Hello,

I am the new owner of a 1967 Valiant with a 225 slant 6, and a 904 automatic transmission. I bought it on ebay last week and drove it home from Ohio to Spartanburg, SC. It ran like a champ, and got over 20 MPG.

A couple of days ago, I checked the transmission fluid level, and it looked a little low. About 1/2 way between the full and "add one pint" mark. I added some ATF +3 fluid. Guy at Advance Auto looked up my car in his computer and it showed this as the one to use.

Well, I emailed the guy who sold me the car, and he said he always used Dexron III.

Is there a problem with mixing these two types? I searched the forum a little and saw that mixing type F with Dexron is a big mistake (makes a gelatinous goo), but can't find any mention of +3 and Dexron.

Anyone else in Upstate South Carolina? I just found this website and am thankful for it!! I'm already learning a lot just by reading about other's problems/questions.

Thanks,
Jon

Dexron and ATF+3 mix just fine and won't cause problems. The parts store guy and his computer are full of it, though. Dexron is the correct fluid for that transmission. ATF+4 is better, but ATF+3 is not.

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Too many people who were born on third base actually believe they've hit a triple.

No you shouldnat have any problem. But I prefer to use type f trans fluid. It gives firmer shifts.It seems to really help a worn 904 or 727's performance.
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Medium-popular trick occasionally hyped by the usual suspects on the magazine rack, but it's not good for the transmission.

Type-A/Suffix-A, the original fluid spec through 1967, was replaced by Dexron throughout the auto industry in the late 1960s, and Dexron has been evolving ever since. Type-F was a Ford fluid of the late 60s through mid '70s, used in combination with specific clutch materials Ford was using in their transmissions at the time. It is an archaic and thoroughly outdated fluid. Compared to Dexron, Mercon or Chrysler ATF+4, the Type-F has very poor lubricity, very poor resistance to oxidation, very poor extreme-pressure properties, very poor viscosity stability at cold and hot temperatures, very poor detergent action. It's a friction-unmodified fluid, which attracts drag racers to it because it causes harder shifts. That is its only claim to "fame".

Others, as you have seen in this thread, use Type-F because for one reason or another they prefer harder shifts. The Torqueflite is well enough engineered and built to be resistant to abuse, but I don't see any point in deliberately using an inferior fluid. There are less abusive ways of hardening the shifts if that is something you regard as desireable. It is common to hear or read that harder shifts are better for the life of the transmission, but that's not necessarily so; it's an oversimplification.

Off-the-shelf Dexron is your easiest, least costly choice, and it is a safe one. The latest Chrysler Mopar ATF+4 is better than the current Dexron in terms of virtually all the important performance characteristics, but ATF+4 is expensive. ATF+3 isn't as good as Dexron.

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Too many people who were born on third base actually believe they've hit a triple.

Just dont tell any of my transmissions and Ill be ok. LOL
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The friction material type F was formulated for was one made with asbestos. Even Ford has not used this fluid for years. Dan is right about firming up the shifts in another way. I think most street cars only need a heavy duty type of shift kit though, not the chirping street/strip kit that is so popular. Slamming shifts ends up hurting hard parts in the transmission and the rear end. In a racer you upgrade hard parts or live with the breakage. It is not true that mixing type F and dexron makes goo. You can mix any of the conventional ATF's and any of them will work in any trans, it's just not best and won't perform as well or last as long as it should.

Sure he is absolutely right. But I have built enough transmissions and used type f in enough of them to know that it will not cause catastrophic failure on its own.

as for slamming shifts some of your shift kits accomplish this by trying to engage the next gear to soon or hold the one you are in to long.
there is a company called transgo that makes the finest shift kits for torqueflites. Well engineered to improve shifting and transmission life not just squeal tires when you shift.



Also type f is thicker. It helps to raise pressures on a worn trannsmission just like some of the wonder additives to keep you going a little longer.
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Sadly they dont' make 'em for the lockup 727's that I can find

Im not positive but you can always ditch the lockup trans. there are lots of older non lockup units available.
I was never a fan of a lockup TC in a performance car.
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Last I checked, kits for 727's, 518's, 46RH/46RE's are the same, and most 518's are lockups, and most if not all 46RH/RE's are lockups.

Hm.. I was just looking for one that was listed as compatibale w/ an '82 727 and couldn't find one. Didn't think about interchange with the newer ones.

Nope shift kits are different as valve bodies are different.
I believe there are some made but the 904 one i have laying here says non lockup on the package.
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I have to vote for transgo as well. The are the only kits I use anymore. Hughes and ATI make some nice heavy duty parts and are reasonable too. I would stay away from that other brand, whats it called, B&S?

you can do worse then mixing those fluids. once I filled an CVPI trans with hyd. fluid because someone at work put it in the container marked ATF. I had to pull the pan again change the filter and gasket and the quart or so of ATF I already put in the vehicle. that was anoying.

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64' Valiant Signet 5.9, 64' Dart 170 moredoor 3.7, 67' A100 3.7, 00' Dakota SLT 4.7