5 Of The Best Transmission Additives To Improve Performance (According To Drivers)

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Whether it's an automatic or manual, the transmission in your car is one of its most vital and complex elements. It should go without saying that taking good care of it is extremely important, as it's what determines how cleanly you can shift and stay in gears. There's absolutely no substitute for regular upkeep and maintenance visits on your transmission, but there is a little something you can do to bolster its health and effectiveness in small ways: transmission additives, a little something you can add in addition to your regular transmission fluid.

The automotive industry is home to a myriad of different additives and substances you can pour into your transmission to improve its overall functionality. These additives can help to preserve your transmission's general health, lessen dangerous symptoms like gear slipping, and fix annoying problems like loud shuddering. Again, these should not be used in lieu of proper maintenance visits, and you should consult both your owner's manual and a trusted mechanic before using any of them. If you're still pretty sure you want to use an additive, here are a few popular choices available on Amazon with significant backing from user reviews.

For more information on how we selected these products, check out our methodology at the bottom of the page.

If you're driving a particularly large vehicle like a commercial truck or RV, your transmission is even more important than usual. The transmission in large vehicles works even harder than those in regular cars, as it's working to support the weight of thousands of pounds. If you feel bad for it, the nicest thing you can do is give it a little extra help with Lucas Oil Transmission Fix, available on Amazon for $13.99.

While this additive is fine to use in regular cars, it really shines when used in heavy-duty vehicles. It cleans and lubricates sticking valves, helping your existing hard-working transmission fluid to work even harder, not to mention last longer. It doesn't have any solvents or corrosive chemicals; you can add it right into pretty much any other transmission fluid without needing to drain it out first, and the additive will prolong the fluid's life up to four times.

Lucas Oil's Transmission Fix has a 4.6 out of 5 rating based on 6,549 Amazon reviews, making it one of the site's top-rated additives. Multiple users report immediate effects after adding it to their transmission, such as improved performance and smoother shifting. Some users do note, though, that it is not an absolute fix for any transmission, especially those that are already severely weathered or aged.

The main reason you typically use a transmission additive is to improve your vehicle's overall performance. A happy transmission makes for happy driving, not to mention fewer trips to the garage for spontaneous repairs. If you want to both improve your transmission's work and shore it up against future wear and tear, the XADO Automatic Transmission Fix is a great way to do it. You can get it on Amazon for $19.90, and there's a separate version for manual transmissions available for around the same price.

This performance-minded additive is built for all kinds of automatic transmissions, from traditional ones to CVTs to semi-automatics, delivered into the transmission via a compact syringe. The metal ceramic treatment contained within helps to restore and protect a transmission's metal components, while the anti-friction modifier helps to file down errant bumps and divots to smooth out shifting ability. As an added perk, this helps to quiet down the transmission's operations, reducing noise and vibration.

The XADO Automatic Transmission Fix has received a 4.3 out of 5-star rating from 1,637 Amazon users, earning an Amazon's Choice badge. According to one user, this additive was solely responsible for fixing a nasty slipping problem in a 2006 Mitsubishi Lancer, with other users offering similar praises. More critical reviews note that despite its effectiveness, its lifespan does leave a bit to be desired, diminishing in effectiveness after around 10,000 miles.

Some additives don't always play nice with certain brands and varieties of transmission fluid, their particular cocktails of chemicals having strange or dangerous effects when combined with others. This is why, if you're looking for a good additive, it'd be ideal to get one that's designed to work with most other products on the market. Lubegard's Automatic Transmission Fluid Protectant is purported to have a universal fit, so that's a safe bet. You can get it on Amazon for $16.99.

This nice and simple additive is designed for use with just about all types of automatic transmission fluids, whether they're conventional, synthetic, or low-viscosity. Once added, it provides a bevy of benefits, including lowered operating temperatures, reduced friction and wear, powertrain loss reduction, and smoothing out rough shifts and slipping. It'll also help to prolong the life of your usual transmission fluid, as well as prevent fluid foaming and loosening up stuck valves.

The Lubegard Automatic Transmission Fluid Protectant has a 4.6 out of 5 Amazon user rating based on 2,255 reviews, with several users crediting it for immediately fixing both gear slipping and hard shifts in their transmissions. The only catch is that the additive can be a bit hit-or-miss, with some users reporting no particular effects in their transmissions.

One of the most unpleasant phenomena you can experience from a vehicle's transmission is sudden, loud shuddering. It's alarming, distracting on the road, and more often than not, a sign that something bad is going down in your transmission. If loud shuddering is the most pressing problem you're facing with your transmission, that's a job for Lubegard's Instant Shudder Fixx, available on Amazon for $9.45.

This professional-grade additive is formulated with the express purpose of putting an immediate stop to lock-up shudder in a transmission's torque converter. You can use it in most types of automatic transmission fluids; just empty the whole tube into your dipstick or filler tube, and it gets right to work, all while providing four times less wear than standalone automatic transmission fluids.

The Lubegard Instant Shudder Fixx has a 4.5 out of 5 user rating on Amazon, backed by an impressive 4,657 user reviews. While its only function is eliminating shudder, users generally agree it's quite good at that, not to mention very easy to use as it's a one-tube-per-use product. Unfortunately, some users say that the effects are strictly temporary, and may also require multiple tubes to show results.

As your car gets on in years, your transmission may start to gradually deteriorate. Little nicks may accumulate in the gears, burnt fluids can gum things up, and so on. All of this can lead to bad shifting and compounding wear and tear. If you want to restore your transmission to at least a semblance of what it once was, you might get something out of Hot Shot's Secret Shift Restore, available on Amazon for $29.99.

This additive is built for both automatic and CVT transmissions, using its formula to dissolve gunky substances accumulated within the gears, as well as clean valve bodies and shift actuators. In its place, a protective layer is left behind that shores the components of the transmission up against further contamination and corrosion. This all results in a quieter, smoother, and cooler operational environment, eliminating slippage and irritating noises.

Hot Shot's Secret Shift Restore has earned a 4.5 out of 5 user rating from 1,713 Amazon reviews. The majority of users claim the additive removed slippage and noises entirely, or at the very least, noticeably lessened their effects. However, a small minority of users claim that the additive actually made some problems worse, so you should consult with a mechanic before using this.

Before you put any kind of mysterious goop in your transmission, it would definitely be good to know it does what it says it does. This is why user feedback for transmission additives is vital.

In order to select the preceding additives, we focused on products available on Amazon with a user rating of at least 4 out of 5 stars. Additionally, to ensure those scores were properly weighted, we also stuck to products whose high scores were backed by at least 1,500 user reviews.