automatic transmissions from a 1979 300sd parts car into a 1980 300d. any known issues or problems?

current status:
parts car, 1979 300sd: transmission out of car, torque converter still in car (seized engine due to broken timing chain, ouch)

destination car, 1980 300d: transmission is slipping


any help greatly appreciated!
thank you all!
-noah

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1980 300D (non-turbo, 421k miles)
1984 300TD (turbo, 305k miles)
1985 Vanagon (170k miles)