Last year a friend had a 240 kompressor which the rad is known to mixup water and tranny fluid. He noticed and topped up his antifreeze for around a year then one day his transmission started slipping. He replace the radiator and we flushed 20 liters of fresh fluid through it. Worked great for 3 days upon removal of the pan chunks of friction material was found. I believe the friction material swells with water/ antifreeze.

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92 e300d2.5t
01 e320
05 cdi
85 chev c10