Failure of the intermediate stub shaft and direct drum are almost inevitable when listed Ford transmissions are pushed to the limit. To maximize durability and improve clutch capacity in heavy-duty/performance vehicles, Sonnax offers Smart-Tech direct clutch drum and shaft kit 76656-01K, the first upgrade to eliminate every critical weakness.

Most failures in these units occur where the direct drum and stub shaft connect. Even other aftermarket upgrades that rely on a heavy-duty shaft will sheer in this area under extreme conditions. Unlike those two-piece assemblies, the all-in-one Smart-Tech easily handles the highest horsepower/torque levels. The unique one-piece clutch drum with integrated stub shaft is precision machined from high-strength steel to guarantee there are no splines to strip from the drum or weaken the shaft. The shaft itself is significantly thicker and 2X stronger than the OE. Due to its larger diameter, the integrated shaft must be used with the kit’s custom, heavy-duty sun gear.

Insufficient holding power is another area 4R70-series transmissions fall short, but installing thinner aftermarket steels and backing plates to increase clutch capacity isn’t ideal. Those components increase clutch pack flex and heat build-up, making them the primary cause of repeat burn-up. To improve both performance and long-term reliability, the Smart-Tech’s custom drum and piston hold an OE backing plate and seven OE frictions for 17% more clutch capacity than the six-friction stack-up.

• One-piece design eliminates weak point where drum splines strip and shafts break
• Rugged shaft is 50% thicker and twice as strong as OE
• Custom drum and piston deliver 17% more clutch capacity with optimum protection against burn-up
• High-strength drum and shaft are precision-machined from hardened 8620 steel
• Unique sun gear is precision-machined from 9310, heat-treated steel