Sticking solenoids can cause harsh shifts, delayed engagement, and transmission warning lights. We researched and compared the top transmission additives designed to clean and lubricate solenoids, restore valve body function, and extend transmission life. Our evaluation is based on manufacturer specifications, published industry standards (such as ASTM for viscosity and friction modifiers), and aggregated owner feedback from thousands of real-world users. We do not claim hands-on lab testing; instead, we critically analyze each product’s chemistry, compatibility, and reported outcomes to help you choose the best additive for your specific transmission type and driving conditions.
| Photo | Product | Score | Buy |
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Lubegard 60902 Dr. Tranny Instant Shudder Fix Best Overall Lubegard 60902, 10 oz, compatible with most automatic transmissions and CVTs |
9.0 | 🛒 Check Price |
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Sea Foam SF-16 Trans Tune Best Value Sea Foam SF-16, 16 oz, safe for all automatic transmissions and power steering systems |
8.7 | 🛒 Check Price |
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ATP Automotive AT-205 Re-Seal Best for Leaks and Sticking ATP AT-205, 8 oz, compatible with all automatic transmission fluids |
8.4 | 🛒 Check Price |
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Lucas Oil 10013 Transmission Fix Best for High Mileage Lucas 10013, 24 oz, formulated for high-mileage automatic transmissions |
8.1 | 🛒 Check Price |
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BG Products BG 311 Super Clean II Professional Grade Cleaner BG 311, 11 oz, professional use, requires BG fluid exchange machine for best results |
7.8 | 🛒 Check Price |
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Rislone 4404 Hy-Per Lube Transmission Stop Slip Budget Pick Rislone 4404, 11 oz, compatible with most automatic transmissions except CVTs |
7.3 | 🛒 Check Price |
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Gunk 4-Cycle Power Steering and Transmission Stop Leak and Conditioner Multi-Use Conditioner Gunk M509, 12 oz, for automatic transmissions and power steering systems |
7.0 | 🛒 Check Price |
1. Lubegard 60902 Dr. Tranny Instant Shudder Fix: Best Overall
In our evaluation, Lubegard 60902 stands out for its patented Liquid Wax Ester chemistry, which is designed to clean varnish and deposits from solenoid valves without altering fluid viscosity. Owner feedback consistently reports resolution of shudder and delayed shifts within a short drive cycle. The additive is compatible with a wide range of transmission fluids, including CVT and dual-clutch, making it a versatile choice for most vehicles.
However, this product is not a fix for underlying mechanical damage such as worn clutches, broken springs, or electrical solenoid failures. If your transmission has hard metal-to-metal noise or complete loss of a gear, this additive will not restore function. It is best suited for early-stage sticking due to varnish buildup, not catastrophic failure.
- Contains Lubegard's patented Liquid Wax Ester technology that cleans and coats solenoids
- Stops shudder, rough shifts, and delayed engagement caused by sticking solenoids
- Safe for all automatic transmissions, CVTs, and dual-clutch systems
Pros: Works quickly, often within 50-100 miles; Does not over-thicken fluid, safe for high-mileage transmissions
Cons: Not effective for mechanical failures like worn clutches or broken springs
2. Sea Foam SF-16 Trans Tune: Best Value
Sea Foam Trans Tune is a well-known petroleum-based cleaner that targets varnish and sludge deposits. Based on owner feedback and spec sheets, it effectively restores solenoid function in many automatic transmissions, especially when used as part of a fluid flush. Its low cost makes it an attractive option for budget-conscious DIYers. We found it particularly effective for preventive maintenance in older vehicles.
However, it is not formulated for CVTs or dual-clutch transmissions, and some users report that it requires multiple treatments for heavily contaminated systems. If your transmission has severe sticking or metallic debris, this additive may not be sufficient. It is best for mild to moderate varnish buildup.
- Petroleum-based cleaner that dissolves varnish, gum, and sludge in solenoids and valve bodies
- Restores smooth shifting and reduces transmission noise
- Can be used as a flush additive or added directly to existing fluid
Pros: Very affordable per ounce compared to competitors; Works well as a preventive maintenance additive
Cons: May take longer to show results in severe cases; Not recommended for CVTs or dual-clutch transmissions
3. ATP Automotive AT-205 Re-Seal: Best for Leaks and Sticking
ATP AT-205 Re-Seal is unique because it conditions rubber seals to restore their flexibility, which can free sticking solenoids caused by seal swelling rather than varnish. Based on manufacturer specs and owner reviews, it is effective for transmissions with minor external leaks and intermittent solenoid sticking. It also contains anti-wear additives that protect internal components.
However, it is not a cleaner and will not remove existing varnish or sludge. Overuse can lead to over-swollen seals and new leaks. This product is best for transmissions where sticking is accompanied by seal leakage, not for heavy deposits.
- Conditioner that swells seals and O-rings to stop leaks and free sticking solenoids
- Restores hydraulic pressure for smoother shifts
- Includes anti-wear additives to protect transmission components
Pros: Dual-action: helps with both leaks and sticking solenoids; Works well on older transmissions with dried-out seals
Cons: Overuse can over-swelling seals, causing new leaks; Not a cleaner; does not dissolve varnish deposits
4. Lucas Oil 10013 Transmission Fix: Best for High Mileage
Lucas Transmission Fix is a popular choice for high-mileage vehicles. It works by increasing fluid viscosity, which can help solenoids maintain pressure and reduce slipping. Owner feedback often praises it for quieting noisy transmissions and improving shift quality in older cars. The large 24 oz bottle offers good value for the price.
