Re: Fw: tricky -tranny

["David Teitelbaum" <jtrealty@xxxx>]

The friction plates (clutch discs) in an automatic transmission aren't
all that much different then a manual "wet" clutch. Most people are
familiar with the "dry" type as in most cars but "wet" ones are in
heavy equipment like trucks. In an automatic transmission the plates
are cooled and lubricated by the trans fluid. The trans fluid also is
used in the cltch pack pistons to apply pressure to the plates to
engage them. Without enough pressure the clutches slip. In an
automatic the plates are not meant to be slipped anywhere near as much
as in a manual transmission. The torque converter is there for that.
In an automatic the clutches are really more like on-off devices
leaving the torque converter to match the engine speed with the
transmission, not the clutch packs. In any case the amount of friction
materiel that is in the pan is a function of mileage, if there is a
lot at low mileage you are in trouble. Also if there is any
significant amount of metal that is bad news, especially if it is
magnetic. As the trans wears inside you will get brass-bronze from the
bearings and thrust washers but you should not see cast iron,
alumiunum, or steel from the case or the gears. This is why it is
important to open the filter and actually see what is going on inside.
As for the fluid, if it smells burnt it has lost it's lubricating
properties from being overheated. This happens when the clutches slip
and burden the fluid with particles of friction materiel and break
down the fluid from the heat. It won't lose it's capability as a
hydralic fluid, ie: it is still incompressable, but it can't lubricate
the bearing surfaces properly so now you start a cascading failure
ruining the "hard parts" like gears and housings. An external sign is
leaking seals. When the fluid is overburdened with particles it is
like grit and that grit eats out the seals resulting in fluid leaks.
When you see this it is already too late. Replacing the seals now is
like rearranging the deck chairs on the Titanic. The bottom line is
NEVER DRIVE AN AUTOMATIC TRANSMISSION THAT SLIPS. You will cause MAJOR
(read expensive) internal damage. This advice is good for any
automatic transmission, not only in Deloreans.
David Teitelbaum
vin 10757



--- In dmcnews@xxxxxxxxxxxxxxx, "content22207" <brobertson@xxxx> wrote:
> Clutch discs in automatic transmission totally different than friction
> plate in manual. Are not supposed to touch anything. Transmission
> fluid itself forms coupling. That's why it's so important to keep
> clean, unburned (like brake fluid, once you overheat it loses
> hydraulic properties), not foamy (don't overfill), etc. If you lose
> hydraulic coupling, discs will wear out very quickly. Don't know about
> DeLo tranny, but nearly all of its contemporaries can drop pan and
> look for collecting disc debris. If it's there, get ready to rebuild.
> 
> Bill Robertson
> #5939