Learning Center

Best Torque Converter for Drag Racing
Boss Hog Learning Center The best drag racing converter is the one that helps the engine reach its useful power range, loads the drivetrain correctly, and delivers consistent launch performance for the specific car. Engine PowerbandConverter selection should complement where the engine produces torque and horsepower. Camshaft, displacement, compression, induction, and power adders all matter. Vehicle WeightA heavier car loads the converter differently than a lightweight race car. Weight is a major part of how the converter flashes. Rear Gear and Tire DiameterGearing and tire size determine mechanical leverage and... Read more...
Turbo LS Converter Guide
BOSS HOG LEARNING CENTER A turbo LS converter has to do more than hit a target stall RPM. It must help the engine reach the range where the turbo can respond while controlling heat, slip, and drivability for the way the vehicle is actually used. Turbo Size Changes Converter NeedsA larger turbo may require more engine speed and load before it responds strongly, while a smaller turbo may come on sooner. Converter characteristics should complement the turbo rather than work against it. Engine Displacement and TorqueA 4.8, 5.3, 6.0, and... Read more...
Towing Performance Guide
BOSS HOG LEARNING CENTER Good towing performance comes from the entire drivetrain working together. Engine torque, transmission gearing, converter behavior, axle ratio, tire diameter, cooling, and vehicle weight all matter. Know the LoadStart with trailer weight, cargo, passengers, terrain, and towing frequency. The more load the drivetrain sees, the more important gearing and heat management become. Watch Tire SizeLarger tires reduce effective gearing. A truck that towed well on stock tires may feel noticeably weaker after a large tire-size increase. Match Rear GearingAppropriate axle gearing helps the engine and transmission... Read more...
Torque Converter Troubleshooting Guide
BOSS HOG LEARNING CENTER Torque converter problems can feel like transmission problems, and transmission problems can feel like converter problems. The best diagnosis starts with the symptom, when it occurs, and what changed before it began. Common Torque Converter SymptomsCommon complaints include shudder, vibration, excessive heat, poor acceleration, inconsistent stall, delayed engagement, lockup problems, unusual noise, or engine RPM that rises without corresponding vehicle speed. Shudder or VibrationShudder can occur during lockup engagement, light-throttle cruising, or acceleration. Possible causes include converter clutch problems, contaminated fluid, driveline vibration, engine misfire, or... Read more...
Torque Converter Slippage Explained
BOSS HOG LEARNING CENTER Torque converter slip is one of the most misunderstood parts of an automatic transmission. Some slip is normal and necessary. Too much slip can create heat, reduce efficiency, hurt acceleration, and point to a converter or transmission problem. What Is Torque Converter Slippage?A torque converter transfers engine power to the transmission through fluid rather than a direct mechanical connection at all times. Because of that fluid coupling, engine speed and transmission input speed can differ. That difference is commonly described as converter slip. At low speed... Read more...
Stall Speed for Trucks
BOSS HOG LEARNING CENTER Truck stall speed should be chosen around the whole truck—not around a single RPM target. Weight, torque, gearing, tire diameter, towing, and modifications can all change what the converter needs to do. Why Trucks Are DifferentTrucks are generally heavier than performance cars and often use taller tires, tow loads, or see off-road duty. Those factors place different demands on the converter. Vehicle Weight and LoadA loaded truck can behave very differently than the same truck empty. If the vehicle tows or carries significant weight, include that... Read more...
How Converters Affect 60-Foot Times
BOSS HOG LEARNING CENTER The first 60 feet of a drag-strip pass is where torque converter selection can have a major influence. The converter affects how quickly the engine reaches its useful power range and how effectively that power is applied to the drivetrain. Why the First 60 Feet MatterA strong 60-foot time gives the vehicle momentum early in the run and can improve elapsed time throughout the pass. Converter behavior is one part of that launch equation. Too TightA converter that is too tight may load the engine below... Read more...
