The engine is warmed up, but the gearbox? Dangerous mistake of drivers
Today not many people bother to warm up the engine before a trip. And they don’t even think about gearbox. And in vain!
Let’s begin with the fact that it is still desirable to warm up the engine. Ideally, it should reach about 60°C, and then drive.
But if there is no possibility to wait so long, then the best variant is to warm up a few minutes and start driving, not putting big load on the power unit. Any engine warms up considerably faster while running (read – under loading), than at parking.
And what about a gearbox? In fact there is oil in it too, and it gets thick at frost. What to do?
Many owners of cars with a manual probably noticed, how much harder it is to engage the first gear in cold weather. That’s because the oil has thickened from the cold.
Many owners of cars with a manual probably noticed, how much harder it is to engage the first gear in cold weather. That’s because the oil has thickened from the cold.
How to warm up a manual transmission?
Nothing. More precisely, no additional actions for this from the driver are required: it is enough to start the engine. Many people will be surprised, but in a manual transmission most of the parts rotate, dispersing oil even when the car is parked. Unless, of course, the clutch pedal is depressed. The primary shaft and the secondary gears rotate. Similar processes take place in a robot gearbox. And this is quite enough. The fact is that cold operation is not as dangerous for the mechanics as in the case of the automatic. The main inconvenience for the driver is difficult to shift gears. However, 5-10 minutes (depending on temperature outside) of parking with engines on is enough for oil to warm up a little bit and gears will be engaged without excessive effort.
How to warm automatic transmission?
Classic automatic, i.e. hydromechanical gearbox is very vulnerable during work in cold weather. Frozen fluid cannot create the necessary pressure for compression of friction packs, and they start to slip. The torque converter can suffer for the same reason. Thus, it is desirable to warm up automatic before a drive in winter. Some people think, that if the engine is warmed up, automatic is warmed up at the same time. It is far from being so. The classic automat does not warm up at all during parking with a working engine, if the selector switch is in position P or N – the basic warming up takes place while driving. Therefore, it is better to overcome “slowly and sadly” – without sudden speeding up – the first kilometers of a way after cold parking.
But what to do, if right after the beginning of driving you need to cut into the stream on the expressway? Or while parked, your car was buried by a passing snowplow, and now you need to overcome the snow berm at the start? In both examples, increased stress on the automatic cannot be avoided.
We tested and found out how the temperature of automatic transmission fluid changes when parked with the engine running, and whether it is possible to speed up the warming up process.
Our experiment
Measurements were made on Kia Rio of previous generation with 1.6 engine (123 hp) and 6-speed automatic. Air temperature during the test: -4°C.
The measurements were made with a Multitronics C-590 on-board computer. It is connected to the diagnostic connector OBD-2 and allows you to determine not only the temperature of the engine coolant, but also the temperature of the automatic transmission.
The measurements were made with a Multitronics C-590 on-board computer. It is connected to the diagnostic connector OBD-2 and allows you to determine not only the temperature of the engine coolant, but also the temperature of the automatic transmission.
Tests have shown: if the automatic is in N or P mode, the box warms up very slowly. By the time the engine reaches operating temperature, the automatic barely warms up. Take a look at the graph.
Temperature in engine and automatic transmission cooling system at different positions of a selector of a transmission
Warming up is faster if you choose D or R mode. It depends on how the car is parked. For example, very often the car is parked with the rear wheels against the kerb. Then it is safely possible to put in reverse. You should also use the handbrake. Then you can not hold the brake pedal: the car will not roll. But I also do not recommend to leave the driver’s seat to shake off snow from the body: you never know.
It is noteworthy, that the engine will warm up faster. In fact, it is loaded by torque converter, one part of which rotates, and another part does not. That is the engine experiences additional load. And the same intense mixing of the fluid in the torque converter leads to an accelerated warming up of the transmission.
By the time the engine has warmed up to about 80°C, the automatic can also be considered sufficiently warmed up for normal driving. Any design loads are acceptable. Keep in mind that the harder the frost outside, the longer you have to warm up the engine and gearbox.
Is it necessary to warm up the automatic transmission in frosty weather. “What men talk about”(c).
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Good afternoon, dear readers of our blog! This article continues a series of materials based on popular topics and questions that are often discussed on forums on the Internet, as well as asked by telephone to our experts.
