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New Transmission Upgrade from Sonnax Takes On High Horsepower with Race-Ready Ratio

Confidently running big power through Ford automatics is the new reality for extreme racers on the street and strip. The Smart-Tech®direct clutch drum and shaft kit introduced last year by Sonnax is a critical upgrade for any driver pushing the limits of stock AODE, 4R70W components. By popular demand, this revolutionary kit is now available in two gear ratios: the original 2.84/1.55 and — new for 2020 — the numerically lower-ratio 2.40/1.46 ideal for higher power, dedicated racing vehicles.

While this family of transmissions can handle big power, the whole direct clutch area is major weakness because its design long ago fell behind advances in engine output. Smoked clutches are chronic due to insufficient torque capacity, and the fragile intermediate stub shaft is prone to shearing at the worst times. Aside from knowing that extra torque can quickly kill their transmission, many drivers never realize the exact nature of this ticking time bomb until they lose 3rd and 4th gears. In the past, they often learned even worse news: there was no way to guarantee it wouldn’t happen again. Builders struggled for years chasing direct drum failures because the right components just weren’t available to solve all of its design flaws.

Sonnax — the leader in transmission innovation — dug into the root cause of both intermediate stub shaft and direct clutch problems when developing the patented Smart-Tech kit. Its foundation is a unique, one-piece design that eliminates the weak connection point where drum splines strip and shafts break. Even other aftermarket upgrades that rely on a heavy-duty stub shaft will sheer in this area under extreme conditions. The Smart-Tech shaft itself is significantly thicker — two times stronger than the OE — and works with a unique, heavy-duty sun gear that installs over the top. To optimize protection against clutch burn-up, the custom drum and piston hold one extra friction for 17% more clutch capacity.

Two ratio options mean Sonnax has every vehicle covered. Part No. 76656-01K fits Ford 4R70E, 4R70W, 4R75E and 4R75W transmissions with 2.84/1.55 gear sets. The new kit, Part No. 76656-02K, fits Ford AODE units with 2.40/1.46 gear sets. The lower ratio helps keep performance engines in the optimal power band while allowing a longer pull in first and second gears, improving consistency and performance.

Visit for details on these and other Sonnax upgrades. Sonnax transmission parts are available from performance parts distributors and are the trusted choice of top performance specialists worldwide.

This story was originally published on May 5, 2020. Drag Illustrated

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