PT36 retarder & other things

[Rob Robinson]

I'm with you Shane on the annual tranny fluid change. I use Transynd and
change the spin on filter each time. I leave the sump rock catcher in place.

On 23/08/07, sfedeli3 <sfedeli3@...> wrote:
>
> Hi All,
>
> My tranny reading is regularly 230 degrees. Of course, it could be
> a faulty sending unit, but my engine oil temp is around the same too,
> if not a little warmer. I would expect both oil sumps to be pretty
> close in temperature and seem to recall the blue book indicating that
> 200 to 250 was the normal operating temp for the Allison that I have.
> In any event, I change the fluid annually. It's relatively cheap and
> easy to do on the mid-80's PT models. You just need a BIG bucket.
> Varying brands of tranny fluid have different flash points and
> additives. I've been using Lubrication Engineers
> [http://www.le-inc.com] 7500 MONOLEC® Power Fluid in numerous vehicles
> for a number of years with great results and never smell burned fluid
> when I drain. If you're really concerned about the tranny temps, or
> drive the western Rockies, get a Jacobs Engine Retarder.
>
> Shane Fedeli
> 85PT40
> Hershey, PA
>
> --- In WanderlodgeForum@yahoogroups.com,
> "davidkerryedwards"
> wrote:
> >
> > I found this on another website:
> >
> > Why Atf Wears Out
> > An automatic transmission creates a lot of internal heat through
> friction: the friction of the
> > fluid churning inside the torque converter, friction created when
> the clutch plates engage,
> > and the normal friction created by gears and bearings carrying their
> loads.
> >
> > It doesn't take long for the automatic transmission fluid (ATF) to
> heat up once the vehicle
> > is in motion. Normal driving will raise fluid temperatures to 175
> degrees F., which is the
> > usual temperature range at which most fluids are designed to
> operate. If fluid
> > temperatures can be held to 175 degrees F., ATF will last almost
> indefinitely -- say up to
> > 100,000 miles. But if the fluid temperature goes much higher, the
> life of the fluid begins
> > to plummet. The problem is even normal driving can push fluid
> temperatures well beyond
> > safe limits. And once that happens, the trouble begins.
> >
> > At elevated operating temperatures, ATF oxidizes, turns brown and
> takes on a smell like
> > burnt toast. As heat destroys the fluid's lubricating qualities and
> friction characteristics,
> > varnish begins to form on internal parts (such as the valve body)
> which interferes with the
> > operation of the transmission. If the temperature gets above 250
> degrees F., rubber seals
> > begin to harden, which leads to leaks and pressure losses. At higher
> temperatures the
> > transmission begins to slip, which only aggravates overheating even
> more. Eventually the
> > clutches burn out and the transmission calls it quits. The only way
> to repair the damage
> > now is with an overhaul -- a job which can easily run upwards of
> $1500 on a late model
> > front-wheel drive car or minivan.
> >
> > As a rule of thumb, every 20 degree increase in operating
> temperature above 175 degrees
> > F. cuts the life of the fluid in half!
> >
> > At 195 degrees F., for instance, fluid life is reduced to 50,000
> miles. At 220 degrees,
> > which is commonly encountered in many transmissions, the fluid is
> only good for about
> > 25,000 miles. At 240 degrees F., the fluid won't go much over 10,000
> miles. Add another
> > 20 degrees, and life expectancy drops to 5,000 miles. Go to 295 or
> 300 degrees F., and
> > 1,000 to 1,500 miles is about all you'll get before the transmission
> burns up.
> >
> >
> > Kerry
> > 82 FC 35
> > Denver
> >
> >
> > --- In WanderlodgeForum@yahoogroups.com,
> "davidkerryedwards"
>
> > wrote:
> > >
> > > Those temperatures seem really high to me. I was looking at hose
> temperature ratings
> > > and fluid temperature ratings when I was redoing my power
> steering. My recollection is
> > > that standard hydraulic hose was rated to 250 degrees and the
> expensive high
> > > temperature hose was rated to 325 or 350. I think regular
> transmission fluid was rated
> > as
> > > functional up to about 250 degrees and synthetics up to about 350.
> These numbers are
> > > from my memory, If anyone else has knowledge about the functional
> temperatures of
> > > transmission fluid, I'd like to know. I'd be quite concerned with
> temperatures over 300
> > > degrees.
> > >
> > > Kerry
> > > 82 FC 35
> > > Denver
> > >
> > > be sure to keep it below
> > > > 320-330 degrees or you'll shorten the life of the tranny fluid
> > > > greatly. Most commercial bus drivers have to change the tranny fluid
> > > > every 50K miles when using the tranny retarder often. Mine
> easily goes
> > > > from 230 to 300 degrees when descending a steep off-ramp. One way to
> > > > slow the heat is to engage the fan override and let the hydro
> fan rob
> > > > 25-30 horses from the engine and cool the tranny fluid a little
> > > > quicker. On an off-ramp it does not make much difference, but on
> the 3
> > > > or 4 mile grade, you can usually make it to the bottom under 320
> > > > degrees if you also use the service brakes along with the tranny
> brake
> > > > and fan to slow the coach down.
> > > > Shane Fedeli
> > > > 85PT40
> > > > Hershey, PA
> > > >
> > > >
> > >
> >
>
>
>



--
Rob, Sue & Merlin Robinson
94 WLWB


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