I'm doing a complete drain and refill on my manual 3 speed.(A-390)Did Mopar, (in 1979 pickup trucks) use a red colored 90W gear oil in this or any other application for Mopar manual transmissions? If it's red gear oil, it will "stink" like gear oil or it will smell like trans. fluid? Correct?

If it's gear oil it'll have that nasty musty smell like you just cracked open a 40 year old diff that never had an oil change and it'll drool like syrup...if it's red and runny it may be ATF (which was common to use per the factory manual in manual trannies too...). Hopefully it's not a combination of the two or???

When in doubt drain it, and replace with some good quality gear oil or ATF depending on your preference.

-D.Idiot

The Factory Used atf in the manual 3's and 4's For years.

It's probably atf.

I usually Refill Mine with 10w-30, Although atf will give you slightly more RWHP / Gas Mileage - and we're splittin hairs with that.

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