Sooner or later, you are going to face some issues with your gearbox. Shudder, inefficient temperature distribution, rough shifting, and other similar problems should be dealt with as soon as possible: Having a smooth transmission is not only convenient, important, and unobtrusive, but also safe for the car and, most importantly, you.
Table of Contents
Best Transmission Additives of 2024
| Image | Model | Type | My rating | |
|---|---|---|---|---|
 | Prolong PSL15000 Editor's Choice  | Automatic and Manual Transmissions | 9.8 | Check Price |
 | Lubegard 19610 Dr. Tranny | Eliminate Shudder | 9.7 | Check Price |
 | Lucas LUC10009 | Fix Slipping Transmission | 9.6 | Check Price |
 | Lubegard 60902 | Heat Reduction | 9.5 | Check Price |
Thankfully, you don’t always need to spend money on replacing the transmission, which can cost hundreds of dollars. Many people aren’t ready or able to pay such amounts whenever needed. Instead of replacing the gearbox, though, you could go the much easier and affordable route and buy a transmission additive.
Transmission additives aren’t your ultimate car savers since some vehicles may need a complete transmission replacement. But in most cases, additives should be enough. If a transmission additive sounds like a thing you may need, then our reviews of best brands will surely be of great interest to you!
1. Prolong PSL15000 – Best for Automatic and Manual Transmissions
Prolong Super Lubricants PSL15000 additive definitely does work with both automatic and manual transmissions. It still isn’t formulated for CVT gearboxes though, but fortunately, not many cars have that type.
This additive works by producing molecules that interact with metal surfaces, creating a protective layer to reduce friction and heat within the transmission. Overall, this additive should be able to smooth out manual shifters and make automatic transmissions more responsive.
Packing 8 ounces of additive, this product is pretty pricey, so getting a few packs could cost you quite a bit. However, if you choose this additive, it should deliver great results.
Pros:
- Treats both automatic and manual transmissions
- Protective layer reduces friction and heat
Cons:
- A bit pricey
2. Lubegard 19610 Dr. Tranny – Best to Fix Shudder
If you have shuddering issues with your automatic transmission, then Lubegard Dr. Tranny Instant Shudder Fixx could be the right solution for you. This additive is specifically designed to eliminate torque converter lock-up shudder.
In addition, Lubegard says that the Shudder Fixx reduces wear by up to four times compared to regular ATF transmission additives. And, frankly, that’s the kind of performance you would expect from such a product due to its price: For about $10, you get only 2 ounces of the additive.
As an ATF additive, Shudder Fixx is formulated to work only with automatic transmissions. However, bear in mind that this additive isn’t designed to work with CVT transmissions, or with the gearbox of Ford Type F.
Pros:
- Specifically formulated to deal with shudder
- Reduces wear up to four times
Cons:
- Works with only automatic transmissions
- Only 2 ounces of additive in the package.
3. Lubegard 60902 – Best for Heat Reduction
This Lubegard transmission additive is more about heat protection, though it is also formulated to soften hard shifts and reduce shudder and chatter. This additive deals with transmission fluid foaming and oxidation, reducing wear and elevated temperatures. If you have issues with cooling in your gearbox, you may want to take a good look at Lubegard 60902Automatic Transmission Fluid Protectant.
As is clear from the product’s name, this Lubegard additive is designed for automatic transmissions. Like the Shudder Fixx, though, it shouldn’t be used with Ford Type F and CVT transmissions.
Pros:
- Increases the fluid’s heat transmission
- Prevents overheating and reduces wear
Cons:
- Works with automatic transmissions only
4. Lucas LUC10009 – Best Transmission Additive for the Money
Lucas Transmission Fix is a highly praised transmission additive for its good balance between price and performance. Aside from that, at a very attractive price, you receive 24 ounces of the additive.
The Lucas Transmission Fix is also formulated to reduce the operating temperature and stop foaming, so it could be more appealing to you than Lubegard’s Transmission Fluid Protectant due to the price. Help to fix a slipping transmission problem.
However, expect it not to perform as well as Lubegard’s solution.
“Compatible with all transmissions and transmission fluids with the exception of CVT transmission and transmission fluids.” – Lucas Oil
How to Fix a Slipping Transmission
Pros:
- Eliminates Slipping
- Great value for the money
- 24 ounces of the additive in the bottle
5. Sea Foam TT-16 Trans Tune – Best for Complex Car Care
Sea Foam TT-16 is a bit more than a mere transmission additive. This product is also formulated to work with hydraulic and power steering systems, which could allow you to treat other problems your car might have. Unfortunately, owners of cars with manual gearboxes won’t be able to it.
