There was a time in the not so distant past that if you said “it’s an automatic” the competition began to salivate at picking on the wimpy kid in the schoolyard. Those days are long behind us as technology has advanced automatic transmissions to be a darn near equal rival to its manual gear-selecting brothers. It wasn’t always smooth going, especially for the readers who have experienced the venerable 700-R4 of the ’80s and early ’90s. That slushbox went through the digital age and an electronic version, known as the 4L60. The brass at General Motors had the 4L60 stuffed into a wide variety of vehicles beginning in 1993, and by the following year our beloved Corvette benefited from the four-speed, overdrive automatic transmission.
Just a few short years into its production run there was a running change to the 4L60, when it became known as the 4L60E, and saw a service life in the C4 model that carried over into the C5 edition, until it was phased out completely by the 2004 model year. With the 4L60E being accepted and utilized as a high-performance transmission solution, there comes the need for upgrades as some factory components that aren’t up to snuff. Enter PerformaBuilt Transmissions, a company dedicated to building high-performance transmissions, with the 4L60E being one of its specialties.
We followed along as the staff at PerformaBuilt massaged a 4L60E into a Level 2 Pro Race transmission that is capable of holding up to 700 hp. In the real world that is a hefty power number and the company backs its claim with a 1-year warranty. The next step up from the Level 2 Pro Race would be the Invincible series, capable of handling 850 rwhp, but that is reserved for the 1 percent group in this hobby. For most, the 700-rwhp version is plenty strong, and its price tag of $2,195 is moderate when compared to other options.
The kick-off actions for the rebuild begin with disassembly and cleaning. Once all the major components are stripped away, PerformaBuilt technicians then analyze the major components for fatigue, wear and any damage that could affect performance and durability. Once the bad parts are discarded and replaced, the bare 4L60E case gets coated with heat resistant, oil-based enamel. The heavy-duty coating is baked on and it gives the case a glossy finish that is highly durable.
Filling the transmission case is a mix of OEM and aftermarket upgrades and PerformaBuilt addresses several weak areas of the 4L60E. The technicians add the typical upgrades like better clutch packs and steels, of which PerformaBuilt sources from BorgWarner, Raybestos and Alto. The company also addresses several inherently weak components like the sun shell and drum. Each one of those components are replaced with a much more durable aftermarket solution that has been designed not for boring passenger car use but rather a life of high-performance action. Several stock parts are carried over but each one is cleaned and properly inspected to ensure proper performance and longevity.
During the rebuild process, PerformaBuilt’s Alan Pickering pointed out various tidbits about the 4L60E transmission. For example, the factory sun gear (not to be confused with the sun shell) is inspected and modified with four slots on the bottom. These machined slots allow oil to escape the bearing/gear assembly and add more lubrication to the planetary gears. Pickering said that one of the most common misconceptions about the 4L60E is a weak planetary gear, when, in fact, the problem stems from a lack of lubrication in high-performance applications. The modified sun gear helps remedy the problem, ensuring a long life for the planetary gears.
After the new sun shell is installed, dubbed the Beast, the front planetary gearset is also inspected and modified. Like the rear planetary, lack of lubrication is the source for almost every single high-performance failure in that component. That said, the front sun gear is machined to allow better flowing lubrication to help feed the planetary gears. Of course, the reassembly of the 4L60E is performed under the exact specs set forth by PerformaBuilt as the new aftermarket upgrades and modifications require the internals to be set up properly in order for it to function properly.
Modifying the valvebody is one of the last steps that PerformaBuilt tackles and the company has developed its own modifications after many years in the transmission business. According to Pickering, each shift kit on the market has unique features but you have to take the good with the bad with most of the over-the-counter kits. PerformaBuilt, however, utilizes elements from several different shift kits as well as its own modifications to form what it believes is the best working valvebody for the 4L60E transmission. He was adamant to point out that PerformaBuilt doesn’t block accumulators and prevent them from their intended job of eliminating shock to the transmission and drivetrain. The PerformaBuilt valvebody provides a firm and solid shift that is “linearly progressive.” That means, around town driving yields moderate bumps on shifts but once the throttle is aggressively squeezed, the shifts become more pronounced.
