PT36 retarder & other things

[sfedeli3]

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
> > >
> > >
> >
>