Type "F" ATF

[MolaKule]

Ok, back to the original reason for this Forum - Lubricant Education:

Other Thread With References:

Today, Automatic Transmission Fluid (ATF) is a specialized hydraulic fluid with friction modifiers to ensure the proper static and dynamic coefficients of friction during engagement/disengagement.

Ford Type "F" ATF is a fluid with very low levels of friction modification.

Ford Type "F" ATF is often used in racing transmissions such as the PowerGlide and TH400 Turbohydramatics because of the positive lockup, IE, little to no slip in the clutch packs during engagement.

Question:

Why did Ford ever use an ATF with an extremely low level of friction modification?

 

[Olas]

Because it works effectively where a positive lock-up is required?

I dont know if this is a genuine question or a test coming from you!

 

[GSCJR]

So, would it be safe to assume that if the shift feel was not too harsh the clutches would last longer as a result?

 

[Shannow]

Different clutch application rates to the GM theory ???

e.g. Did Ford use slower clutch application to slur the shfts rather than FMs ?

 

[MolaKule]

Originally Posted By: Olas


...I dont know if this is a genuine question or a test coming from you! ...


This is a Q&A forum whose original purpose was to do Q&A for educational purposes.

 

[UNC017]

You know, I've always KNOWN that this was the difference, and that Ford chose it specifically... but I've honestly never known why.

My ASSumptions are that several factors came into play.

1) In the early days, friction modifiers were probably a bit of a dark art, and Ford chose a minimalist approach, tailoring their clutch apply rates to work with an easy-to-produce fluid.

2) Ford considered the fact that god-knows-what oil might be mixed with ATF in the field and chose to design their transmission to be relatively independent of FM package. After all, some of the first semi-automatics that people had become familiar with simply used engine oil.

 

[Shannow]

Originally Posted By: MolaKule
Originally Posted By: Olas


...I dont know if this is a genuine question or a test coming from you! ...


This is a Q&A forum whose original purpose was to do Q&A for educational purposes.



And I for on appreciate it being used for that Molakule

 

[tinmanSC]

Originally Posted By: Shannow
Originally Posted By: MolaKule
Originally Posted By: Olas


...I dont know if this is a genuine question or a test coming from you! ...


This is a Q&A forum whose original purpose was to do Q&A for educational purposes.



And I for on appreciate it being used for that Molakule

I for on appreciate it too.

 

[MolaKule]

The article below, Page 14, give some history of early Ford fluids:

Ford ATFs

The answer lies in the design of the early Ford transmissions.

 

[UNC017]

So reading both on and between the lines:

Ford used a type A FM fluid initially.

When "lifetime fill" became an objective, Ford didn't believe they could achieve it with the Type A fluid and moved to a non-FM fluid.

The between the lines part: the type A was life-limited because of the friction modifiers?

If so, that kinda goes with my ASSumptions earlier. The early Ford transmissions were designed to not count on the fluid maintaining its characteristics to the same degree that GM and Chrysler did.

 

[MolaKule]

Originally Posted By: Shannow
Different clutch application rates to the GM theory ???

e.g. Did Ford use slower clutch application to slur the shfts rather than FMs ?


Shannow is converging on the answer.

Consider this: The size of the clutch packs do matter.

GM wanted softer shifts which meant relatively longer clutch engagement times. GM had larger diameter clutch packs which meant larger clutch pack masses which meant they could dissipate more heat.

Since Ford had ______________, they had to insure that the __________ were _____________.

Hence a fluid with the Type F Mu/V slope characteristics had to be used, IE, its static coefficient was higher than the dynamic coefficient.


Hope that helps.

 

[MolaKule]

From an older thread:


Quote:
The friction coefficient of Dexron III/Mercon fluid increases as the sliding speed increases. The friction coefficient of Ford Type F fluid decreases as the sliding speed increases.

Stating the above sentence another way, Ford Type F fluid has a Low Cf at high speeds, and a high Cf at low speeds. Conversely, Dexron Type fluids have a High Cf at high speeds and a Low Cf at low speeds.

 

[RobtE]

Originally Posted By: MolaKule
GM wanted softer shifts which meant relatively longer clutch engagement times. GM had larger diameter clutch packs which meant larger clutch pack masses which meant they could dissipate more heat.


So, GM bought "softness" with slippage. Slippage means inefficiency, inefficiency means heat, and heat requires large diameter clutch pack mass to withstand it.

Ford opted for small clutch packs, which meant that the clutch pack mass was insufficient to withstand the sort of heat the GM Hydramatic could handle, and required less slip on clutch engagement to minimize heat.

 

[MolaKule]

RobtE wins the Piston Cup Lapel Pin.

Ford had smaller diameter clutch packs in some of the earlier transmissions so they had to use a quick lockup fluid to keep localized heating and wear to a minimum.

A number of factors determine clutch heating: effective clutch surface area (determined by clutch diameter and number of clutch discs/plates), engagement time, applied torque, and actuation pressure.

These Ford transmissions had sufficient actuation pressure and short engagement times, but the effective clutch surface area was relatively smaller than GM and Chrysler transmissions of the same era.

Ford Type F is still used in modified racing transmissions such as the GM PowerGlide and TH400 where you need a quick lockup.