The General's mainstay of transmissions was the used 4L60E transmission. The descendent of the 700R4, the 4L60E trans has a long history of backing up some potent motors. GM first began using 4L60E rear-wheel-drive cars in 1994. The demands for performance increased, as did the need for a new engine. The 4L65E was introduced. The platform was identical as the 60 and the 4L65E included a few changes. The 4L60E is powered with 4-pinion planetaries. They can generate an output of 360 ft. The 4L65E utilizes 5-pinion planetaries, along with a hardened input shaft which increased the performance to 38 ft.lbs. This makes the 4L65E an excellent option to upgrade your existing tranny.

A complete teardown is required for the replacement of the planetary carrier. If you've never attempted this before, this may not be the time to start. Although it's not the most challenging task but it's certainly not the easiest. There are several specialized tools needed to correctly complete the job. A Rear Clutch Springs Compressor, Universal Pump Remover, Front Pump Alignment Band, Turbine Shaft Installer and a Teflon Stator Shaft Installer are required to correctly take apart and rebuild the used 4L60E transmission.

The 4L60E transmission is an electronically controlled unit, identified with the "E" after the name. In 1993, after the 4L60E was launched the 700R4 model was changed to 4L60. It's important to know that although they share parts, they have different transmissions. GM modified the 4L60E lockup circuit into one that was Pulse Width Modulated in 1995. This kind of lockup circuit offers an easier transition since it pulses the signal instead of doing it all simultaneously. A PWM-type tranny will be identified with "PWM" on the front of the pump. One thing to be aware of in this case is that the tranny type, whether it is PWM or not is to match the computer used in the car or else it will not function properly.

To complete this project we utilized a variety of kits. An Trans-Go Reprogramming Kit, an Sonnax Billet 4th-gear "Super Hold" Servo, a Raybestos Z-pack clutch kit, and Red Eagle Red-Oxide clutches. The clutch kit was selected by cherry and the Z-pack was used for the clutches with 3-4 gears. These are specifically designed to not bow and have superior hold power. The Red-Oxide clutches have better hold for just 1-2.

Another component that is a must in any high-performance 4L60E transmission, is a robust sun-shell gear. It is an integral part of reverse and 2nd application. The stock parts tend to strip the gear at the neck in high-performance applications. The "Beast" sunshell was developed by an aftermarket. This unit is made of overall thicker material and includes a new thrust washer.

Valve Body

Modifying the 4L60E to run performance applications requires you to replace the valve body. The Trans-Go reprogramming kit comes with everything required to fix the valve and make it suitable for high-horsepower. Before the valve body can be bolted on the separator plate has to be changed.

The separator plate is situated between the transmission body and the valve body. It's a small sheet of metal cut by die with holes of 50 or 60 in it. Based on the diagram in the reprogramming kit's instruction, there are 10 holes that need drilling. These are relief ports and the pressure ports. Opening these up to .093" increases shift firmness and alters the time of each shift. We recommend drilling the ports of the solenoid B and A to.040 The drill is not included in the instructions for the kit. This can slightly extend the time of shift and results in more enjoyable to shift.

The valve body is upgraded with an upgraded spring and valve which modifies the isolator and converter regulator to permit the use of any type of torque converter lockup plate.