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Still, in a Volvo manual trans, Mercon and Dextron are not useable. The frictional qualities as they approach lock up are determined by the length, quantity of and the affinity of the chains for each other (They like to stick together and not separate)of the polymner chains that comprise the fluid.
The longer the chains and more of the longer chains the more of them that like each other the higher the resistance to squeeze out. One problem is that these are the more difficult to pump as the chains do not like to separate as they pass through the pump. If the clearances between mating parts are close together the greater the pressure needed to push the fluid.
Ford Automatic trans that use the Type F are loose tolerance units, with lower pressures than the GM and high performance Ford trans which used very tight clearances and higher pressures.
Dextron and Mercon have proprotionately, fewer of the longer self liking chains than Type F. That is why Dextron feels and pours differently than Type F. Like sugar water and molasses. They taste similar but are different.
You have forgot one item of difference between a manual trans and automatic trans that dictates which fluid to use.
The PUMP. If you have a fluid that does not like to cling and allows it self to be squeezed out as Dextron does, you compensate by putting the fluid under pressure. Like the oil in the motor, it is under constant pressure, even the synthetics, to prevent such squeeze out. Last I looked, the manual trans is lubed by fluid clinging to and getting carried from one gear to another. No pump that I am aware of for the gears.
I will grant you that any Ford auto trans that has been rebuilt with newer parts that have closer tolerances and fit, can use the Dextron. That trans has a pump. Rebuild a manual trans to the same increase in tolerances and fill it with Dextron in my opinion will create a friction heater directly under the shift lever that will burn itself up in 10 to 20 thousand miles. Fill it with Type F after the same rebuild and the same will occur. The Type F will not be able to get to the places it needs to lube since it cannot fit.
Duane
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