If the fluid is dark as described, it is bad news. Most probably the seals have given way causing the problem and if engine oil had been filled in, that would definitely cause transmission failure.
Drain the fluid and check for debris coming out with the oil. Put a strainer while draining and you should be able to see debris if any is present, meaning you would need to rebuild or replace the transmission.
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Wednesday, July 31st, 2013 AT 5:13 AM