The 10 Best Transmission Additives
This wiki has been updated 14 times since it was first published in March of 2018. Transmission health is crucial to any vehicle, but sometimes a complete flush can stir up small particles and endanger the finely-machined components. If your gearbox starts to whine, hesitate, or make clunking noises when shifting, or if you often tow heavy loads using a high-mileage drivetrain, one of these additives can protect and renew your high-mileage car or truck. When users buy our independently chosen editorial recommendations, we may earn commissions to help fund the Wiki.
February 04, 2021:
First and foremost, make sure you're getting an additive that is both safe for your transmission and appropriate for whatever specific issue you're having. Aside from that, we haven't made any major changes to this round of recommendations, because by and large, there haven't been any groundbreaking advancements in transmission fluid technology. Take Lucas Transmission Fix, for example, which has been around for a very, very long time and is still the standard by which many others are judged.
To reinforce the point that your use case is the most important factor here, there are also highly versatile options like Sea Foam Hydra Trans Tune that are good for refreshing seals in a range of high-pressure components. This, and others like Dr. Tranny's Kooler Kleen, aren't so much additives as they are treatments to be used during the flushing process - and that's something that only highly experienced individuals should undertake, due to the risk of stirring up sludge and unintentionally damaging your transmission.
August 20, 2019:
Along with the engine and brakes, a well-maintained transmission is one of the most vital aspects of keeping a vehicle in good working order. Unfortunately, it is also one of the most expensive components to fix, so rather than immediately running to the mechanic as soon as you notice a problem, consider trying one of these effective transmission additives first.
If you are experiencing slippage or hesitation during or after changing gears, we recommend you take a look at Lucas LUC10009, Prolong Super Lubricants PSL15000, and Liqui Moly 20040. All of these contain ingredients that can help make shifting smoother and restore some responsiveness. If your transmission isn't slipping, but rather just feeling very rough when shifting or shuddering periodically at slow-to-medium speeds, you'll want to look to LubeGuard Platinum and Dr. Tranny Instant Shudder Fixx.
Additives can do much more than simply make transmissions run smoother. For example, many of the formulas on our list recondition seals, however the best options for stopping minor leaks are Lucas LUC10009 and Liqui Moly 20040. If you need to rid your system of rust and minor surface damage on metal components within the transmission, Xado EX120 Revitalizant and Hot Shot's Secret Restore TSE can both help with that.
On another note, you shouldn't always wait until experiencing a problem with your transmission before reaching for an additive. Using Lucas ATF Conditioner with a good transmission fluid can go a long way towards preventing the formation of any problems in the future.
Molyslip G MTS If your car or truck has a hard time going in and out of gear, this may be your ticket to flywheel freedom. It's one of the few that's specifically intended for manual transmissions, and it reduces shifting time and effort effectively when performance is in demand. molyslip.com
Justice Brothers Automatic Transmission Conditioner Part of an extensive line of treatment products, this conditioner mitigates rough shifting in older SUVs, and it's often found at the racetrack, where it helps cut 1/4-mile times by limiting drag in the rear end. It mixes with all types of transmission fluids and grease, allowing for versatile use. justicebrothers.com