Can you rest your hand on the gearshift knob while driving without it harming your transmission? That's a question that is hotly debated both on the web and off. And, as is normal with these types of disagreements, both sides are utterly convinced their opinion is the right one.
Those who say you shouldn’t do it will insist that it causes either the selector fork to rub against the rotating shift collar, resulting in damage, or that it will at least wear out your synchros prematurely. Those are the typical answers you’ll find in everything from owner’s manuals and public radio’s Car Talk to endless YouTube videos weighing in on the topic. But do these arguments stand up to science and engineering principles? Let's take a close look at both sides of this controversial topic.
Why Some Say That Resting Your Hand on the Shifter Knob is Bad for Your Transmission
Here’s a video from Engineering Explained that discusses why many people firmly believe that it is bad to rest your hand on the gear shift in a manual transmission vehicle. The narrator of the video explains his reasoning quite clearly, starting with a good discussion of what goes on when you shift gears.
When you are shifting gears, you are essentially pressing a selector fork (aka, shift fork) against a rotating shift collar. The shift collar is then pressed into the gear you choose, and a gear change occurs. During this process, you have a non-rotating object that only moves back and forth (the selector fork) pressing against a rotating component (the collar). This will naturally result in wear on the selector fork whenever you shift gears because it will rub against the rotating collar (which is typically going to be rotating at fairly high speed). This wear won’t be very significant for two reasons: (1) it only occurs when you shift gears, and (2) the selector fork is only in contact with the rotating collar for an extremely short amount of time.
However, the narrator then states that if you leave your hand on the gearshift while it is in gear you are causing pressure to be applied to the selector fork. This pressure, according to the video, is enough to cause it to rest against the rotating collar. By resting your hand on the gearshift, that contact occurs for an extended period of time instead of less than a second.
Based on their logic, this extended contact between the selector fork and the rotating collar causes a significant increase in wear for the selector fork which will result in it needing to be replaced far sooner than normal. And at first blush, this theory seems to make good sense, doesn’t it?
You’ll see similar statements in some owner’s manuals, often in the form of a warning against using the gearshift lever as a hand rest because it will cause premature wear of the selector forks (or transaxle shift forks, as they may sometimes be called). It can't be safe if the manual says not to do it, right?
A blog post on CarThrottle makes a very similar argument. According to the post, resting your hand on the gear selector knob transmits forces that cause the selector fork to come into metal-to-metal contact with the rotating collar. The result of this is premature wear and damage to both the selector fork and the dog clutch collar. They go a bit further, though, and state that resting your hand on the shifter can even snap the selector fork! Snapping or even bending the selector fork is obviously much worse than just causing it to wear out too soon. It sounds like it could cause some serious damage to your transmission on top of what it does to the selector fork. Taken at face value, this argument seems like reason enough not to rest your hand on the gearshift.
So, in summary, proponents of this view believe that resting your hand on the gearshift forces the selector fork to contact the rotating collar, which results in premature wear of the selector fork or, even worse, a bent or snapped selector fork.
What’s Wrong with this Argument?
While the case against resting your hand on the shifter sounds reasonable on the surface, there are a few holes in the theory if you dig a bit deeper.
The gearshift knob is not attached to the transmission directly. Instead, it is attached via a linkage or, in the case of many FWD cars, a cable – but not directly. This is key!
A video by KYLE.ENGINEERS in response to the Engineering Explained video posted above illustrates this precisely. Take a look, and you'll see exactly how the shift knob is separated from the actual shift collar, and how force from resting on or jostling the shift knob is not transmitted further into the transmission:
As you can see, in the case of a linkage, the downward vertical force that results from the weight of your hand is going to be absorbed by a ball joint or by ball bearings. Ball bearings and ball joints are actually designed to prevent these types of forces from being transferred any further. The vertical force will never reach the selector fork, much less force it against the rotating collar.
In the case of a cable, the downward force also has no effect. It won't reach the selector fork. The kind of vertical force that results from a hand resting on the gearshift will not cause any extra wear for the selector fork or rotating collar because it is not directly transferred to any part of the transmission. Not only will the selector fork not be in danger of premature wear, but it won't be bending or breaking, either.
In FWD cars, the shifter is generally attached to the transmission via cables. As a result, there is play in the gearshift, usually left-to-right and front-to-back. When moving the gearshift, there are two levels of resistance: the first level is overcoming the play, and the second level occurs as the selector fork starts to be moved.
What about RWD vehicles? Is it dangerous to rest your hand on the gearshift in those type of automobiles?
Even in rear wheel drive vehicles, the shift knob is only connected to the transmission via a linkage. The weight of your hand still won't damage the transmission or any of its components. There is still enough play in the knob before the selector fork itself is moved. That play keeps you from accidentally changing gears. It takes significant effort to move the gearshift into another gear, which means that it takes quite a bit of force to actually engage the selector fork. If you've ever driven such a vehicle, you know that you can't accidentally shift gears. The driver definitely knows when the selector fork starts to be moved, as the effort required to move the gear shifter increases dramatically.
That second level of resistance obviously requires a greater force, and drivers recognize intuitively that it means you are actually changing gears (or more precisely, moving the selector fork). It takes more force than just resting your hand on the gearshift to successfully engage the selector fork, otherwise it would be common to pop out of gear when resting your hand on the shifter (if this EVER happens, then you definitely are doing something wrong). The selector fork only moves and engages the shift collar if there is significant forward/backward force applied to the gearshift knob. Again, the downward vertical force from your hand isn't going to result in a gear change and won't affect the selector fork.
