10 Best Additive For Slipping Transmission 2025 in the United States

Lucas Oil 10009 Transmission Fix is a transmission additive aimed at helping vehicles with worn or slipping transmissions. It is designed to stop slipping, hesitation, and rough shifting by improving the transmission’s internal performance. One of its convenient features is that you can add it directly to your transmission fluid without draining the old fluid, which makes it simple to use. The product is compatible with many transmission types but is not recommended for CVT or dual-clutch transmissions, so it’s best suited for traditional automatic transmissions.

It contains seal conditioners that help stop common leaks by rejuvenating worn seals, which can save you from costly repairs. The additive also includes detergents that help keep the transmission clean from deposits. Packaged in bottles of 24 ounces (sold in packs of 12), it offers good value for regular maintenance or repair assistance.

This additive is geared towards older or worn transmissions rather than new or high-performance ones, and it won’t replace a fluid change or mechanical repairs if the transmission is severely damaged. If your vehicle’s transmission is slipping or shifting roughly and you want a relatively easy and affordable way to improve its operation, Lucas Oil Transmission Fix is a solid choice.

The Lubegard 61904 ATF Supplement is designed to improve automatic transmission fluid by adding strong friction modifiers, which help transmissions run more efficiently and at lower temperatures. It works by converting common ATF types like DEXRON II, III, and MERCON into a highly friction-modified fluid, which is particularly useful for addressing issues like clutch chatter and torque converter shudder. This makes shifting smoother and quicker, while reducing wear and extending fluid life by preventing foaming and oxidation.

It also assists in freeing stuck transmission parts and maintaining proper fluid viscosity, which are important for transmission health. The product is compatible with many transmissions, including certain Ford models known for shudder problems, making it a practical choice for those experiencing such issues. The additive requires some time to fully penetrate and show benefits, so effects may not be immediate.

While it substitutes premium dealer-brand fluids, it is sold as a supplement rather than a complete fluid replacement, so users need to add it to existing ATF. Its size and weight (5 gallons, about 39 pounds) make it better suited for professional or serious DIY use rather than casual topping-up. Users aiming to reduce transmission slipping, improve shifting, and protect their transmission may find this product very helpful, especially if they already use compatible fluids and require a friction-modifying boost.

Bar's Leaks 1414-5PK CVT Transmission Fix is a liquid additive designed to improve the performance and longevity of CVT transmissions. One of its strong points is the seal conditioner, which helps stop current leaks and prevents future ones by reconditioning the transmission seals—this can save costly repairs. It also contains anti-wear agents that improve metal-to-metal contact, which reduces slipping, jerking, and rough shifting, making driving smoother.

Another benefit is the inclusion of detergents and dispersants that clean sludge and varnish from the transmission parts, potentially extending the life of the fluid and components. The product also helps control fluid breakdown caused by heat, which reduces noise and wear. It is easy to use, with clear dosage instructions based on the transmission fluid capacity.

This product is specific to CVT transmissions and may not be suitable for other types of transmissions. While it can improve viscosity and friction properties, it is not a complete fluid replacement or a fix for severe mechanical issues. It comes in bottles treating up to 10 quarts of fluid, so for larger transmissions, multiple bottles are needed, which could add to the cost. Given its positive customer reviews and specialized formulation, this additive is a good choice for CVT owners looking to reduce slipping and extend transmission life through maintenance rather than repair.