Re: [A/S] Automatic vs manual transmission

["chyde" <chyde@xxxxxxxxxxxxxx>]

Bill,
 My 87 Diesel Suburban came with a factory transmission cooler built into
the oversized radiator. The vehicle is a 3/4 ton with an 8600 lb gvwr and a
4.10 diff. I run a vehicle development business in Upstate NY and in my
employ is an ASE certified Mechanic/Transmission Specialist who grew up in a
family owned transmission shop. This guy has been rebuilding Auto Trans
since he was a young man. He says that typically what a manufacturer
recommends and installs for towing purposes is very under sized to what is
really needed in the real "towing" world. What he recommended was that I
keep the factory set-up and add "in series" a large "True Cool" oil cooler.
As the factory cooler runs within the radiator coolant, this allows the
trans oil to reach operating temperature quicker in the winter, which is
good for the health of an Auto Trans.(Running too cold can be a killer as
well)  The True Cool design is quite unique in that it is self regulating.
The passages within the cooler are very small which don't allow oil to pass
through when its cold. In this situation the oil bypasses the main cooling
area and out the other side and back to the transmission. As the oil heats
up, the oil thins out  enough to pass through the very small orifices into
the cooler itself and allowed to cool. It really is self regulating based on
oil viscosity variations.
 Another thing he recommends is that you get the fluid and filter changed
every couple of years. Don't do the cheapy "drop the pan, change the filter
and fill it up again method" as this leaves a considerable amount of dirty
oil in the torque converter. Transmission specialty shops have machines much
like a "Dialysis" machine that will pump/circulate and filter all of the
trans oil out of the tranny. It's expensive but it insures  very clean
internals even as clutch packs, bearings etc wear in the normal cycles of
driving. Keep in mind that there are dozens of very small passages, valves,
orifices, pressure sensors etc which make up the guts of an Auto Trans and
if any one of these gets plugged in any way, even for a short period of time
can spell disaster for your Transmission. I have no connection with True
Cool.
Colin Hyde
87 Diesel Suburban with a Banks "Sidewinder" turbo
57 Sovereign of the Road
59 Ambassador International
WBCCI, VAC, 10247