4L70E Shift Kit 1994, new and ready to install. Fits the 4L70E. Ships fast from the USA.
This is the Sonnax Performance Pack, part number HP-4L60E-01, a complete hydraulic recalibration kit for GM 4L60E, 4L65E and 4L70E transmissions from 1994 on. It is the kit to build into a Silverado, Sierra, Tahoe, Yukon, Suburban, Camaro or Corvette four-speed that tows, carries a modified engine, or keeps coming back with soft, slipping shifts and burnt clutches. Sonnax lists it as fitting '94-later units, so whether your truck calls its transmission a 4L60E, a 4L65E or a 4L70E, the same pack applies.
The factory calibration in this transmission family favors a soft shift, which means the clutches and the 2-4 band slip for a moment on every apply. That slip is heat, and heat is what burns a 3-4 clutch pack. The Performance Pack attacks it from five directions at once instead of just changing a spring or two. In the pump it adds a .490 inch boost valve with O-rings, an elevated pressure regulator spring and a high RPM pump slide spring, so line pressure rises faster and higher. In the valve body it adds a pinless forward accumulator, a 1-2 accumulator valve shim, eight checkballs and a drilling sequence for the separator plate. On the case side it adds a pinless 3-4 accumulator piston and spring plus a servo release check valve, and the servo gets new cushion and 4th return springs with fresh D-rings. A pinless 1-2 accumulator kit with a waved spring finishes it. Sonnax's point is that all of these work together, so the shift gets firmer under load without making low-speed driving harsh.
A shift kit firms up a healthy transmission; it does not repair one that has already burnt its clutches. If you have lost 3rd and 4th or the pan has friction material in it, that is a rebuild, and this pack goes in during it. Read any solenoid and pressure control codes before blaming hydraulics, because a weak EPC solenoid mimics low line pressure. Our 4L70E 3-4 clutch failure guide walks through what to check first, and 4L70E valve body testing covers the bore wear that a kit alone will not fix.
This listing is the 1994-later kit. The year matters in three places, and the Sonnax instructions call each one out:
If you are not sure which generation you have, send us the year and VIN before ordering. See every part we carry for this family on the 4L70E parts page, and our 4L60E, 4L65E and 4L70E interchange guide explains which internals swap between them.
Because the kit changes parts in the pump, case and servo as well as the valve body, it is a transmission-out job, best done during an overhaul. Follow the Sonnax instructions in order: inspect the TCC regulator bore first (vacuum testing is the reliable check, and a worn bore must be reamed and sleeved), drill the separator plate holes to the listed sizes, and plug the accumulator pin bores with the supplied steel balls. Lay old parts out in order as they come off. If the clutches are worn, pair it with the 1992-2003 Banner rebuild kit, and a fresh 1993-2005 solenoid kit removes the electrical variable. Refill with Dexron VI, check the level hot, and clear the adaptive shift values so the computer relearns the new pressures.
| Fits | 4L70E 1994 |
| Part type | Shift Kit |
| Condition | New |
| Brand | Sonnax |
| Ships | From the USA |
| Warranty | 1-year |
Doing this repair right usually means replacing these at the same time. Same transmission, ships together.
Yes. Sonnax builds the HP-4L60E-01 Performance Pack for 1994-later 4L60E, 4L65E and 4L70E units. The only year-specific steps are the boost sleeve spacer and the 1-2 accumulator spacer, both explained in the instructions.
Not completely. Sonnax states the pinless 1-2 accumulator kit must not be used with 1993 accumulator housings. For a 1993 unit, ask us before ordering.
No. The kit replaces parts in the front pump, including the boost valve and pump slide spring, so the transmission has to come out. Most builders install it during a rebuild.
Shifts will be noticeably firmer, especially under load, but Sonnax designed the spring and accumulator combination to keep low-speed drivability. It is aimed at towing, heavy-duty and performance use.
No, it is optional. It disables PWM/EC3 converter clutch slip control and is meant for converters with on/off friction material. Keep the stock calibration if your converter uses the factory-style slip friction.
Dexron VI ATF, which is GM's specification for this transmission family. Change the filter, check the level at operating temperature, and reset the adaptive values with a scan tool.
