5 Common Myths About Automatic Transmissions
Automatic transmissions are something of a mystery to many, including a lot of the automotive industry itself! Because of this, there are many myths—or more accurately, a lot of misinformation—about automatic transmissions that get traction because there are simply not enough voices who know better and are inclined to set the the record straight. And that’s why this article is here.
In this article we’re going to go through some of the more common myths and misunderstandings about automatic transmissions and look at why they’re true, false, or a mix of both. Not to mention why.
Automatic Transmissions are Sealed Units
Don't mess with them, they're not a repairable part!
Automatic transmissions are not a serviceable or repairable component. When something goes wrong, the only thing you can do is fork out the cash for a replacement transmission.
No automatic transmissions are unrepairable, and most benefit from servicing (some even require it).
As hinted at the top of this page, automatic transmissions are a bit of a black art to those who don’t work with them. These days you can easily find a dozen mechanics in any populated area, but the chances of finding one who knows automatics and is prepared to work on them is pretty slim.
In truth, people who do know automatic transmissions can often be a bit cagey about repairing one for the simple fact that it’s so easy for something to go wrong. Autos contains lots of small-but-important parts—such as tiny springs and ball bearings—that can easily be left out in a moment of lapsed concentration. This is why many mechanics won’t touch autos, and why dealers will only ever replace them.
So, while it’s technically a myth that automatics are non-repairable, in practicality it may seem to be the case. It’s all a matter of finding the right technician.
Automatic Transmissions are Less Fuel Efficient than Manuals
Automatic vehicles are greedy, fuel-guzzling monsters.
Automatic transmissions are heavier, create more drag on the powertrain, and generally cause the vehicle to use more fuel than if it had a manual transmission.
This one, unfortunately, is totally true. Manufacturers are working to close this efficiency gap between automatic and manual transmissions, but even the most fuel-efficient automatic transmission of today will still fall short of a manual in like-for-like use cases.
It’s all to do with weight and friction. As a general rule, automatic transmissions are heavier than their manual counterparts. That part of the equation is pretty straight forward: additional weight means more work for the engine in any given situation, and that means more fuel.
The friction thing is a little more complicated. Inside a manual transmission there are a series of metal gears that are coated in a thin layer of lubricant. The interface between the transmission and the engine is a dry clutch, which feels little to no resistance when it is disengaged.
Conversely, an automatic transmission uses a series of wet clutches that are constantly bathed in transmission fluid, which acts as both lubricant and hydraulic fluid. This means that even when a clutch is not applied, it still faces some resistance from friction. It’s not much, but the cumulative effect when compared to a manual transmission is noticeable. That being said, automatics will often change gear at the most efficient time (unless in some kind of alternate driving mode is in effect, such as “sport” mode), so they can still be more efficient than a manual if the driver of the manual isn’t very good at hitting the optimal shift time.
Automatic Transmissions Don’t Work in Poor Driving Conditions
Snowing? Best leave the automatic at home...
Automatic transmissions can’t handle difficult driving conditions, particularly snow, and will make driving awkward.
This one was true but has almost been completely nullified by advanced technologies and improved control methods.
Automatic transmissions are controlled by an electronic “brain” of sorts. It takes information from all over the vehicle—things like wheel speeds, throttle pedal position, vehicle incline—and decides what gear to be in. For most of the history of cars, this brain has been pretty simple. Where a driver of a car with a manual transmission can intuitively adjust their driving style to suit the road conditions, a transmission control module typically just isn’t smart enough to make such calculations.
This is especially true of older automatic transmissions which didn’t even have a control module, and shifting was controlled mechanically using the rotation speed of the engine and transmission output shaft.
Quite early on, however, transmission manufacturers began to get to grips with this problem. From a simple “snow” button that tells the transmission to set off in second gear, right through to the latest all-singing-all-dancing driving comfort systems that actually detect road conditions themselves and adjust without the driver having to so much as press a button.
Generally speaking, though, if your car is relatively modern, you should be fine in most driving conditions.
You Should Put Your Automatic Transmission in Neutral When Stopping
It's just better for the transmission, car, and your own piece of mind.
You should always shift to neutral when you come to a stop—like a red light—because leaving it in drive will cause additional wear on the clutch and use more fuel.
This one, in practice, is false. It may have been the case with much older transmissions, but almost any transmission with electronic components is fine to leave in drive.
Automatic transmissions, as mentioned above, are working with very limited decision-making ability using a very limited set of data values. The transmission can’t see what’s in front of you, or if there are traffic lights coming up. It only knows that you’re pressing the brake pedal and the car is slowing down. The fact that when you lift your foot off the brake pedal the car begins to pull away has led many to believe that the drive is engaged even when you’re at a standstill.
The truth is all modern transmissions compensate for this. Often with a neutral engagement whenever the vehicle is stationary and the brake pedal is depressed. In fact, if you’ve ever driven an automatic vehicle that bumps when you come to a stop, or as you move away from stationary, that is probably an issue with the neutral engagement mechanism.
In all likelihood with modern automatic transmissions, you’re probably more likely to damage the linkage mechanisms between the transmission and the gear selector from excessively moving in and out of neutral than you are to damage any internal components by staying in drive while in traffic.
You Can’t Tow an Automatic Vehicle
Call the low-loader...
Towing an automatic vehicle will cause components inside the transmission to lock up and/or become catastrophically damaged.
Yes and no. Read on…
There are a few things to consider here. First is the way an automatic transmission fundamentally works. It needs hydraulic pressure in order to do anything, and that pressure is usually created either by a pump driven directly by the engine, or a standalone electric pump. Without that hydraulic pressure, no internal components can be applied, and so nothing inside the box can operate. This means there is little to no risk of a clutch burning out due to the vehicle being towed.
The pump doesn’t just provide hydraulic pressure, it also moves transmission fluid into places to serve as lubricant, such as in planetary gear trains. This is a crucial aspect for these components as, without the lubrication, the gear train would eventually break up. The relevant aspect here is that some gear train or another will almost certainly be turning with the output shaft of the transmission. Or, to put another way, if the driving wheels are turning, something hefty and metal inside the transmission will be turning as well.
So first of all, if you’re towing a vehicle with the driving wheels off the ground, you don’t need to worry about a thing. If your car is two wheel drive and the two wheels that do the driving aren’t touching the road, the transmission will never know it’s been towed.
Secondly, check your manufacturers handbook. Some manufacturers instruct you to add additional fluid to the transmission and remain below a particular speed when towing. This gets around the risk of the aforementioned gear trains breaking up. Others will simply tell you the vehicle cannot be towed at all.
Finally, always, always make sure the vehicle is not in park before any towing attempt. Unlike the clutches and lubrication circuits, the park mechanism is a simple lump of metal that locks into some big chunky teeth directly connected to the output of your transmission. It doesn’t need hydraulics, so park is just as effective with the engine off as it is with it on. If you try and tow an automatic in park, the best case scenario is you drag the vehicle with locked up wheels and wreck the tyres. More likely, however, you’ll bend and/or break something internally.
And there are my five common myths about automatic transmissions. Do you have a question about what you can and can’t do with automatic transmissions? Perhaps a myth of your own to debunk or confirm? Why not speak up in the comments below?
© 2017 John Bullock