The Trans Tune Transmission Additive could be a good option if excess moisture is an issue for you, since this additive is formulated to remove that. Aside from that, it is created to reduce rough or erratic shifting without altering the viscosity of your car’s transmission fluid.
Pros:
- Can be used in hydraulic and power steering systems
- Doesn’t change the viscosity of the transmission fluid
Cons:
- Doesn’t work with manual transmissions
6. Hot Shot’s Secret HSSTSE32Z – Best to Fix Transmission Hard Shifting
If you have a diesel engine and can’t really find a suitable transmission additive, then Hot Shot’s Secret Transmission Stiction Eliminator will probably interest you: It can be used with both diesel and gas automatic transmissions.
This product is meant to magnetically bond the metal components inside the transmission in order to reduce friction and wear. This should improve shifting almost immediately, so you may want to give this additive a try if you don’t have much time to spare.
Pros:
- Eliminates stiction
- Can be used in both diesel and gas automatic transmissions
- Comes in a large bottle
- Quick results
Cons:
- Works with automatic transmissions only
7. Bar’s Leaks Transmission Repair
Bar’s Leaks Transmission Repair is formulated to both improve shifting and protect the gearbox. This additive actually includes two solutions: After pouring them into the transmission, you should expect reduced noise, no leaks, no slipping, and no lazy shifts. Aside from that, the additive should help take care of the seals and O-rings in your automatic transmission. Bar’s Transmission Repair should reduce friction and heat, as well as stabilizing the fluid, thereby helping protect your transmission.
Bar’s is an interesting option if you want more of a complex solution for your automatic gearbox. The price of this additive is also a good advantage. Just bear in mind that this additive is only designed for automatic transmissions.
Pros:
- Attractive price
- Stops rough shifting and adds protection
Cons:
- Only for automatic transmissions
8. Liqui Moly 20040 ATF Additive – Best for Noise Reduction
Aside from putting the transmission back on track, Liqui Moly ATF Additive could also help you improve the power steering of your vehicle. If you have some issues with both the steering and transmission, this additive could be the best choice for you. All in all, what this additive should do is regenerate and clean the seals in power-steering systems and transmissions, damp down the shifting, in addition to protecting the components.
Unlike the transmission additive products we reviewed previously, Liqui Moly ATF Additive is more of a paste than liquid. This fact makes this product a bit easier to use, by not creating any mixing issues.
As you would expect, the ATF Additive is formulated for automatic transmissions only, so keep that in mind.
Pros:
- Improves power steering and transmission and reduces noise
- Adds protection to the transmission
Cons:
- Not for manual transmissions
9. XADO Atomic Metal Conditioner Maximum
XADO Atomic Metal Conditioner Maximum for automatic transmissions differs from the other additives we reviewed quite a bit. The very first difference that catches the eye is the fact that it comes in a syringe. Using the additive with a syringe should be much more convenient and easy than using bottled additives. However, a noticeable downside of the syringe package is that it doesn’t hold as much additive: The Atomic Metal Conditioner Maximum holds only 1 ounce of additive.
This product is fairly expensive as well. Given that, you should expect pretty good performance from the Atomic Conditioner. All in all, it is formulated to restore surfaces and protect them from friction and wear, which should both increase the performance and also increase the lifespan of the gearbox.
And, yeah, as you probably guessed, this additive works with automatic transmissions only.
Pros:
- Easy-to-apply
- Protects from friction and wear
- Eliminates surface defects
Cons:
- Expensive
- Includes only 1 oz. of additive
- For automatic transmissions only
10. zMax 51-306 – Best Inexpensive Transmission Additive
If you are looking for a transmission additive that costs as little as possible, then zMax’s Transmission Formula may be the right pick for you. It is the most inexpensive additive on our list. It contains just 6 ounces of the stuff, which isn’t that much, to be fair. Because of that, zMax Transmission Formula isn’t too cost-efficient, though it should work pretty well.
This formula delivers improved shifting performance and reduced wear on the vital parts of the transmission. It isn’t really clear which transmission types the Transmission Formula works with, but zMax clearly says that it isn’t for CVT transmissions. It seems, though, that buyers successfully used it with both manual and automatic transmissions.
Pros:
- Affordable
- Reduces wear and improves shifting
Cons:
- Not very clear which transmissions it can be used with