Best Transmission Additives: Restore Your Transmission’s Health for Smoother Performance

Unfortunately, we're all guilty of letting the health of transmission fluid slip our minds and failing to change it or top it off when necessary. When this happens, issues can persist or arise long before service intervals come up. While there's certainly no replacement for a proper fix, transmission additives can help you're transmission stay in the fight until you're ready to take it to the shop. Thankfully, there's no shortage of options to chose from. We have the best transmission additives available right here, along with a guide to help you find the right fit for your vehicle.

To select these products, we weighed how price, benefits, and application came together for each and denoted as necessary. If a transmission additive has few benefits but commands a reasonable price, it's not necessarily a bad product. On the other hand, if a product is on the more expensive side and also has few benefits (especially in user review form), then that's not as ideal.

We also cover a wide variety of transmission additives, meaning ones that could either work in conventional, torque-converter automatic transmissions, manual transmissions, and CVTs (or all of the above). Then, whether the additive plays nice with conventional petroleum-based or synthetic transmission fluid.

For more info on our methodology, check this out.

Prolong Super Lubricants PSL15000 additive is one of the best and most popular transmission additives on the market. This option can be used for both manual and automatic transmission systems. Prolong Super Lubricant works by producing molecules that interact with metal surfaces. These molecules create a protective layer that reduces heat and friction within the transmission system.

The PSL15000 promotes smooth and responsive gear changes, and it is suitable for both high- and low-mileage vehicles. This additive’s formula includes AFMT that chemically bonds to the surfaces of your system, providing a protective layer that helps reduce wear and tear. This single 8-ounce bottle of Prolong Super Lubricants Transmission Additive is enough for most transmissions.

A drawback to this product is that it has not been designed to work with CVT transmissions. Many users also report that this product also doesn’t work as efficiently with high-mileage SUV and trucks, but that may be linked to excessive wear that no additive can fix.

The Lucas LUC10009 transmission additive offers amazing performance and is highly recommended for transmission problems, such as slipping transmission, leakages, and hard shifting issues. It offers the perfect balance between price and performance. It is a solvent-free formula that has been designed to prevent foaming. It also helps lower the operating temperature of the fluid, stopping seal leaks. You can use this formula to revitalize old or worn-out transmission fluid—there is no need for draining. The Lucas Super Lubricants LUC10009 comes in a 24-ounce bottle and can be used for multiple treatments.

The greatest benefit users can get is it forms a polymeric film that works by renewing worn bands that help prevent transmission slippage. This process prevents overheating, renewing fluid that becomes worn due to heavy hauling.

One downside is this transmission additive is that it tends to change the way fluid levels react with heat, with users reporting having to drain fluid because the levels were too high once the transmission was hot, despite levels being perfect when cold. Also, these bottles are notoriously difficult to work with, even with a built-in funnel.

Hot Shot’s Secret HSSTSE32Z is among one of the most well-rounded options for automatic transmissions. It is an ideal transmission additive if you are looking to soften up your shifts, create a smoother ride, and protect your transmission on almost any vehicle.

The HSSTSE32Z helps lower ATF temperatures, reduces friction, and eliminates rust and corrosion, improving the overall performance of your automatic transmission system. A bonus with Hot Shot’s Secret Transmission Additive is it also works with CVT transmissions. It is a high-formulation lubricant with a unique composition capable of pulling deposits from coated areas.

A big drawback to the Hot Shot’s Secret HSSTSE32Z is that it can't be used for manuals. It’s also pricey compared to other transmission additives. However, you get more benefit from its 32-ounce bottle than most.

Lubegard offers a budget-friendly and reliable product you can use along with automatic transmission fluids. It's a rather efficient product that reduces friction and protects metal parts and internal components from damage. Furthermore, the additive works to prevent overheating without damaging the transmission system.

