How to Fix Bad Synchros? Here’s What You Can Do.

Something has been grinding your gears lately? While it can happen even to the best drivers out there, it might not always be you the one that has been grinding your own gears. Manual gearboxes might seem like complicated components in a vehicle, but when compared to an automatic gearbox, things become much simpler to understand.

Now, we think it's time to explain the first question. Manual gearboxes have some components called synchronizers, commonly known as synchros. Their purpose is to adjust the speed of the gearbox shaft so that the gears are quicker to align whenever you are shifting.

Not only does this provide a much smoother driving experience, but it also eliminates the need to double-clutch. This technique was necessary when shifting gears in older vehicles, as they lacked synchros. Let's now investigate why synchros fail, how to recognize bad ones and how to solve the issue.

Why do synchros fail?

Synchronizers, like pretty much all the components in a car, are parts that can wear with mileage, so it's not uncommon for them to start struggling on very high-mileage cars. Don't get me wrong, they are not supposed to be changed regularly, like filters and spark plugs, but they might not last as long as your engine, so if your vehicle has driven multiple times around the planet, you can expect them to give up one day.

Worn gear teeth will no longer be able to mesh together as they should and that might result in a very unpleasant grinding noise. Also, do not forget the fact that there's oil in the gearbox, and, as we are sure you already know, the oil loses its properties over time and with use.

When the oil no longer does its job properly, the gears will start grinding on each other instead of grinding on a very thin layer of oil. This will result in small metal shavings that will deteriorate not only the synchros but the entire gearbox with time. Lifetime gearbox oil still sounds good to you?

Another reason for their failure can be driver error. Slamming through the gears definitely won't help the synchros over the long run, so please keep this in mind when going to your local track. Are you resting your hand on the gear lever when driving? You might be surprised, but this also contributes to wear, so we advise you to only touch the gear lever when necessary.

If your car has low mileage and you are sure that your driving technique doesn't harm the gearbox in any way, it is safe to assume that the reason for the synchros failing is simply bad quality.

From time to time, it happens (even to the highest quality brands out there!) that the materials used are simply not good enough or that quality control had a day off when they were building your car.

How to recognize a bad synchro?

While every manual gearbox has a different feeling to it, if you are used to driving cars equipped with such transmissions, you are probably familiar with how they should feel when they are operated and so, you are probably going to notice when something doesn't work as it should. Here are a few symptoms of bad synchros:

• Increased shifter resistance - You've probably realized that whenever you were shifting the gears, you felt that the gear lever almost pulled itself into the gear that you wanted to select. If you suddenly find that there's more resistance to the shifter and you almost have to force it into gears, you might have a worn synchro.
• Grinding noises - Another very common symptom of a failed synchro is the dreaded grinding noise you get when shifting into a certain gear. Also, if this only happens on a certain gear, it's safe to say that that gear's synchro is faulty, and not the entire transmission.
• Whirring/humming noises - Again, if the weird noise you're hearing is only there in certain gears, it might be the cause of a bad synchronizer.
• Shifter popping out of gear - If you were driving as you normally do and then, all of a sudden you heard a strange noise and the gear lever popped out of gear, it can be because of a failing synchro. Not only is this a symptom you can't miss, but it's also something that can be potentially dangerous, so please try to have this fixed as soon as possible.
• Transmission stuck in gear - This is also something that could be very dangerous, so if you experience this, it's better to stop the vehicle and have it towed to the nearest shop.

Can you drive like this?

In a word? Yes. Do you want to? Probably not, as the driving experience will be severely impacted, resulting in slower and less smooth gear shifts. Most of the time, synchros fail on individual gears and not on all of them.

For example, you might have grinding noises only when shifting into second gear, but the rest of them will be perfectly fine. Things should be fine if you shift slowly or if you use the double-clutching technique we mentioned earlier, but it's definitely not a good idea to drive for a long time like this.

While you might get used to it, this issue will start causing other components in the gearbox to fail and what might have been a salvageable component, will turn into something that's good for the bin.

How to fix the issue?

Unfortunately, there's no other way to put this. Replacing worn synchros will require taking the gearbox out of your car and taking it apart. This is something that requires some skill, especially when it comes to replacing damaged gears since there's little to no room for error.

The good news is that if you have only one faulty synchro, you can replace it without replacing the others, but the bad news is that, while it will save you some money, the fix still isn't going to be cheap. Another thing that you should consider is that the other synchros might soon fail as well, which would mean removing and taking apart the gearbox again, so another expensive repair is on the list.

The safest way would be to replace all synchros at once so that you know there's no need to constantly worry that the others will fail. Fortunately, there are many gearbox specialists out there and you shouldn't have problems finding someone to fix your issue.

Another tip to save some money would be to remove the gearbox yourself if you have the tools and experience necessary for this operation, and just take it to the shop that's going to perform the repair on it. Of course, there's always the alternative of using a used gearbox, but we think this is only a good choice if you are able to install it yourself and if it is very cheap since you don't know how the car it has been taken out of was previously driven.

A new gearbox will probably be very expensive, regardless of the make and model of your car, so save this as your last option and only take it into account if the synchro repair (which might also include other damaged components) is almost as expensive as a brand new gearbox.

How to avoid damaging synchros?

Avoiding damaged synchros is quite easy, and most drivers out there should have no problem following these simple steps.

Good shifting technique - Mechanical sympathy is the key here, so please don't be very aggressive when changing gears, even if you're on the track, as there is no need to do so. When you put into balance the time you save by doing this and the cost of repairing bad synchros, you will probably get to the conclusion that it's simply not worth it.

Also, don't rest your hand on the gear lever or the clutch pedal, as this will cause wear with time, even if it might seem harmless for the gearbox or clutch.

Change the gearbox oil regularly - While most gearboxes might have stickers on them that say the oil in them is Lifetime Oil, this refers to the lifetime of the car, which might be anywhere between 8 and 12 years, depending on the manufacturer.

Ask a transmission expert what would be the best service interval for your gearbox and what kind of oil to use to preserve it.

Inspect your gearbox from time to time - Strange noises? Difficult shifting? Take your car to a shop that specializes in transmissions. As you know, preventing issues is the best way to save money when maintaining a vehicle, so it's a good idea to have your gearbox inspected from time to time, as a simple repair now might prevent a painful bill later.

Final thoughts

Manual transmissions are fantastic when it comes to driver engagement and they are also a lot cheaper to repair than automatic gearboxes, but if you ignore symptoms that might appear harmless at first, you might end up with huge repair bills later, so always take your car to your local shop if you think something's wrong with it. And, for the last time, please, don't be so aggressive when shifting gears.