On 6/27/2019 6:00 PM, jbeattie wrote:
On Thursday, June 27, 2019 at 1:47:46 PM UTC-7, Frank Krygowski wrote:
On 6/26/2019 5:26 PM, wrote:
I see no reason today for manual shifting except for sentimental reasons and that it is cheaper (2000 -3000 euro's). Modern automatic transmission outperform manual shifting in every way, at least the one I'm driving now.

Here's my situation: We drive a Mazda 3. We have a tiny pop-up camping
trailer. It weighs only 750 pounds empty.

The Mazda's stated towing capacity is zero, although I've been told that
if I had bought the exact same vehicle in Europe, it's towing capacity
would be listed as 500 kg, which is plenty.

I put a trailer hitch on this car as soon as I got it, and we've towed
the trailer as far as Nova Scotia. I knew I was violating the warranty,
but I judged it worth the risk. If the car had an automatic
transmission, I don't know if I'd make that same judgement.

Why? Towing trailers in hilly terrain is a clutch killer, and typically cars with ATs have higher towing capacity than the same model with a MT because of the AT torque converter. I don't see why having a MT would make you feel more positive about towing -- particularly on a car that probably has a pretty low-torque first gear since it is just a family sedan and not a truck.

I admit, I haven't looked into this deeply. But I know that transmission
coolers are sold as accessories for automatic transmissions used in
towing:
https://www.aamcocolorado.com/what-y...ssion-coolers/
That gives me pause, especially with the warranty issue.

Perhaps those coolers aren't quite as important in these days of locking
torque converters, but my understanding is that they lock up only at
cruising speed; so if I were towing slowly up a mountain, I'd think
there would be a potential for transmission overheating. And we have
towed this trailer over the Appalachians and Rockies many times.

The Mazda is the fourth little car with which we've towed this same
trailer, all with manual transmissions. (I've never owned an automatic.)
None had any transmission problem, and only the last one, the Pontiac
Vibe, ever had a clutch problem, a very slight occasional slip once it
was 10+ years old. But since slipping clutches were a known issue with
old Vibes, it probably had little or nothing to do with the towing.

Regarding torque: There's always been enough to climb mountains, etc.
even when the car towing this trailer was a 1985 Honda Civic. We just
went up fairly slowly in a low gear. I the manual transmission didn't
seem to care. I suspect an automatic trans might.

--
- Frank Krygowski