Take it easy with the dogma. Automobiles and trucks are designs full of
compromise just like boats. Based on your assertion, all heavy trucks, which
routinely tow in excess of 60,000 lbs., would be equipped with automatic
transmissions. Definitely not the case.
Automatics have two very desirable features for towing, both attributable to
the torque converter rather than the transmission itself. The torque converter
provides a fluid coupling between the engine and the drivetrain. This coupling
can provide torque multiplication as much as 1.8:1 which makes it ideal for
yanking your boat out of the water and pulling it up a steep ramp at slow
speed. The other, less obvious, advantage (and the one the manufacturers are
very fond of ) is that this hydraulic coupling acts as a damper protecting the
driveline against all the fore and aft jostling that the trailer causes. This
continual loading and unloading of the drivetrain is more damaging to the
vehicle than the occasional high load caused by pulling the trailer up a ramp
or a steep driveway. Unfortunately, the torque converter lockups used in many
modern transmissions at highway speeds can negate this advantage ( you may
find instructions in your owners manual telling you not to put the selector in
"OD" when towing for this reason).The disadvantage of an automatic is that it
is less efficient, and this we see as waste heat. Hence the addition of
transmission oil coolers with trailer towing packages. Automatics do have
clutches, several of them typically, that's how they change gears and those
cluches will wear more shifting under the higher loads imposed by towing.
There's no free lunch.
Modern manual transmissions will not typically have problems with heat, even
with towing loads. The drivetrain will suffer in other ways though, through
the fore and aft jostling causing accelerated fatigue but mostly in the
clutch. The clutch suffers primarily at the launch ramp, but it is worked
harder every time the vehicle and trailer pull away from a stop. There's no
way around it, more wear occurs. You can think of it as another expense of
boating. Vehicles with a "low" first gear or four wheel drives with a low
range suffer very little if they are operated correctly (without a lot of
clutch slipping). Engines with a lot of low end torque also allow the clutch
to be fully released at a low rpm (again,without excess slippage) are
desirable. Successful towing with a manual requires more skill than with an
automatic. Advantages of a manual over an automatic? Better fuel economy, the
difference is greater when towing than not (fuel economy is the primary reason
heavy trucks still use manual, torque capacity is another reason). Improved
engine braking, important on long descents.
I think most of us who are towing with automatics and most of us who are
towing with manuals are doing so because that it what we had when we bought
the boat . It didn't make a lot of sense to me to pay $2500 for a boat and
then turn around a pay $25,000 for a new vehicle to tow it with. Though I have
to admit that one of the reasons I didn't buy a Catalina 22 (which can be had
in this area for about the same money as a P-15) was that I would need a full
size truck (which I don't have or want) to tow it
My opinion: you''ve got what you've got and hopefully you've got what you
want. Your vehicle is there to serve you, not vice-versa. There are extra
expenses associated with towing - more fuel, more frequent oil changes,
shorter life of the driveline, be it manual or automatic. Overall, I'd have to
say that an automatic IS better suited for towing, but it's not without it's
own set of problems and there are plenty of people (myself included) towing
successfully with manuals.
Best regards,
Dave Kautz
P-15 #1632 " Tilly Lucy"
Mentioned only to provide credibiltiy to the above remarks:
Hardware Development Engineer
Hewlett Packard Automotive Solutions Division
Member Society of Automotive Engineers
yada, yada, yada........
In a message dated 1/21/99 7:40:31 PM Pacific Standard Time,
longyard@ix.netcom.com writes:
> Strictly speaking automatic transmissions do NOT offer infinitely
> variable gear speeds. They only offer the number based on gear sets in
> them. (usually 3 or four). The torque converter's great advantage, and
> the reason ALL PEOPLE WHO PLAN TO TOW ROUTINELY should have ATs is that
> the TC allows for slippage as part of its design. Therefore, you can't
> "burn the clutch". Buying a stick transmission for towing is a very bad
> idea.