The 6 Best Transmission Additives Reviews 2019

​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, and 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 to how your transmission works – helping to clear blocked oilways, sticking valves … a number of issues can be corrected with an additive.

​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, but not all transmission problems are due to worn or broken parts.

​I’ve found that a great number of problems relate to the transmission fluid, and the fact that it hasn’t been changed, or that it’s left a varnish type substance behind which sticks everything up. 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 which in theory, 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

​1. Lucas LUC10009 ​Transmission Fix

Lucas LUC10009 24 Ounce Transmission Fix 24 Oz.

​Although I’ve put this as the best additive for slipping transmissions, being honest, this 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 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, stops the fluid from foaming up, lowers operating temperatures and most importantly, helps to stop transmission slip, hesitation and rough shifting … providing that 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, ​and cannot be used for CVT systems. Personally, for such a great product, I can’t believe how inexpensive it is … especially if it’s saving you a 1,000+ dollars transmission rebuild bill.

​2. Sea Foam TT-16 Trans Tune Transmission Additive

Sea Foam TT-16 Trans Tune Transmission Additive - 16 oz.

​This stuff, or a variant of it, has been around for years, and 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 – agricultural equipment, marine transmissions, industrial hydraulics, power steering systems, and 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, which should help to counter rough and erratic shifting and remove moisture, 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.

​3. Liqui Moly 20040 ATF Additive

Liqui Moly 20040 ATF Additive

​As this is an ATF additive, it’s suitable for power steering systems along with transmissions, and 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, which should help with oil loss. It also cleans & protects the inside of the transmission and components, which 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.

​4. Lubegard 19610 ​Instant Shudder Fixx​

Lubegard 19610 Dr. Tranny Instant Shudder Fixx, 2 oz.

​Just like the name says, t​he Lubegard 19610 has been designed to fix transmission shudder instantly, although in particularly serious cases, it’s been known to take 10 – 15 miles before it settles down. It’s that 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 the less wear than regular fluid, although it needs to be used as an additive, rather than a standalone product, so that’s not really relevant.

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

​5. Prolong Super Lubricants PSL15000 Transmission Treatment

Prolong Super Lubricants PSL15000 Transmission Treatment - 8 oz.

​The marketing for this trans treatment additive is trying to get all … science-y, and is using all manner of fancy words to give a simple message – it’s an anti-friction coating that sticks to metals to reduce friction, which 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 thanks to 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.

​6. Hot Shot's Secret HSSTSE32Z Transmission Restore Additive

Hot Shot's Secret HSSTSE32Z Transmission Restore Additive 32. Fluid_Ounces

​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 and improves overall performance of any automatic transmissions including CVT style transmissions. It’s a high-performance ester based formulation, which has unique properties that ‘pulls 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 straight in to the regular fluid without draining anything off, and 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 of the transmissions (auto) 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 jackstands 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.

​For me, I’ve found 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

​So although this is about the best transmission additives, it’s worth knowing that some of these additives can be used in other systems, either to help free them off, reduce friction, stop leaks, reduce moisture … 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 with – 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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