Can I Mix Type F Tranny Fluid With Dex/Merc in a 57 T-Bird Auto Transmission?

[Tim Shea]

I had some work done on my new to me 57 a couple months ago, which included work that required the automatic transmission to be drained. I am pretty new to owning a 57 T-Bird, and having a 50's era automatic transmission, so I am a novice on some related things. The repair tech said that "transmission had been worked on" so Dex/Merc transmission fluid would be appropriate, and that is what they used. Previously, I had bought a couple of containers of type F transmission fluid to have on hand. Today, I noticed the transmission to be a little low. Can I add/mix type F with Dex/Merc, or am I just asking to problems in the future. Hate to just waste the Type F, but I surely I not want to screw up the transmission over a couple of containers of fluid.

[Bloo]

I would use only what the rebuilder recommended. In 1957, Type F did not exist yet, Type A was used. Dex/Merc older versions (2, 3, maybe others) are the successor to Type A.

 

In 1963 (IIRC) Ford introduced their own fluid type, and recommended using it retroactively all the way back to their earliest automatic. I have seen at least one case where that did not work out well at all and the transmission had to be changed back (to Dex II or III as a Type A substitute).

 

While I doubt a little mixed in would make any difference, I wouldn't use it. I found these transmissions temperamental at best. If it works right, don't change anything.