I don't see why it would hurt to replace that old transmission fluid. You might be surprised by the difference.

I just put in Synthetic ATF and am now enjoying a smooth shifting 300CD.... however now I have a VERY BAD clunk from the rear end..whatever... if it doesn't end I might trade this thing in for a Corolla..

Just get an AT Filter Kit (it comes with all the washers to replace the old ones)

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2008 BMW 335i Coupe