# Type F fluid in TH400



## 1968gto421 (Mar 28, 2014)

Back in the '60's and '70's I helped my brother race his Olds 442's (he had several in that period), all had TH400's as he wanted more consistency than a 4 speed.
He changed the fluid and filters religiously and always refilled the TH400's with Ford Type F fluid. He and his buddy's claimed the Type F reduced slippage and gave quicker, firmer shifts. I do not recall any of those guys having trans problems.
I'm about to do a fluid and filter change on my "68 GTO's TH400 and am seriously thinking of replacing the fluid with Type F. Is this still a viable thing to do or have kits like Transgo eliminated the need to go to Type F for reduced slippage and firmer shifts??  I've looked at instructions for the Transgo and it sounds like it's best to install it when the trans is being rebuilt (which mine is far from needing right now).
Unless there is a good reason not to go with Type F, I think it would be an improvement in shifts, etc., until the Th400 needs a performance rebuild.
Thanks, all!


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## 67Twistytee (Feb 24, 2014)

Type F is fine but it's no longer spec for todays cars and getting harder to find. A good quality Dexron III is great for a street driven TH400 and easier/cheaper to locate.


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## geeteeohguy (Feb 2, 2008)

Type F had different friction modifiers than Dexron back in those days, when whale oil was still used in both types. Things have changed, and any Dexron or Mercon fluid will be fine. In my opinion, the 'firmer shift' thing was more home-spun hopefulness than anything else. Line pressure and valve body programming control shift pressure....not what type of fluid, as long as the viscosity is the same.


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## 1968gto421 (Mar 28, 2014)

Thanks, guys, that clarifies it for me. Will go with the Dexron/Mercron as it is readily available (cheaper) and has to be much better than what is currently in my TH400. Will look into a Transgo shift kit later as they have a video of in-car installation.


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## Lemans guy (Oct 14, 2014)

*Trans Fluid*

421, good advice there. I just went through this putting a rebuilt trans in, TH350. I agree not to use the type F, works as the Hydraulic in fluid in my tractor, which was built in 2010 and designed for a certain fluid and the manufacturer recommends type F, different speeds , different purposes.

The dextron family is the way to go and my research showed that the latest version Dexron VI I think, was the best. Why? Well the petroleum engineers and the trans engineers modify their mixtures to reduce foaming and work cooler and resist heat, resist breakdown etc. Each new number III or IV and so on has some little improvements that will be factored in against the things that hurt trannies. 

Why would they do that?....?...............:smilielol5:Money

The don't want warranty work on trannnies and they want it to work as designed. I read somewhere the particular difference between III and VI and as I recall six was much better. So unless your car/tractor requires it, and it doesn't, 

your TH400 can benefit from 45 years of engineering without hurting originality and helping reduce friction, resist heat, not breakdown as fast, resist foaming etc etc.....:willy:

3 will work, so will 4,5, and 6.....but they sell 6 at the local parts store and read the back it can be used in any car requiring the prior dextron blends,.....

Not F... I think Ford required that back in the day and as GEETEEOH said had no friction modifiers and the Shift Myth was born!:bannana::bannana:

Go with the engineers, forget the myths, and the latest engineering, and the latest at least on dextron trans fluid.is six....maybe 7 soon...:cheers


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