HEMI Stall Speed Guide
BOSS HOG LEARNING CENTER Choosing stall speed for a HEMI-powered vehicle requires more than picking a number from a chart. Engine torque, camshaft, transmission, vehicle weight, gearing, tire diameter, and intended use all influence the result. Why HEMI Torque MattersHEMI engines can produce strong torque, and that torque affects how a converter flashes. A converter that behaves one way behind a mild engine may act differently behind a higher-output HEMI. Camshaft Changes the PowerbandA larger cam can move the engine’s useful range upward and may require additional stall to avoid... Read more...
C4 Racing Converter Guide
BOSS HOG LEARNING CENTER The Ford C4 remains a popular racing transmission because of its compact size, efficiency, and broad aftermarket support. A racing C4 converter should be selected around the engine and chassis combination, not just an advertised stall RPM. Engine Powerband Comes FirstThe converter should help the engine reach the RPM range where it produces useful torque and horsepower. Camshaft, displacement, compression, induction, and power adders all matter. Vehicle WeightA heavy car and a lightweight race car can flash the same converter differently. Weight should always be part... Read more...
Bracket Racing Converter Guide
BOSS HOG LEARNING CENTER Bracket racing rewards consistency. The fastest converter is not always the best bracket-racing converter if it makes the car harder to repeat from pass to pass. Consistency Comes FirstA bracket car needs predictable launch behavior, repeatable engine response, and stable performance as track and weather conditions change. Match the Engine PowerbandThe converter should place the engine in a useful RPM range without making the combination unnecessarily loose. Vehicle Weight and GearingWeight, rear gear, tire diameter, and transmission ratio all affect how the converter behaves and how... Read more...
Best Torque Converter for LS Engines
Boss Hog Learning Center There is no single best torque converter for every LS engine. A stock 5.3 truck engine, cammed 6.0 street car, naturally aspirated 408 stroker, and turbo LS build can all require very different converter characteristics. Start With the Complete LS CombinationConverter selection should begin with displacement, camshaft, cylinder heads, intake, exhaust, power level, transmission, rear gear, tire diameter, vehicle weight, and intended use. Peak horsepower alone is not enough. Camshaft MattersMany LS builds receive a larger camshaft early in the modification process. A cam that moves... Read more...
Best Torque Converter for Towing
Boss Hog Learning Center The best towing converter is not necessarily the lowest-stall converter available. Towing places sustained load on the drivetrain, so converter selection should focus on torque, gearing, heat control, lockup behavior, and how the truck is actually used. Start With Towing WeightKnow the vehicle weight, trailer weight, cargo, and how often the truck tows. A lightly loaded weekend tow vehicle and a heavy-use tow rig have different demands. Engine Torque CurveA towing converter should complement where the engine makes useful torque. Diesel, big-block gasoline, and modified small-block... Read more...
Best Converter for Coyote Engines
Boss Hog Learning Center Ford Coyote engines make power differently than many traditional pushrod combinations, and the best converter depends on the complete package—not simply engine displacement or peak horsepower. Start With the Coyote PowerbandCoyote engines often make strong power at higher engine speed. Converter selection should complement the engine’s torque curve and the transmission gearing rather than relying on a generic stall recommendation. Transmission Choice MattersA Coyote behind a traditional automatic, overdrive automatic, or swapped transmission can require different converter characteristics. The converter needs to work with the transmission... Read more...
Best Converter for AOD
The Ford AOD is popular in classic Ford street and restomod builds because it adds overdrive without giving up automatic transmission convenience. The right converter should support acceleration, cruising, and the engine’s useful power range. Why AOD Converter Selection MattersThe AOD’s overdrive capability makes it attractive for street vehicles, but the converter still has to match the engine, vehicle weight, rear gearing, tire size, and intended use. Mild Street BuildsA mostly stock or mildly modified engine usually needs a different converter than a larger-cam street/strip combination. More stall is not... Read more...
