Limitations of the GM 4L60 series OE input housing are the root cause of 3-4 burnup in performance applications. The weak OE backing plate flexes during clutch apply, allowing heat to build up unevenly within the clutch pack’s limited space. Stop the flex and you stop 3-4 clutch failure.

Sonnax Smart-Tech input housing kit 77733-12KB makes room for a taller clutch pack anchored in place by a stronger backing plate — the most reliable way to increase clutch capacity and protect against destructive heat.

To avoid the problems found with older, OE housing designs, Sonnax starts with the latest production, new housings from GM. These improved housings have splines for the input shaft that are cut at minimum spec for reliable shaft retention and sealing. The housings also benefit from added material for a thicker, more consistent cross-section that protects against breakage.

Smart-Tech input housing kit with heavy duty input shaft 77733-12KB fits 300mm torque converter, reluctor-style units. The shaft is manufactured from 300M ultra high-strength steel for exceptional toughness and resistance to fracture. It features a revised turbine end spline without an undercut where OE shafts commonly break. Both the housing and shaft also are available separately.

• Physically larger clutch pack area for increased 3-4 clutch capacity without sacrificing clutch durability. Use your choice of:
  • Eight .067" frictions with seven .095" steels
  • Nine .062" frictions with eight .077" steels
• Anchored backing plate keeps clutches parallel to stop the flexing and distortion that leads to heat build-up
• 100% New housing optimizes input shaft fitment and is further upgraded for significantly more resistant to fatigue failure
• Steel reinforcement sleeve prevents breakage in the spline area
• Custom backing plate replaces OE retaining ring to eliminate risk of blowout
• High-strength 300M shaft