Ok, I realize that the manual says to run 80-90w, but. . . years ago the head mechanic at what was at the time my local Toyota garage told me they always added either a pint or half a pint of ATF to the transmission when they filled it up either new or when doing a fluid change, to make it shift better when cold. I did it to a couple of trucks with good results. But it has been fifteen years since I've done it. Doing a fluid change in my 89 and was going to do the same to it (and it is noticeably stiffer to shift cold) Only problem is I can't remember whether to add a half pint or a pint.

Anybody else heard of this or done this? How much ATF did you add?

 

Some manual trannys spec ATF. The Ford Escorts I run do. Ford specd straight 50 weight motor oil for their heavy duty New Process trannys in the 1970s.

Unless your service is very high temp, extreme duty, you could probably run pure ATF if you wanted to.