Now we come to the issue of bending or snapping the selector fork, as CarThrottle warned about. Under normal circumstances, nobody is going to be bending, much less snapping, a selector fork. Even a person with superhuman strength would have to be extremely aggressive while shifting gears and generate something besides a downward force in order to snap a selector fork.
If your hand's weight on the gear shift were enough to bend or break the selector fork, then we would be seeing many, many broken selector forks on cars – which we don't. It just isn't a common repair on manual transmission vehicles. That's because under normal driving conditions (even with your hand on the gearshift!), the selector fork will never bend, much less snap in two.
The only selector fork that is in danger of bending or snapping is the one found on motorcycles. This can happen because (1) the shifting is being done with the foot, allowing the driver to apply much more force with a great deal more impact than is possible by hand, and (2) the components involved are much smaller than would be found in an automobile.
But What About the Synchronizer Rings?
You've probably also heard that resting your hand on the gearshift knob will wear out your synchronizer rings (even if it doesn't affect the selector fork). We’re here to tell you that that claim isn't true, either. You can't damage the synchronizer rings by merely placing the weight of your hand on the gearshift.
A synchronizer ring (often called a synchro ring, synchro mesh, synchro, or blocker ring), brings the gear and the selector to the same speed (or “synchronizes” them, hence the name) through friction and contact. Synchro rings make it possible to make a clean shift without any grinding. Synchro rings also successfully replaced the need for double-clutching. Because synchro rings use friction, however, they wear out relatively quickly due to the metal-to-metal contact involved.
Synchro rings are actually designed to be the first thing that wears out inside the transmission. Note that they are made of brass, which is much softer than the metal parts they interact with. Synchro rings will therefore wear out before the parts they make contact with. And that's a good thing, too, because they are much cheaper than the hardened steel parts they come into contact with. Significant wear is normal for synchro rings; however, that wear does not occur as a result of vertical force from the weight of your hand on a gearshift.
Unless pressure is being put on the selector fork/collar, these parts – the synchronizer ring, the selector fork, and the rotating collar -- will not rub against each other. If they aren't rubbing against each other, the they aren't experiencing wear. If rubbing was going to occur every time you rest your hand on the shift knob, this entire collection of parts would wear out faster than anything else in your manual transmission. But they don't.
No rubbing/contact occurs unless someone is pushing forward or backward while resting their hand on the knob. If you apply a force forward or backward (toward or away from the engine), it can engage the selector fork. In that case, you will engage the synchros and cause them to wear out. But without the selector fork engaged, no damage will occur to the synchro rings. So that means that a vertical force, such as that from the weight of your hand, is simply not going to make your synchro rings wear out too fast.
There are things that can make synchro rings wear faster than normal, however. A good example is getting an abrasive substance, like dirt or sand, inside your transmission. Other sources of premature synchro wear include improper clutch adjustment, using the wrong type of lube, and bad habits such as powershifting. These are far more likely to wear out the synchro rings than resting your hand on the gearshift.
In order to cause damage (prematurely worn fork pads, and 5th gear synchro rings/gear teeth), the driver must be applying steady and serious forward or backwards pressure on the knob while resting on it. While causing this wear, the driver would be receiving constant physical feedback from the shift knob. The moral of this story should not be 'don't rest your hand on the shift knob', it should be 'don't constantly push or pull on the shift knob while driving'. And that is very different and easy for any driver to avoid -- even if they like to rest their hand on the shifter.
The synchro-ring-wear subset of this myth is likely born of confirmation bias. Synchro rings are generally the first part to wear out in a manual transmission, and they are designed to wear out sooner than other parts. It's better to replace relatively inexpensive synchro rings made of brass than it is the more expensive hardened steel parts they interact with. That said, it should be pointed out that in a well-treated transmission they can be expected to last 150-250k miles without issue. But since they do wear out faster than other parts, it makes sense that drivers would look for something to blame this wear on.
How long a manual transmission lasts is dependent on how well the transmission is treated. Bad practices such as aggressive shifting (especially power shifting) and routinely bad rev-matching (such as is common with novice operators of manual transmissions) will dramatically shorten the life of these components. It’s easy (and often convenient) to mistakenly attribute early wear to resting your hand on the shift knob, which is a red herring, rather than on mistreatment of your transmission.
Are Weighted Shift Knobs Bad for a Car?
There's one other myth we hear now and then that we'd like to address. Many people like the feel of a weighted shift knob and the smoothness they bring to their shifts. But, they often get warned that their weighted shift knob will damage their transmission and cause it to wear out too soon. That sounds familiar, doesn't it?
The truth is simple: Weighted shift knobs will not damage your car's transmission for the same reason that resting your hand on the gearshift won't damage it. The force from a weighted shift knob is vertical and acts downward. Any other directional forces will be completely countered by the gear selector springs. As we have already discussed, none of these forces will cause the selector fork to engage with the rotating collar. It also will not cause the synchro rings to wear out faster.
To Sum it All Up
Resting your hand on the gearshift will not cause your transmission to wear out prematurely, contrary to popular belief. That myth is based on a misunderstanding of transmission design, and the false notion that the gearshift directly engages with the transmission.
Even if the gearshift did directly engage the transmission, it still has enough play to prevent accidentally moving the selector fork. There are also those who claim you can wear out your synchros with your hand on the gearshift. The truth is that no damage will occur unless the selector fork is engaged, and it won't be engaged by a vertical force or the weight of a human hand. The same is true for a weighted gearshift knob: It won't damage your transmission.
So, feel free to rest your hand on your gearshift – even with a weighted gearshift knob – because it truly will not damage your transmission. What does damage transmissions is poor treatment, such as bad rev-matching, aggressive shifting, and neglecting regular maintenance. If you use common sense when driving a manual and keep up the maintenance, you shouldn't have any major problems.