Thanks to the Synergol TMS Technology, the additive eliminates shudder and noises, making your rides more enjoyable. Another great thing about this additive is the ability to protect, condition, and restore seals and O-rings. It also prolongs the need to change the transmission fluid, which is rather convenient. For all the mentioned reasons, the Lubegard ATF protectant is one of the favorite choices among mechanics and drivers.

Despite the claims of universality, though, the additive won't work on just any type of vehicle. It's not recommended for CVT transmissions that most new cars and old some Fords have. To make sure the product will work on your system, you have to go to the company's website and check out the provided comparison chart.

Lubegard's Instant Shudder Fix is formulated to reduce and eliminate shudder, but it also works to resolve other transmission issues. Along with fixing the noise that makes rides uncomfortable, the additive makes fluids work for longer and enhances their overall performance.

The reason why both DIYers and professional mechanics opt for this product is the overall versatility and convenience. The additive is compatible with all synthetic automatic transmission fluids and proves to be rather efficient. The application is simple, and the product comes at a reasonable price. Therefore, drivers can protect, maintain, and repair the transmission system without much effort at all.

The bottle design is a little awkward, though. It's difficult to handle and might be challenging to pour the liquid from it. Still, the bigger issue regards the somewhat inconsistency the product might show over time. Many users report that it doesn't always reduce chatter and noise to desired levels.

This Lubegard product is ideal for those who are searching for CVT transmission additives. It's reliable, efficient, and budget-friendly. With just one application, the additive makes a huge difference in the transmission. From repairing damage to preventing it, the Lubegard additive works on all kinds of issues.

This particular additive doesn't only reduce noise and shudders. It also protects engine belts, pulleys, and other components. It will help you prevent premature wear of internal parts and damages caused by degraded fluid. In general, it will enhance the performance of your vehicle, making rides more comfortable and quiet.

There are only two minor drawbacks to keep in mind before the purchase. Firstly, the product doesn't always completely reduce the noise. It makes shifting incredibly smooth, but some shudder might remain even after the application. Secondly, you might have to wait for the additive to show results, although this mostly depends on the vehicle model.

Looking for a transmission additive that can do it all? You’ll love the Sea Foam TT-16 Trans Tune Transmission Additive. Designed to fine-tune your transmission, its fluid, and its overall performance, incorporating this under the hood can help round out your vehicle’s on-road results. And you may even be able to avoid future issues.

Sold in a 16-ounce aerosol can, Sea Foam’s additive features a petroleum base and three different oils, all blended together to clean deposits throughout your transmission and its related systems. It can be used in all petroleum and synthetic hydraulic fluids—which means it’s safe for just about any automatic transmissions. Once applied, this additive can help reduce rough, erratic shifting, eliminate contamination, and clean up your transmission overall.

The only real drawback is the price. This is more expensive than most of the other options. It also comes in a can that can see some major improvements in terms of delivery.

If you drive an older car with many, many miles on its odometer, you’ll want to consider K & W Chemical Trans-X High Mileage Automatic Transmission Treatment. This transmission additive is specially formulated and developed for cars with at least 75,000 miles, and it’ll work on much higher mileages, too. Each 16-ounce container of this additive can extend the lifespan of your current transmission, helping you to avoid common problems that can come with a whole lot of driving.

Made with a high-tech formula that’s designed to protect and bolster your transmission, this additive can stop or prevent leaks. It’s also a great option if you’re noticing less-than-smooth shifting; it can bring back the smoothness your vehicle once delivered. And adding this into your transmission fluid’s mix can also help replace any depleted ingredients it might’ve lost over time.

However, you’ll want to keep in mind that this additive is best used if you’re just starting to experience transmission issues like slips and shudders. It won’t be nearly as effective if you’re already seeing persistent problems.

Prolong Super Lubricants PSL15000 Transmission Treatment is an easy winner of our top pick. It's just a quality additive that delivers the results most car owners are after when their transmissions start acting up. However, the same can be said about our value pick, the Lucas LUC10009 Transmission Fix, which comes from an industry titan that specializes in this type of product.