I put Ford Type F transmission fluid into my Chrysler. Can I leave it in or should I drain it?

Dear Car Talk

Dear Car Talk | Jan 01, 1997

Dear Tom and Ray:

I was startled when I checked the transmission-fluid level on my 1967 Chrysler New Yorker and found it about three pints low. I then looked under the car and saw that the area between the engine and transmission was a bit wet with fluid. Immediately, I went to the discount store and bought a bottle of trans sealer and conditioner and some automatic transmission fluid to bring up the level until I could fix the leak.

Due to the confusing array of brands on the shelves, I accidentally picked up three bottles of Ford Type F fluid, instead of the Dexron that my Chrysler calls for. I didn't realize my mistake until I had already poured the stuff in and driven the car. Is there any real difference between Ford Type F and Dexron? Is this fluid going to loosen my tranny's teeth and cause them to fall out? -- John

TOM: Probably not, but I'd drain it anyway. There are four basic types of transmission fluids, and three of them would have worked fine in your car. But in "Wheel of Fortune" terms, you spun "Lose a Turn," John.

RAY: If you put Dexron, Mercon or Chrysler 7176 transmission fluid in just about any transmission, it will perform just fine. That's because all of those are what are called "friction modified" products. That means, in layman's terms, they are extra slippery.

TOM: Ford Type F, on the other hand, is not friction modified. And in transmissions that are not designed for it, Type F fluid will cause rough shifts, and can even cause damage by making the torque converter engage before it should.

RAY: In the early days of automatic transmissions, the engineers at Ford thought people who bought automatics would WANT to feel the shifts taking place. So they created this less-slippery fluid to make the shifts jerkier an. d more apparent to the driver.

TOM: GM, in its better judgment, decided that if people were buying automatic transmissions, it was because they didn't want anything to do with shifting, and didn't want to know anything about it. So they came out with Dexron, which was a slipperier fluid that masked the shifts very nicely.

RAY: Before long, Ford realized that GM was right about what the customer wanted, and they came out with Mercon, which is also a "friction modified" fluid.

TOM: And the reason you're not noticing any problems yet in your car is because you only added three pints of Type F to a system that holds about 20 pints. But it's not good for the car, so drain it out and put the right stuff in it.

RAY: And next time you go to the discount store, pay more attention to the labels on the products you're buying, and less attention to the mannequins wearing string bikinis, OK, John?

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