transmission fluids - critical differences? 1

[knowlittle]

I am reading Lubrication Engineers Manual by AIST. Goal: to be a certified lube engineer. But as far as transmission fluids are concerned, I am as ignorant as an average driver. So here is my question. Is it a big deal to use Mercon V on late Fords and Dexron VI on late Chevys? Exactly what can happen when I use Dexron on Ford, and Mercon on Chevy? Will it ruin the transmission? Or just some performance loss? Is Multi Vehicle ATF really what the label claims? If someone can give me a ATF fluid primer and a link for further technical reading, I will greatly appreciate. Thanks.

 

[romke]

ATF's are quite complicated products that especially differ in frictional characteristics, low temperature viscosity and oxidation stability. over the years we have seen considerable improvements both in cold weather operability, drain intervals and wear protection.

most modern varieties (Mercon, Dexron and the special products approved or various Aisin and ZF transmissions mounted on various makes of vehicle)) can be mixed - without immediate damage as a result. In the long term it however may have an adverse effect on shift quality and may also lead to higher wear.

the general rule therefore is to stick to the original recommendation.

for older Ford and Borg-Warner transmissions that required a Ford type F fluid (i am talking about the pre-Mercon era now), mixing up the Ford and GM-type like fluids should be avoided at all times, since severe shift problems will arise quickly and a lot of damage to frictional elements can be the result.

Since the nineties frictional characteristics are more alike between the various transmission builders, so adding a quart of the "wrong" oil to a low oil level transmission is not that critical anymore, read: does not cause immediate damage.

The various products on the market now differ more in oxidation stability (oil change interval) and to some extend in anti-wear quality.

some useul info can be found here:

http://www.i-car.com/pdf/advantage/online/2007/062507_ATF.pdf

 

[rmw]

Am I wrong about this? The F in Ford type F stands for 'fiber'? Did this ATF have a fiber additive or did I just come up with that in a dream (nightmare)?

If I am right, obviously a transmission not designed for the ATF to have fiber in it is in trouble.

rmw

 

[romke]

as far as I can remember type F only indicated that the fluid was designed for Ford USA automatic transmissions. Details where laid down in various Ford specs like M2C33F.

type F developed into a general term for this type of fluid as opposed to "type G" (for GM and most other manufacturers) - the difference being mostly in the frictional characteristics - and those had a direct relation to the frictional materials involved.

all passenger car autotransmissions do use some kind of fiber on their frictional materials because these make it possible to improve shift quality/comfort. in applications where durability is more of a concern non-fiber based frictional materials are used, eg construction esuipment.

 

[knowlittle]

Thanks. I also read the linked presentation material.

 

[Metalguy]

Type F ATF has higher friction, especially at low slippage speeds than Dexron, and Ford clutch packs rely on that factor. Use of Dexron delays clutch lockup, which promotes wear and slower shifts.

Many people with GM transmissions who do not like the slow shifting/high slippage characteristics of Dexron simply switch to type F. I personally have run many GM trans. on type F for many thousands of miles and never had a clutch problem.

Gold is for the mistress - silver for the maid
Copper for the craftsman cunning in his trade.
"Good!" said the Baron, sitting in his hall
But iron - cold iron is the master of them all.
Rudyard Kipling

 

[drwebb]

Type F is a pretty mild 'spec' and will also have different (less severe) low T performance/capability and oxidation stability/durability than Mercon types as well as different friction/shift feel. Actually not a spec but more of a type now as I don't think FOMOCO maintains the spec anymore, so any blender can claim almost anything is the type. Same is true of Dexron III types.

Dexron/Mercon specs were fairly similar- mainly differing in the test choices the OEMs required to demonstrate performance(e.g. Dexron gauges oxidation from the transmission cycler test while Mercon specs passing the ABOT bench test)- so the same fluid could be formulated to meet both and most were marketed this way. Not so Dex/F or Merc/F.