My parents have a '67 Mustang, and we need to plunk in more transmission fluid… we belive that type F should go in, but we’re not quite 100% certain as to what type of fluid is already in there (Dextron/Mercon or Type F). From the research I’ve done, everyone says ‘don’t mix the two types!’, but I have yet to find something that tells me what happens if you do mix them. So, obviously, here’s the question: what the heck happens if you mix the two types together? Would it matter which one was in the transmission first, or would it be a moot point? Also… how can you tell if they’ve been mixed together? Will the transmission start acting like it’s been taken over by hostile spirits? Any links to coherent information on what happens woiuld be greatly welcomed!
It’s not the mixing that’s the problem, it’s having too much of the wrong stuff in the transmission.
Different automatic transmission fluids have different friction characteristics that affect the shifting. The wrong fluid can cause grabby, jerky shifts or mushy, slippy shifts.
In your case, you can’t go wrong using type F. I don’t know if one of the Dexron/Mercon fluids is also suitable, but I wouldn’t be surprised if it is.
Hondas and later model Chrysler Corp. products seem to be the most sensitive to needing the prescribed fluid to work properly. On any car, I wouldn’t worry about a quart or two of the wrong fluid for an emergency top-up, but I wouldn’t want most of the fluid to be the wrong stuff.
For older Ford automatics and certain imports, Type “F” is usually required. Most Fords since the 1980s require “Mercon” fluid, which is Ford’s equivalent of Dexron II.
For General Motors, Chrysler and other imports, Dexron II is usually specified.
NOTE: Some newer vehicles with electronically-controlled transmissions require Dexron IIe or Dexron III fluid. GM says its new long-life Dexron III fluid can be substituted for Dexron II in older vehicle applications.
CAUTION: Using the wrong type of fluid can affect the way the transmission shifts and feels. Using Type F fluid in an application that calls for Dexron II may make the transmission shift too harshly. Using Dexron II in a transmission that requires Type F may allow the transmission to slip under heavy load, which can accelerate clutch wear.
I’m assuming that you have an automatic trans. Newer stick shift transmissions also use Dextron ATF. If your Mustang has an automatic, use Type F. If you use Dextron, it will probably ruin the internal seals and you’ll be rebuilding it soon. Same way with brake fluid on Jags and other euro cars, they use mineral oil brake fluid and putting DOT4 fluid in there will ruin the seals. Don’t ask me how I know this…
Considering this transmission (the 'Stang is auto, 289 engine, pretty much stock) has well over 200K miles on it… I think a rebuild is in its future no matter what. (Or it may be better/cheaper just to plunk in a new transmission.)
Oh dear. I take it you learned that the hard way, BillWelter? Ouch! (My SO has a Jag, as an aside.)
Well, we’re taking the 'Stang in for a full power flush on the transmission this weekend to make sure that Type F and only Type F is in there. If the tranny is all right, this will just (hopefully) make it last longer. If the tranny is shot… this will make it painfully apparent pretty dang quick, I think.
(Or it may be better/cheaper just to plunk in a new transmission.)