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6 Best Transmission Additives of 2023

​What happens when your automatic transmission starts shuddering or the changes feel harsh and uncomfortable? It could be an indication that your transmission is needing some serious attention, perhaps even a rebuild. But, before you take that decision, it’s worth trying an additive. These are 6 of the best transmission additives on the market right now.

​Just to be clear, a transmission additive isn’t going to be a magic repair for mechanical problems​. They can’t repair metal and the like. But, under certain circumstances, they can make a huge difference in how your transmission works. They help to clear blocked oilways and sticking valves. A number of issues can be corrected with an additive.

​Types of Problems

​As we’ve already mentioned, an additive can’t cure all of your transmission woes. There is no way of repairing a mechanical fault (if something has broken or worn for example) without actually doing mechanical work. However, not all transmission problems are due to worn or broken parts.

​A great number of problems are related to the transmission fluid. The fact that it hasn’t been changed or that it’s left a varnish type substance behind that makes everything sticky. You may also find that as the fluid breaks down, it’s less able to cope with the demands placed on it. And of course, there’s moisture.

​One of the biggest problems with old fluid is that it foams up. So, instead of getting a smooth and consistent flow of fluid, it’s kind of like air, fluid, air, fluid.

​Leaking transmissions is also a thing, and some of these additives can ‘rejuvenate’ (read, soften) the seals inside the cases. In theory, it helps to retain the fluid from coming out of the main seal. It’s a temporary fix, but one that could last a few months or a few thousand miles.

​The Best Transmission Additives

Lucas LUC10009 ​Transmission Fix

Quick Specs
  • Rating: 4.9 / 5
  • Brand: Lucas Oil
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​This is the best additive for slipping transmissions. But, it does a whole lot more and can be used either as a preventative treatment or problem treatment. If there was a magic ‘cure-all’ for transmission woes, this would be on the list without a doubt.

​First up, they say it can be added to the existing fluid without having to drain any out. So, it’s easy. It will completely dry up most seal leaks. It also stops the fluid from foaming up.

On top of that, it lowers operating temperatures and most importantly, it helps to stop transmission slip, hesitation, and rough shifting. That is, if the problems are caused just by regular wear.

​Finally, they say it can be used in light-duty manual transmissions to make the gear changes a little more slick and smooth. However, it cannot be used for CVT systems. Personally, for such a great product, I can’t believe how inexpensive it is. It could be saving you a 1,000+ dollars transmission rebuild bill.

​This stuff, or a variant of it, has been around for years. It has never really lost popularity as one of the best additives to try in your transmission.

​The Sea Foam TT-16 is one of those products that has been developed to work in almost anything. It’s used for agricultural equipment, marine transmissions, industrial hydraulics, and power steering systems. It doesn’t matter whether the original fluid is petroleum or synthetic-based, this ​additive will just work.

​It doesn’t swell seals (or harm them in any way) and the three petroleum-based oils are blended to clean up varnish deposits. This should help to counter rough and erratic shifting and remove moisture. And it does so all without changing the viscosity of the original transmission fluid.

​If you’re looking to find a good quality, all-round transmission additive, this would work for you.

Liqui Moly 20040 ATF Additive

Quick Specs
  • Rating: 4.6 / 5
  • Brand: Liqui Moly
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​As this is an ATF additive, it’s suitable for power steering systems along with transmissions. It can be used as preventative care or trouble cure. When used as a preventative measure, it helps to protect from wear and lengthens the service life of the system – be that transmission or power steering.

​The Liqui Moly transmission additive has been formulated to regenerate oil seals and provide the optimum care for any rubber seal. This should help with oil loss. It also cleans & protects the inside of the transmission and components. This helps to dampen any noise and make the shifts just that little bit smoother.

​When used in a power steering system, it helps to improve the overall feel of the powered rack, making driving just that bit more comfortable & safe. This product works in any style of automatic transmissions.

​Just like the name says, the Lubegard 19610 has been designed to fix transmission shudder instantly. And in particularly serious cases, it’s been known to take 10 – 15 miles before it settles down. It’s so good that it has been voted a top product by a number of professional transmission techies.

​Basically, the marketing speak tells us that it’s a concentrate of ‘friction modifier’, specifically formulated to reduce the shudder felt when the torque converter locks up. It also has the benefit of giving four times less wear than regular fluid. However, it needs to be used as an additive, rather than a standalone product, so that’s not really relevant.

​The 2 oz. additive treats up to 10 quarts of tranny fluid. It can be used in pretty much anything aside from the Ford Type F, CVT transmissions, or anything with a dual-clutch.

​This is an anti-friction coating that sticks to metals to reduce friction. This, of course, reduces heat, and the extra lubricity means that shifts are smoother and quicker. It’s that simple.

​It can be used in both manual and automatic transmissions. When used in a manual it helps to make the shifting action smoother. And because of the slipperiness, it helps to bring back the responsiveness in an automatic transmission.

​If you want to get technical, the formula includes ‘Anti-Friction Metal Treatment Technology’ that chemically bonds to surfaces and provides a protective layer to stop wear.

​Everybody loves a secret right? It’s a bit like a secret sauce. Everyone wants to know what’s in it! Hot Shot’s make a big deal of ‘stiction’ – you know that moment when you’re trying to get something moving, and for a split second it ‘sticks’ before breaking free? That’s stiction.

​Their secret recipe additive reduces friction, lowers temperatures, eliminates rust and corrosion. It improves the overall performance of any automatic transmissions including CVT style transmissions. It’s a high-performance ester-based formulation, which has unique properties that ‘pull deposits’ from the coated areas.

​If you’re looking to soften up the shift of your vehicle, create a smoother ride and protect the transmission, the Hot Shot’s additive is the one you want. One person described it as “restoring the missing comfort”, and that says it all perfectly.

​Adding the Additive

​Some additives tell you to add it straight into the regular fluid without draining anything off. Others tell you to drain off the exact amount and refill with the additive. You need to pay attention to the instructions on the packet to see what you need to do.

​Here’s where it gets a bit tricky. Many auto transmissions have a dipstick to check the levels, while others rely on you removing a plug in the side casing of the tranny to measure the level. Open up the plug and fill it until the fluid starts leaking out (this is different from the fill & drain plug).

​If you need to do this, I’d recommend a quality set of jack stands to make it safe. And, of course, you’ll need a hydraulic jack or some other method of lifting the car. You also need to think about how you’ll remove the fluid if you’re just wanting to put some additive in there without doing a full fluid change. Dropping the drain plug from the transmission is a pain, and then you’ve got to try and replace it before too much fluid comes out.

​The easiest way to do this is with a fluid vacuum​. Not only can you see how much you’ve removed, but it’s also mess-free and quick. Simply slip a nylon or plastic tube down the dipstick tube and pump (well, vacuum) the fluid out – five minutes and you’re done. This of course also eliminates any need to get underneath the vehicle.

​Topping the system back up is easy – just use the dipstick tube again, and even if the additive is thick and hard to pour, you could always use the fluid vacuum in reverse to literally pump the fluid in.

​Different Systems

​Even though this is about the best transmission additives, it’s worth knowing that some of these additives can be used in other systems. They can be used either to help free them off, reduce friction, stop leaks, or reduce moisture. It’s the same as they do for transmissions, but in power steering systems, hydraulics, industrial, and agricultural hydraulics, marine transmissions – the list is large.

​A word of warning though, not all additives work in all systems. The Lucas additive, for example, is not to be used with CVT systems. So, before you buy anything, understand what it does, and what it can or can’t be used for. At best it may not work for you at all. At worst, it could make the problem a whole lot worse.

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