Anyone who has put a stock 4L60E behind a moderately modified engine can attest to the numeric trouble code of P1870. That warning code refers to converter clutch failure, which is caused by the converter shudder sensation. General Motors has a partial lock-up function on these transmissions and it never seems to work properly. Once it throws the P1870 code, the transmission will not shift into Fourth gear and the shifts become very harsh. A PerformaBuilt Level 2 Pro Race 4L60E only allows the lock-up to be either on or off.
The 4L60E can get lost in the popularity of the heavy-duty 4L80E and even some of the more popular non-OD transmissions from the General. But the fact is, not everyone needs the biggest and baddest and PerformaBuilt has several levels available to modify the 4L60E for any kind of high-performance action. The PerformaBuilt 4L60Es—of any level—are perfect for 1994-’04 Corvettes and are ideal for a swap into an earlier model Corvette for those looking to get a quality overdrive automatic transmission.
01. PerformaBuilt Transmissions mixes OEM and aftermarket parts to create its Level 2 Pro Race 4L60E, which is rated up to 700 rwhp. For those who are more daring and have a more powerful engine under their hood, the Level 3 is rated up to 850 rwhp and its milder Level 1 Pro Street is good to around 500 rwhp.
02. The cases are all OEM core units that are cleaned and then have a heat-resistant, oil-based enamel baked on. That provides a healthy look that doubles up as a protectant against corrosion.
03. A four-pinion planetary gearset is standard in both the Level 1 Pro Street and the Level 2 Pro Race (shown). PerformaBuilt also adds heavy-duty Low-Reverse clutches and [late] heavy-duty OEM low roller.
04. Here is an example of the planetary gearsets. On the right is a five-pinion planetary that is used in the Invincible line of transmissions, while the planetary on the left is the standard four-pinion. The four-pinion is plenty strong for use in both the Level 1 Pro Street and Level 2 Pro Race transmissions from PerformaBuilt.
05. The Beast sun shell replaces the flimsy factory one, and for the Invincible series, a Sonnax Smart Shell is the standard fare. The Sonnax unit is cryogenically hardened and balanced.
06. Nestled into the Beast sun shell is the late-model reaction tube and front planet ring gear, which is a factory carryover.
07. Once the ring gear is lowered into place, the PerformaBuilt technician then adds new overrun clutches.
08. If you ever watched a transmission go together, it is like a big sandwich getting assembled, with ingredients getting piled on top of the previous layer. Next on the list are the clutches—PerformaBuilt adds high-energy carbon forward clutches and BorgWarner 29-element dual cage input sprag assembly.
09-10. After the pressure plates are machined for a smoother apply surface, the attention shifts (no pun intended) to the 3-4 clutch set. PerformaBuilt uses certain steels to achieve a 0.0020-inch clearance, which enables its transmissions to have a quick and crisp shift without the bang, or “shift-shock,” as Pickering likes to call it. Harsh shifting can cause transmission damage, not to mention an uncomfortable ride.
11. This photo illustrates the complete stack of clutches and steels.
12-13. The input shaft gets brand-new Teflon seals.
14. A brand-new input drum is installed to ensure a perfectly flat and smooth surface for the high-friction band to grab onto.
15. The input shaft and drum drop into the transmission case, followed by the max-duty wide band, which is the widest red-lined band available. The band is used to engage Second and Fourth gear, so the extra width and superior friction are needed in high-performance applications.
16-17. PerformaBuilt is very selective with regard to the front pump; it will only use a 13-vane unit. All front pumps are rebuilt and modified to increase pressure and performance.
18-19. The valvebody is highly modified using several different components and techniques. Pickering was very adamant that the company doesn’t block accumulators. Its valvebodies provide firm and solid shifts with a linear curve in gear engagement. As the throttle increases, the shifts become firmer and more solid to suit the driving situation.
20. Here is a completed Level 2 Pro Race 4L60E transmission that is ready for installation. Note the red servo cover that is glaringly obvious—the billet servo is standard in the Level 2 Pro Race transmission and is a far improved upgrade from the OEM Corvette servo. This offers superior holding strength against the band in Second and Fourth gears.