However, thickening fluid can cause issues in transmissions designed for low-viscosity fluids, such as many modern automatics and CVTs. It does not clean solenoids, so sticking due to varnish may persist or worsen. This additive is best for older transmissions with worn seals and general sloppiness, not for precise solenoid cleaning.
- Viscosity improver that thickens fluid to reduce slipping and improve solenoid operation
- Contains anti-wear and anti-foam agents
- Designed to extend the life of high-mileage transmissions
Pros: Large bottle provides good value; Can reduce transmission noise and slipping
Cons: Thickens fluid, which may not be suitable for all transmissions; Not a cleaner; does not address varnish buildup
5. BG Products BG 311 Super Clean II: Professional Grade Cleaner
BG 311 Super Clean II is a professional-grade cleaner that is highly effective at removing heavy varnish and sludge from solenoids and valve bodies. Based on industry standards and tech reviews, it is one of the strongest cleaners available. It is often used in conjunction with a BG fluid exchange machine to ensure even distribution.
However, it is not easily available to consumers and typically must be purchased through a shop. The cost is higher than consumer products, and improper use can damage seals if left in too long. This product is best for severe sticking where other additives have failed, but it requires professional application.
- Highly concentrated detergent-based cleaner that dissolves heavy varnish and sludge
- Restores solenoid and valve body function in severe cases
- Often used by professional shops as part of a transmission service
Pros: Very effective on stubborn deposits; Trusted by many dealerships and independent shops
Cons: Expensive and hard to find for DIY users; May require a machine flush for proper distribution
6. Rislone 4404 Hy-Per Lube Transmission Stop Slip: Budget Pick
Rislone Hy-Per Lube Transmission Stop Slip is a budget-friendly option that includes seal conditioners and anti-wear agents. It is marketed to reduce slipping and improve shift quality. In our evaluation, it provided mixed results for solenoid sticking, with many owners reporting only temporary or partial improvement.
It does not contain strong detergents, so it is unlikely to clean heavily varnished solenoids. It may help if the sticking is due to minor seal swelling or friction, but for persistent solenoid issues, we recommend a dedicated cleaner. This product is best as a temporary band-aid or for very mild symptoms.
- Contains seal conditioners and anti-wear additives to reduce slipping and sticking
- Helps restore shift quality in older transmissions
- Budget-friendly price point
Pros: Very affordable; Can provide temporary relief for minor sticking
Cons: Not a dedicated cleaner; may not address varnish buildup; Some users report no improvement in solenoid issues
7. Gunk 4-Cycle Power Steering and Transmission Stop Leak and Conditioner: Multi-Use Conditioner
Gunk M509 is a multi-purpose conditioner designed for both transmissions and power steering. It works by softening seals to stop leaks and can free sticky solenoids if the sticking is seal-related. Owner feedback is mixed, with some finding it helpful for minor leaks but not for solenoid issues.
It lacks cleaning agents, so it will not remove varnish or sludge. Overuse can lead to seal damage. This product is best for transmissions with seal leakage and very mild solenoid sticking, but we recommend a dedicated cleaner for varnish-related problems.
- Conditioner that softens seals to stop leaks and free sticky solenoids
- Can be used in both transmission and power steering
- Includes anti-wear additives
Pros: Versatile for multiple systems; Low cost
Cons: Not a cleaner; does not remove deposits; May cause seal swelling if overused
Frequently Asked Questions
What causes transmission solenoids to stick?
Transmission solenoids stick primarily due to varnish and sludge buildup from degraded transmission fluid. Heat over time breaks down the fluid, leaving deposits that restrict solenoid movement. Other causes include contaminated fluid, worn seals, or debris from internal wear.
Can a transmission additive fix a stuck solenoid permanently?
It depends on the root cause. If the solenoid is sticking due to varnish or light sludge, a good cleaner additive can dissolve those deposits and restore function, often permanently if fluid is maintained. However, if the solenoid is physically damaged or has a broken spring, no additive will fix it; replacement is needed.
How do I choose the right additive for my transmission?
First, identify the symptoms: shudder, delayed shifts, or warning lights. Check your transmission type (automatic, CVT, dual-clutch) and fluid specifications. For varnish buildup, choose a cleaner like Lubegard or Sea Foam. For seal-related issues, a conditioner like ATP AT-205 may help. Always verify compatibility with your vehicle’s fluid type.
Are transmission additives safe for all vehicles?
Most additives are safe for conventional automatic transmissions, but not all are suitable for CVTs, dual-clutch, or continuously variable transmissions. Always read the label and check with your vehicle manufacturer. Overuse of viscosity modifiers can harm modern transmissions designed for low-viscosity fluid.
How long does it take for a transmission additive to work on sticking solenoids?
Many cleaners show improvement within 50 to 100 miles of driving, as the additive circulates and dissolves deposits. Some may require a full fluid flush or multiple treatments. Conditioners like re-sealers may work faster, often within a few heat cycles. If no improvement after 200 miles, the issue may be mechanical.
Our Verdict
After researching manufacturer specs, industry standards, and owner feedback, our top pick is Lubegard 60902 Dr. Tranny Instant Shudder Fix for its proven ability to clean and coat solenoids without altering fluid viscosity. For a budget-friendly alternative, Sea Foam SF-16 Trans Tune offers excellent value for mild varnish buildup. Always match the additive to your transmission type and symptom severity.
Last reviewed and spec-checked: August 3, 2025. We re-check our picks and listings periodically.
