Automatic transmission: questions

chavvdarrr

Veteran
So, I had never "used" car with truly automatic transmission.
And I have few questions which I can't find written answer for.
Like:
Towing - is it possible, what conditions? (so far I've read that towing car with CVT, without front wheel lifted up, is allowed for no more than ~40km with speed <50km/h, not sure if same is true for classic automatics)
Stopping on red lights - shifting to N is ok or not? Some people declare its ok, some claim it will likely damage the transmission (not immediately of course)

Hmmm, I'm sure there were other things i always wanted to know about automatics but was too afraid to ask, so feel free add any useful, non-trivial info ;)
 
Towing - is it possible, what conditions? (so far I've read that towing car with CVT, without front wheel lifted up, is allowed for no more than ~40km with speed <50km/h, not sure if same is true for classic automatics)

I've only had one old car with 'classic' AT. Don't know about CVTs, but certainly for 'classic' ATs with hydraulic torque converter you really must avoid towing. If engine is not running and the hydraulic oil is not circulated, the spinning wheels cause the torque converter to overheat the oil in it. Only a short distance with slow speed, just as you've read.

Stopping on red lights - shifting to N is ok or not? Some people declare its ok, some claim it will likely damage the transmission (not immediately of course)

Again, for hydraulic ATs (no idea of CVTs): If you do not shift to N, temperature will rise. If you do, it is causing a bit of wear in AT every time you do it. One should follow common sense and what the instruction manuals tell you: If you need to stay stopped for a long time, shift to N, but do not do that every time you stop in red lights when you know you will be soon moving again.

I hope someone with insight to modern CVTs can shed light on them for you.
 
It is rather pointless to shift to neutral while stopped for just a few minutes at a light or in traffic. All that shifting for the auto will cause wear and tear and if you do it repeatedly at stop lights throughout the day it will add up pretty quickly. I'm not fully aware about CVT transmissions, but I imagine _xxx_ will be able to shed more light on the issue.
 
So, I had never "used" car with truly automatic transmission.
And I have few questions which I can't find written answer for.
Like:
Towing - is it possible, what conditions? (so far I've read that towing car with CVT, without front wheel lifted up, is allowed for no more than ~40km with speed <50km/h, not sure if same is true for classic automatics)

In general, avoid towing on the driven wheels even when in N for any distance & at speed. There are some differences between transaxles (FWD) & transmissions (RWD) & for AWD variants of both of these. Planetary gearsets/clutch to clutch or one way freewheeling rollers/"clutch packs" are likely unaffected, but the classic "Powerglide" transmissions should have the driveshaft decoupled for any distance towing. I believe FWD can use lock/freewheeling axles. Kits are probably available for both. Some transmissions (esp 4WD) can be trashed if towing on the driven wheels & you've previously shifted from R to N. CVT can be more limiting, but check with manufacturer's handbook. It's always best to use a flatbed truck anyway. You may have more problems with a LSD in any case...

Stopping on red lights - shifting to N is ok or not? Some people declare its ok, some claim it will likely damage the transmission (not immediately of course)
Don't bother, unless stuck on a hot day for >5mins after bumper/bumper traffic. The stall converter is usually set ~1200rpm for normal use prior to full TCC lockup. There's little gain & modern transmissions employ neutral idle anyway. A transcooler is always a good idea though.
 
Depending on the construction there could be some drag on the torque converter when towing, but usually nothing critical - I guess older constructions could have problems here. With dry or wet clutches it's way less, thus uncritical. Not sure about CVT, didn't work with those thus I never bothered asking.

Shifting to N when stopped is a waste of fuel (shift to N and back from N requires some energy), other than that you can do it as much as you want. Nothing happens except for the usual wear and tear.

EDIT: looks like I was talking out of my arse considering towing: our current automatics are also falling into 50km/50kmh category, with double clutch transmissions it's a bit more. The gearbox-colleague said it's always a problem because of heat - when the engine is not running, the clutches will burn out eventually because there is no active cooling.
 
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Wow, I feel lost. Are you asking if you can tow an automatic vehicle with all the wheel (including drive wheels) on the ground or are you asking if you can tow another vehicle or object with a vehicle that is an automatic?

I never actually realized that there were limits to how far/fast you could tow an auto with all 4 wheels on the ground. We would just put it in neutral and carry on. I suppose I learned something new.
 
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