The 4L60E transmission has long been a mainstay in the General’s arsenal of transmissions. The descendent of the 700R4, the 4L60E trans has a long history of backing up some fairly potent motors. In 1994, GM started using the 4L60E in all rear-wheel drive cars, until 2001 when performance demands had increased beyond its current capacity, and it was replaced with the 4L65E. The 4L65E was built on the same platform as the 60, but with a few differences. The 4L60E uses 4-pinion planetary carriers, these carriers are rated to 360 ft. lbs of torque. The 4L65E utilizes 5-pinion planetaries, along with a hardened input shaft, that boosted torque capacity to 380 ft.lbs. The nice thing about all of this is that the 5-lug parts are easily swapped into the 4L60E, leaving you with the ability to upgrade your existing tranny without having to buy a new unit.
Replacing the planetary carriers requires a full teardown. If you have never done this before, this may not be the time to start. This is not the most difficult tranny to build but it is certainly not the easiest. And there are a few specialized tools needed to correctly complete the job. A Rear Clutch Spring Compressor, Universal Pump Remover, Front Pump Alignment Band, Turbine Shaft Installer, and a Teflon Stator Shaft Installer, are all needed to properly disassemble and reassemble the 4L60E transmission.
The 4L60E transmission is an electronically controlled unit, notated as such by the “E” after the name. In 1993, when the 4L60E was introduced, the 700R4 was renamed 4L60. This is important as while they share some parts, they are different transmissions. In 1995, GM converted the 4L60E converter lockup circuit to a Pulse Width Modulated circuit. This type of lockup circuit offers a smoother transition as it pulses the signal instead of all at once. A PWM-type tranny will be marked with “PWM” on the front of the pump. The important thing to remember here is that the tranny type, PWM or non-PWM, must match the computer in the car, otherwise it will not function properly.
Since the upgrade requires a complete teardown, a full rebuild, with a few extra performance pieces, is a good idea. There are a few areas that require special attention and are commonly overlooked. The Pump Pressure Relief is the #1 cause of failure after overhaul. It is very easy to forget this little ball and spring, but it tends to get gummy and starts sticking. Even a few miles down the road can cause a failure, because the converter can’t release its pressure, eventually leading to overheating.
For this rebuild, we used several kits. A Trans-Go reprogramming kit, a Sonnax Billet 4th-gear “Super Hold” Servo, a Raybestos Z-pack clutch kit, and Red Eagle Red-Oxide clutches. We cherry picked the clutch kit, using the Z-pack for the 3-4 gear clutches. These are specifically designed to not bow and have superior holding power. The Red-Oxide clutches have better hold for 1-2.
Another piece that is a must in any high-performance transmission, is a beefy sun shell gear. It is integral in 2nd and reverse application. The stock parts have a tendency to sheer off the gear at the neck in high-performance applications. The aftermarket responded with the “Beast” sun shell. This unit is made of overall thicker material and includes a new thrust washer.
Here is the meat of the conversion, the 5-pinion rear planetary. In high-performance applications, the rear planetary carrier carries all the stress. Upgrading to the 5-pinion unit offers the ability to hold much higher torque values. The 4L60E also uses a 4-pinion front planetary carrier, which is more expensive than the rear unit. Upgrading to the 5-pinion front carrier is advisable in towing applications and where horsepower numbers are above 500. Our ’96 Impala will be running right at or just over 500, so only the rear 5-pinion was upgraded.
The 3-4 gear clutches reside in the drum, this is where the Z-pack comes in. The clutches are stacked in this order- finger clutch, inside clutch, finger clutch, etc. The final clutch is the brown clutch. The clutches are correctly stacked when the brown clutch is even with snap-ring groove. Then the 5 anti-centrifugal rev springs are installed, then the pressure plate, and another snap-ring.
With the drum assembled, the outer surface needs to be cleaned. Using a 3M coarse surfacing pad, the entire outer surface is cleaned of any glazing. The drum must be flat and smooth, if the drum surface is concave, it should be replaced. For the drum band, it is suggested using a late-model high-intensity band over a wide band. The wide band has little more hold, but the high-intensity band grabs and releases faster, which is more important in a high-performance application. The wide band is better suited for towing or in cases where the drum is worn in the center and replacement is cost prohibitive.
The Sonnax “Super Hold” billet servo can be installed with the trans in the car. This unique piece offers 40% more surface area for better holding power in 4th gear. This helps eliminate band failure in high-performance applications. It is simple to install, only a set of snap ring pliers is required. Just be sure to use the supplied steel washer. There is some adjustment to be made here though. The typical travel of the servo pin is .125”, if it is greater than that, the pin should be changed or carefully ground down to achieve the desired travel.
The valve body is an important step in modifying the 4L60E for performance applications. The Trans-Go reprogramming kit comes with everything needed to fix the valve body and make it suitable for high-horsepower. Before the valve body can be bolted on, the separator plate needs to be modified.
The separator plate rests between the transmission case and the valve body. It is a thin piece of die-cut sheet metal with 50 or 60 holes in it. Using the illustration in the reprogramming kit’s instruction, there are 10 holes that require drilling. These are the pressure apply and relief ports. Opening these up to .093” increases shift firmness and adjusts the timing of each shift. Not included in the kit instructions, we suggests drilling out the solenoid A and B ports to .040”. We found that this slightly increases shift time, which makes for a nice shift pattern on the street.
The 2nd accumulator body is modified with the springs supplied in the Trans-go kit. Using 2 springs gives the trans a very firm shift, using all 3 is for full-race applications only and will probably be too harsh for the street. We used 2 for the Impala.
The valve body itself gets a new spring and valve which modifies the isolator and converter regulator to allow the use of any type of torque converter lockup plate.
The total package, including labor, priced out at about $1300, not including the torque converter. We used an ATI High-stall Streetmaster lockup converter, which had a pretty hefty price tag at $640. All of the extra work we put into the transmission was well worth it. The Impala responds like it never has before and shifts nice and snappy under part throttle, but the full-throttle shifts are super sharp, and much better than the stock slush box.
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