Mopar sent the 4 speed cars out from the factory with both gear oil,80-90 wt. and ATF The deciding factor was where the cars where being sent to be sold, if it was to a dealer who lived in cold country it got ATF, if not cold country they got gear oil. I went to several of the old Mopar drag seminars, they always recommended using ATF in the NP 833 regardless if drag race only or road racing I've used ATF in all my 833 since 1976