Are dino 80W-90 and trans fluid compatible ?

[junebug]

I have a stock 1979 Dodge pickup 225 slant six with a 3 speed manual trans. It could use either 80W-90 gear oil or Dex.III trans fluid in the transmission.Which one,or perhaps a blend of the two?

 

[Pablo]

Quote:

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I have a stock 1979 Dodge pickup 225 slant six with a 3 speed manual trans. It could use either 80W-90 gear oil or Dex.III trans fluid in the transmission.Which one,or perhaps a blend of the two?

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Will they mix? Sure. Is it ideal? No. The two fluids are very different. In your climate, if the ATF produces OK shifts I would stick with Dex III.

Years ago I drove a stick with ATF/gear oil mix. Worked fine. So beyond doing a detailed study.....I suspect most answers will be.....opinions.

 

[Tempest]

I would go with a Syncromesh weight fluid such as Amsoil MTF (make sure that you use a site sponsor) which is sorta in the middle of the two and has a strong additive package.