Popular Performance Parts

TH400 Forward Direct Clutch HD Aluminum Piston

TH400 4L80E 4L85E Reverse Servo Extendo Pin

SKU# T34913SERVO EXTENDO PIN Fits: GM 400 & 4L80E Extend your servo pin length in seconds!

GM Mechanical Modulator (Designed for TH400 Swaps from 700R4 on 6.2L Diesels)

SKU# 40MThe Fitzall Mechanical Modulator is designed to take the place of the vacuum modulator on all 700-R4 to 400 6.2L diesel switch-overs.

TH400 4L80E HD Low/Revers Servo Piston | Sonnax | Pre-1996

TH400 4L80E HD Low/Revers Servo Piston (95-Earlier) by Sonnax Heavy Duty Low/Reverse Servo PistonPart No. 34914-01 Fits all TH400 & '95-earlier 4L80-E. OE Part No. 24232745 OE cast aluminum servo pistons can be brittle and are prone to...

TH400 Externally Adjustable Low/Reverse Servo Kit | Sonnax

Designed for GM TH400 racing transmissions, Sonnax externally adjustable low/reverse servo kit 34914-20K makes band maintenance quick and easy. It’s an ideal way to improve reliability and make staging more consistent and predictable. Checking L/R...

TH400 Pump Thrust Bearing Kit | Sonnax

TH400 Pump Thrust Bearing Kit by Sonnax Part No. 34211-01K GM TH400 transmissions set front endplay with selective thrust washers between the pump and forward drum. In heavy-duty and racing applications, a common durability upgrade is to replace the...

4L80E 4L85E TH400 HD Intermediate Clutch Outer Sprag Race | Sonnax

4L80E 4L85E TH400 HD Intermediate Clutch Outer Sprag Race by Sonnax Part No. 34663HD-02 Improve GM 4L80-E, 4L85-E and TH400 transmission durability with Sonnax heavy duty intermediate clutch outer sprag race 34663HD-02. It’s an ideal upgrade...

TH400 Intermediate Pressure Plate Extra Heavy Duty Billet Steel

TH400 Intermediate Pressure Plate Extra Heavy Duty Billet Steel The extra heavy duty pressure plate provides superior strength and durability for drag racing and extreme off-road applications. Also available as a kit with matched sizes of 4 frictions, 4...

TH400 Reverse Cushion Kit (1965-1992) TransGo

TH400 Reverse Cushion KitFits all 400 1965-onDoes not fit 4L80E Corrects/Prevents/Reduces: Harsh reverse engagement Transmission removal is not required for this upgrade!

TH400 Transmission Stick Shift Reprogramming Kit (1965-1992) TransGo

Turbo 400 Transmission Reprogramming Kit™with Manual Shift ControlFits all 400 1965-on Features: Stick Shift, full manual control Full race; competition, off road and pro-street Converts back to automatic from the outside in 5 minutes Also...

TH400 Transmission Reprogramming Kit - TransGo

Features Automatic shift Street or full race Holds 1st and 2nd to any RPM Back-shifts to 2nd and 1st at any RPM Tow&Go™ or competition Also Includes (2) different size 1-2 shift valves Direct clutch high rate return springs Heavy duty...

TH400 Transmission Reprogramming Pro-Race Kit - TransGo

Features Automatic shift Street or full-race Holds 1st and 2nd to any RPM Back-shifts to 2nd and 1st at any RPM Tow&Go™, competition, pro-race, heavy duty, show-off Awesome capacity with adjustable shift timing and feel Also Includes (2)...

TH400 Line Pressure Booster Kit | Sonnax

Sonnax hydraulic line pressure booster kits contain stronger pressure regulator springs and large ratio boost valves designed to work together to provide progressive pressure increases as driving conditions become more demanding. Our pressure regulator...

TH400 Boost Valve Kit (No O-Rings Style) Sonnax

TH400 Boost Valve KitPart No. 34910-05K Factory Style, No O-Rings Vehicles with a THM 400 transmission frequently have poor line rise, soft 1-2 and/or 2-3 shifts,and/or Reverse engagement difficulties. These problems can be caused by the...

TH400 TH425 Boost Valve Kit | Sonnax | O-Ring Style

TH400 TH425 Boost Valve Kit | O-Ring Style Sonnax Part Number: 34910-01K NO TOOLING REQUIRED Vehicles with a GM TH400 and TH425 transmissions frequently have poor line rise, soft 1-2 and/or 2-3 shifts and/or Reverse engagement difficulties. These...

4L80E TH400 Heavy Duty Forward Clutch Hub | Sonnax

4L80E TH400 Heavy Duty Forward Clutch Hub NOT COMPATIBLE WITH 1964-1966 TH400 MAIN SHAFTS WITH MAJOR DIAMETER OF SPLINE ABOUT 0.980''. TO USE THE SONNAX HUBS INT HESE EARLY UNITS A 1967-LATE MAIN SHAFT WITH MAJOR DIAMETER OF SPLINE ABOUT 0.970'' MUST BE...

4L80E TH400 HD Forward Clutch Hub Front Washer (Pack of 5) 0.078"

Pack of 5 Sonnax forward clutch hub front washer 34298-078 replaces the OE .063" thick washer between the forward clutch hub and the forward drum. It is .015" thicker than OE and is the optimal way to tighten front unit endplay in most common builds...

4L80E TH400 TH425 Extreme Duty Forward Clutch Hub Kit | Sonnax

4L80E TH400 TH425 Extreme Duty Forward Clutch Hub Kit NOT COMPATIBLE WITH 1964-1966 TH400 MAIN SHAFTS WITH MAJOR DIAMETER OF SPLINE ABOUT 0.980''. TO USE THE SONNAX HUBS IN THESE EARLY UNITS A 1967-LATER MAIN SHAFT WITH MAJOR DIAMETER OF SPLINE ABOUT ...

TH350 TH400 MT540 Powerglide HD Pump Bushing | Sonnax | Steel .615''

TH350 TH400 MT540 Powerglide HD Pump Bushing Sonnax Part Number: 34034T-01 OE PART NUMBER: 29511860 Worn babbit pump bushings in GM Powerglide, TH350, TH400 and Allison® AT-540 transmissions allow the converter hub and inner pump gear to move...