Best Converter for 727
The Chrysler TorqueFlite 727 has been used in everything from classic Mopar muscle cars to trucks and dedicated race cars. The best converter depends on the engine, vehicle, gearing, tire size, and intended use. Street Mopar ApplicationsStreet cars benefit from a converter that improves response without creating unnecessary heat or poor cruising behavior. Camshaft and Engine TorqueA larger camshaft or higher-output engine can move the useful powerband and change the converter requirement. Big-Block and Small-Block DifferencesEngine displacement and torque output affect how the converter flashes and couples. Do not assume... Read more...
Best Converter for 4L80E 4L85E 4L90E
The 4L80E 4L85E 4L90E is a popular choice for high-torque street cars, trucks, LS swaps, towing builds, and boosted combinations. Its strength does not eliminate the need for a properly matched converter. Match the Converter to the 4L80E 4L85E 4L90E ApplicationEngine torque, camshaft, vehicle weight, rear gear, tire diameter, and intended use all matter. The same 4L80E can be used in vehicles with completely different converter needs. Street and Restomod BuildsA street-focused 4L80E 4L85E 4L90E combination should balance launch performance, cruising efficiency, lockup behavior, and heat control. Truck and Towing... Read more...
Best Converter for 4L60E 4L65E 4L70E 4L75E 300mm Converters
The best 4L60E torque converter depends on what the transmission is behind and how the vehicle is used. A stock truck, cammed street car, LS swap, and boosted build can all need different converter characteristics. Why the 4L60E 4L65E 4L70E 4L75E 300mm Combination MattersThe 4L60E offers overdrive and electronic control, but converter choice still has to match engine torque, camshaft, vehicle weight, rear gear, tire diameter, and intended use. Lockup Is Part of the DecisionA lockup converter can reduce cruising slip and heat when applied. For street vehicles, tuning and... Read more...
Best Converter for a Cammed LS
A big cam changes where your LS makes power — and that changes what your torque converter needs to do. Get the converter right and the car feels crisp and responsive; get it wrong and it feels lazy off idle or busy on the highway.Why a cam changes the converterAggressive cams move the torque curve up the RPM band and pull vacuum down at idle. A stock converter with a low stall speed will be "below the power" — the engine bogs off the line because it can't get into... Read more...
Signs of a Bad Torque Converter
A failing torque converter often shows up as a driveability problem that's easy to mistake for a broader transmission issue. Here are the most common warning signs — and what they usually mean.SlippingIf engine RPM climbs but the car doesn't accelerate like it should, the converter may be slipping. You'll usually notice it under load — going uphill, merging onto the highway, or towing.Shuddering at cruiseA shudder or vibration around 40–60 mph, especially as the lockup clutch engages, points to a worn clutch or contaminated fluid. It often feels like... Read more...
Lockup vs Non-Lockup
One of the first decisions in picking a converter is lockup vs non-lockup. Both can work for the same car — the right choice depends on how you drive it.Non-lockupA non-lockup converter always runs through the fluid coupling. It's simple, proven and common in older automatics and many race applications. The trade-off is that there's always a small amount of slip at cruise, which generates heat and costs a little fuel economy on the highway. Pros: simple, no electronics needed, easy to control in a race car. Cons: more slip... Read more...
How Torque Converters Work
A torque converter is the fluid coupling that sits between your engine and automatic transmission. It does two jobs: it lets the engine idle while the car sits still, and it multiplies torque when you launch. Here's how.The core parts Impeller (pump): bolted to the engine side, it flings transmission fluid outward as the engine spins. Turbine: connected to the transmission input, it catches that moving fluid and starts to turn. Stator: the piece in the middle that redirects fluid coming off the turbine back into the impeller — this... Read more...
What Stall Speed Do I Need?
"What stall speed do I need?" is the most common question we get — and the honest answer is that stall speed is never chosen in isolation. It's the result of your whole combination working together.What stall speed actually meansStall speed is the engine RPM at which your torque converter begins to efficiently transfer power to the transmission. Below that RPM the converter "slips" on purpose, letting the engine rev up; at stall it starts to couple and put the power to the ground. A higher-stall converter lets your engine... Read more...