Zinc Additive in ATF? (for use in Manual Trans)

[FusilliJerry82]

I remember reading in a thread about either Redline or Lucas zinc additive (I can't find it), and one person suggested it be used in differentials and manual transmissions for silky smooth shifts or something to that effect. It was toward the end of the thread and no one addressed the post.

So I'm gonna change the fluid out in my dad's stick shift 91 F-150 (M5OD) soon, and that came to mind. Is there something to that? This transmission uses Dex III ATF, and as far as I know, ATF has little zinc to speak of. ATF is used in the M50D, for those who don't know, as the design is such that a gear oil or MTF from say Redline is too thick for sufficient splash lubrication.

So, what do you folks think? I already have the Lucas additive, so should I add some to the tranny? I'm also gonna be doing the diff and transfer case sooner or later, how about those?

 

[unDummy]

10cst MTF's/MTL's will shear a couple points in usage. So, that rumor of it not being sufficient for splash lubrication is [censored]. And, a full synthetic 2cst thicker MTL will flow pretty well or equivalently to a thinner mineral ATF when the temp drops. 18000cst @-40c for typical mineral DexronIII and 12000cst@-40c for Redline MTL.
All those manuals using mineral ATF would've self destructed during 1 Canadian winter if that "flow" "splash" lubrication theory were true.

If you want Zinc, fill it with latest Hondacura MTF.

 

[mechtech2]

What makes some parts move and be slick will not engage synchros for good shifting.
By all means, lose the ATF and get a light or medium dedicated manual trans lube.
Red Line MTL or Amsoil MTF are top contenders, and are superb.
A little thicker than ATF, but so what? It's a good thing.

 

[PandaBear]

If you want Zinc in ATF Honda's Z1 is the one to use. It has loads of ZDDP in it already due to its manual like design.