4R70W/4R75W High Capacity Forward Clutch Drum Kit

Forward clutch durability is an issue in listed Ford performance applications. This problem often is addressed by eliminating the wave plate to fit more clutches, but plate removal creates harsh engagements and affects shift timing. Another common failure of stamped drums is cracking at the snap ring groove. The unique design of the Sonnax Smart-Tech high capacity forward clutch drum kit 76655-01K increases clutch capacity without abandoning the wave plate. The forged, one-piece drum prevents clutch drum breakage by eliminating weakness at critical stress points.

Increase Clutch Capacity, No Modifications Required
The physically larger clutch pack area in the Sonnax drum kit increases capacity by 20% when using six OE-thickness frictions and steels. Using OE-thickness steels maximizes heat dissipation to prevent burnt clutches.

Prevent Clutch Drum Breakage
The manufacturing process of the OE snap ring groove creates high-stress points around the circumference of the forward drum. The drum is active in 1st, 2nd and 3rd gear ranges and suffers the most abuse on a forced 4-3 kick down when it reapplies at higher pressure. The concurrent pressure from the forward clutch piston combined with the high stress at the snap ring groove causes the upper portion of the drum to split and separate at the groove. Depending on severity of the crack, this can result in no forward engagement or slipping in 1st, 2nd and 3rd gear. The one-piece, forged Sonnax drum kit is more durable than stamped drums and features increased groove depth for additional ring support. These are the same features found in the Smart-Tech standard capacity drum 76654-01K - watch this video for details.

• Increase clutch capacity by 20% without removing the wave plate
• One-piece, forged drum design prevents cracking