We plan to answer the most frequent users’ questions about the structure, operation and maintenance of automatic transmissions in an intelligible and understandable form.
So, what do the men who own cars with automatic transmissions often talk about / ask.
The question of the day is: “Should the automatic transmission be preheated before starting a trip in WINTER (similar to warming up the engine)”.
This is a popular question with the onset of cold weather. Let’s add our five cents to the discussion as well.
So. As usual – to understand the essence, first a little bit of theory of the question. How an automatic transmission works. In contrast to a manual transmission, where the gear is engaged by transferring rotation through several pairs of gears (a simplified understanding, but the essence is the same), in the automatic transmission the gear is engaged by STOPPING one of the elements of the box. That is, one of the elements has to – stop, at the same time releasing the other element. Braking is accomplished by means of a multi-disc friction clutch or friction band. The second important point to understand. The friction clutch properties are STRICTLY defined. That is, the designer when designing clearly defined – at what fluid pressure and for how long the clutch should work (to compress or relax), so that the transfer was engaged in a strictly defined moment! This is important! Third. For friction clutch actuation, the friction properties of the disks and the properties of the oil are important. Oil properties are crucially important in automatic transmissions, and they are strictly defined for every box. That’s why it’s important to use certain oil for this box!
We are done with theory. For those who have finished and have understood :)) – Let’s move on to the essence.
By definition, the properties of cold oil are DIFFERENT from those of oil at working temperature (the working temp of oil in automatic transmission is about 80-90 degrees). Of course it is hard to say by how much, but they are different. Nobody cancelled the laws of physics. And that means that when you start driving, the friction mechanisms will work, but the locking moment can happen a little later, because of the other properties of the oil in cold weather. If the friction clutches are “worn out”, this may be more noticeable. There might be a slight jolt when you engage the gear.
So – what can be recommended EXACTLY – in connection with this: After you start driving in a “cold” box – for some time – do not use intensive acceleration. This may result in more intense slippage of the friction discs (for the reasons described above). And this is probably the basic advice for starting to drive in freezing weather.
Before you start driving, in severe frost, it is often recommended to warm up the box a little bit initially. For this purpose it is enough to start the engine. The movement of the oil in the automatic transmission begins immediately after you start the engine, even if the box is in the “P” position. Some preliminary warming up is not necessary. Nevertheless, if it is very cold, it can be recommended to let the engine work for a while at idle. The oil in the box will also warm up additionally.
Is it necessary to keep the box in “D” position when warming up? The design of the torque converter is such that even when in neutral (P or N mode), the oil will actively move and gradually warm up. If you put it in D (with the car on the brake), heating of the oil in the converter would be a bit stronger (in this mode the oil would get more resistance while working inside the converter, which leads to more intense heating). However, there is also the other side of the coin. If the box is worn out, with a strong increase in pressure of not warmed up oil, you can get the opposite effect and even breakdown. Therefore, it is impossible to give unequivocal recommendation to keep the box in “D” position.
Is it necessary to move the lever in different positions (R, N, D), keeping the car on the brake, will it increase the speed of heating? It doesn’t make sense to “speed up warming up”. What matters to the box is whether to keep it on P/N or keep it on D/R. Moving the lever back and forth is not necessary. Again, you can do harm if you move the lever quickly (which is fundamentally bad for the box, even if the car is stationary).
SO – SHOULD I warm up the automatic transmission? It’s clear from the brief description of the principle of operation of oil in the box that it is not necessary to do this, but it is recommended to do it in frosty weather. It is enough to start the engine and let it run for a while at idle. And in any case – after the start of driving you should avoid sudden acceleration, to give the automatic transmission a chance to warm up a little.
ps to warm up or not to warm up the engine/accessory in frost is a “bearded” question. Proponents and opponents constantly argue. Proponents of “old school” – warm up the engine in winter, change oil after the run-in and pour oil into the filter when changing it 
Love your cars.
We hope this article was interesting. Write your comments!) And you – warm up the box before a trip in the cold?
In the next articles “What men talk about” we’ll tell you about other frequently asked questions of our Clients and readers of the blog. In particular – about other “extremity” – oil overheating. What it is, why it happens, what to do, how to install additional cooling.
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