Kasper wrote:
> My question is: Could using the wrong fluid have caused the clutches to
> burn out so quickly? I donąt see any other explanation. Wouldnąt this
be
> considered negligence or incompetence on the part of the people who used
the
> wrong fluid?
It's possible. Dexron would most likely only directly damage the torque
convertor clutch, but when the TC clutch lets go it sends fluff all
through the rest of the transmission and that could have blocked the
filter and caused low pressure, which could have then burned out the
rest of the clutches.
But that's just a hypothesis, it could have been any number of things.
>
> Also: What is it about Dexron that causes damage to Chrysler
transmissions?
It has the wrong differential between its static and dynamic coefficient
of friction. In other words, a clutch lubricated with Dexron III will
slip easily, but then grab when it stops slipping. ATF +4 has a much
smoother transition between sliding and sticking because the static
(stuck) coefficient of friction is much closer to the dynamic (slipping)
coefficient of friction. The torque convertor clutch in Chrysler
electronic automatics (and now virtually all other manufacturers, but
Chrysler was the first to use this system in 1989) is designed to be
used in a partial-lock mode, where its engaged but deliberately
slipping. This is done in 2nd, 3rd, and 4th gears (now 5th and 6th too
on newer transmissions) to improve fuel efficiency by reducing fluid
coupling the losses in the convertor at the high end of each gear. But
when the clutch is being deliberately slipped like that, Dexron III
fluid will cause it to "grab" over and over causing a noticeable
shudder. That will also begin to break the friction material off the TC
clutch, and then it contaminates everything else or plugs the filter.
When the filter plugs, fluid pressure drops and the servos can't keep
the other clutches firmly enough engaged, so they slip and burn out.
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