ATF or MTF, Dexron III is what i've aleways used.
Check the filler plug first and then drain.
Be carefull as the oil flies out sideways by quite a distance.
5 Litres of ATF Dexron 3 / III Transmission Oil. General Motors Dexron III. General Motors Dexron IIE. Semi-Synthetic ATF. This allows this high performance fluid to maintain a long transmission system life and also to be used in more severe conditions of service.
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