Sonnax 
4L80-E transmission parts make it easy to add unmatched reliability to vehicles of any power level, from hardworking trucks to extreme street/strip race vehicles. Check out these handy Sonnax build guides to get maximum results out of your rebuild. Many parts listed here also fit 4L85-E and/or TH400 units.
- Heavy Duty Truck Basic Build
- High Performance Build (Under 1,000HP)
- High Performance Build (Over 1,000HP)
Heavy Duty Truck Basic Build
Pump/Valve Body
- Smart-Tech® Overrun Clutch Valve Kit [34200-40K] Details
- Lube Regulated Pressure Regulator Valve [34200-14K]*
- Line Pressure Booster Kit [4L80E-LB1]*
Internal
- Heavy Duty Forward Clutch Hub [34322-01]
- Heavy Duty Clutch Retaining Ring [28124]*
- Case Saver Retainer:
'98-Earlier [34762-10]
'99-Later [34762-20]*
Servo
- Adjustable Low/Reverse Servo Pin Kit '95-Earlier [34912-01K]
- Low/Reverse Servo Spacer Kit '96-Later [34528-01K]*
Case
- Heavy Duty Case Bushing Kit [34006-SPB]*
*For a more comprehensive build that maximizes transmission performance and durability, use Sonnax Performance Pack [HP-4L80E-01] in place of these components.
High Performance Build (Under 1,000HP)
Comprehensive Shift Upgrade Kit (Pump/Valve Body, Internal, Servo & Case)
- Performance Pack [HP-4L80E-01] Details
Pump/Valve Body
- Smart-Tech® Overrun Clutch Valve Kit [34200-40K] Details
Internal
- Heavy Duty Forward Clutch Hub [34322-01]
- Heavy Duty Input Shaft 300M Steel [34670-01]
- Heavy Duty Main Shaft 300M Steel [34672-01]
- Heavy Duty Intermediate Clutch Backing Plate:
'98-Earlier, .375" Thick [34144HD-01]
'99-Later, .275" Thick [34144HD-02]
Servo
Choose an all-in-one kit or individual components:
- All-in-one Kit: Externally Adjustable Low/Reverse Servo Kit [34914-28K]
- Adjustable Low/Reverse Servo Pin Kit '95-Earlier [34912-01K]
- Heavy Duty Low/Reverse Servo Piston:
'95-Earlier [34914-01]
'96-Later [34914-02]
High Performance Build (Over 1,000HP)
Comprehensive Shift Upgrade Kit (Pump/Valve Body, Internal, Servo & Case)
- Performance Pack [HP-4L80E-01] Details
Pump/Valve Body
- Smart-Tech® Overrun Clutch Valve Kit [34200-40K] Details
Internal
- Extreme Duty Forward Clutch Hub Kit [34322-02K]
- Extreme Duty Input Shaft Aermet Steel [34670-02]
- Extreme Duty Main Shaft Aermet Steel [34672-05]
- Heavy Duty Intermediate Clutch Backing Plate:
'98-Earlier, .375" Thick [34144HD-01]
'99-Later, .275" Thick [34144HD-02]
Servo
About the Performance Pack
The Sonnax 4L80-E, 4L85-E Performance Pack is the most complete upgrade kit for top-quality builds.
Innovative components work together to precisely recalibrate pressures and shift accumulation, delivering firmer shifts under load without sacrificing low-speed drivability
To target common wear areas in the transmission, the kit includes many improved parts to repair damage, prevent future wear and improve reliability
While many components also are sold separately (including those marked with a * on the heavy-duty truck basic build), some are available only in the Performance Pack.
About the Smart-Tech Overrun Clutch Valve Kit
See part details for important fitment and installation notes.
Insufficient holding power in the overdrive roller clutch is the underlying cause of chronic OD roller clutch failure in hardworking 4L80-E and 4L85-E transmissions. The patented Sonnax Smart-Tech overrun clutch valve kit improves OD roller clutch holding power in D4 and Reverse ranges to guard against failure and catastrophic transmission damage.
The Smart-Tech kit installs quickly onto the valve body — no transmission removal needed. It is also available pre-installed on a Sonnax heavy duty remanufactured valve body.
