Earlier versions of this kit required an aluminum forward piston. It is recommended to follow the specific instructions provided during assembly to avoid a mismatch of parts.

4L60, 4L60-E

Smart-Tech® Input Housing Kit with Heavy Duty Input Shaft
Part No. 77733-10K

Fits '85-later 298mm units with 30-spline input shaft. For '82-84 298mm units with 27-spline input shaft, converter and stator shaft will need to be updated to '85-later design.

OE Part No. 17803689, 08663580

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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. The unique Sonnax Smart-Tech housing design makes room for a taller clutch pack anchored in place by a stronger backing plate, making it the only way to increase clutch capacity and protect against destructive heat. Numerous other improvements to the housing ensure maximum durability and protection against failure in higher horsepower, higher pressure applications.

Smart-Tech input housing kit with heavy duty input shaft 77733-10K fits 298mm torque converter units. The high-strength shaft features many unique refinements available only from Sonnax, including a unique design that protects against failure from stress cracks. 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
  • Treated housing is 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

Learn more about the Sonnax Smart-Tech Input Housing

Requires '91-later 3-4 apply ring; requires '87-later ring gear; requires '97-later stamped steel forward piston; requires '97-later dual-cage return spring; requires '87-later forward backing plate. Cannot be used with aluminum forward piston or Sonnax billet forward piston 77764-01. See instructions for further detail.

  • Smart-Tech® Input Housing with 298mm Input Shaft Assembly
  • PTFE Impregnated Rear Stator Support Bushing
  • Input Drum Reinforcement Sleeve installed
  • Overrun Piston Inner Seal
  • 3-4 Clutch Apply Plate
  • 3-4 Clutch Return Springs (10)
  • Bolt-on Anchor Plate
  • Overrun Piston Outer Seal
  • Socket Head Cap Screws (15)
  • Overrun Piston

  • 4L60, 4L60-E Smart-Tech® Input Housing Kit with Heavy Duty Input Shaft 77733-10K
  • 4L60, 4L60-E Smart-Tech® Input Housing Kit with Heavy Duty Input Shaft 77733-10K
  • 4L60, 4L60-E Smart-Tech® Input Housing Kit with Heavy Duty Input Shaft 77733-10K details


Harness that Horsepower! Your Guide to a Sonnax 4L60/E Level 3 Performance Build
Eliminate 3-4 Clutch Failure with the Smart-Tech® Input Housing

The Smart-Tech input housing kit is the best in the business. Have it in my 4L65E putting down over 700rwhp. Zero issues, no slippage and low temps. Sonnax parts are #1 in my book. 

N. Rodriguez
Koncept Motorwurks
Covina, CA