Cheap(er) gasoline – yep, it is a reality and the lower cost is certainly comforting after crude oil prices sat at record highs for many years. New sources for American oil, which exploration began nearly a decade ago, have finally come online and have helped drive the price down. That has given us some relief at the gas pump and makes it easier to consume our dead dinosaur juice in plentiful helpings. We don’t want to be a Debbie-downer, but oil is a commodity and in the world of investing, commodities go up and down, which means the price-per-gallon of gasoline will eventually rise again. But alas, we have a solution to help your classic Chevy consume less gasoline but keep the fun factor at an all-time high – add an overdrive transmission to the mix.
Converting to an overdrive transmission, like the Performance Automatic 4L60E unit pictured here, will help keep the revs down on the highway but also be strong enough to handle the power under the hood. The company makes it easy with dozens of different Street Smart systems with four-, five-, and six-speed automatic overdrive transmissions designed for all types of Chevy engine packages. In fact, the company even offers specific packages to mate up with most Chevrolet Performance crate engines. The Street Smart systems include an application-matched transmission that includes a torque converter, dipstick and fill-tube, trans cooler with steel braided lines, transmission mount, and other supporting hardware if needed, such as a TV-cable, shift linkage, and vacuum lines. All electronically controlled Street Smart packages include a stand-alone transmission controller like an MSD Atomic trans controller or PCS unit.
The 4L60E is one of Chevrolet’s most popular rear-wheel drive overdrive transmissions as it enjoyed a service life that began in 1993 as the slushbox for General Motors’ truck and SUV offerings. It moved to passenger vehicles beginning with the 1994 model year. According to Performance Automatic’s Harvey Baker, 4 designates the four forward gears; L represents longitudinal, or rear-wheel drive; 60 is the torque rating (up to 360 lb-ft according to GM literature); and E indicates that it is electronically controlled. The end of the line for the 4L60E was 2002 but with millions of units in service worldwide, it has been a popular transmission in the high-performance overhaul market.
Performance Automatic offers several versions of the 4L60E transmission with horsepower capabilities ranging from 500 to 700 hp, depending on the internal upgrades and torque converter selection. Those internal modifications range from factory-fresh parts to upgraded planetary gearsets, stronger input and output shafts, hardened drum and sun shell, and, of course, Raybestos clutch packs. For applications up to 550 hp, Performance Automatic runs the standard four-pinion planetary gearset. A stronger five-pinion set is used above that threshold and both of those planetary gearsets carry the stock gear ratios of 3.06 (First), 1.63 (Second), 1.00 (Third), and 0.69 (Overdrive). An optional six-pinion planetary is available and that provides the following gear ratios: 2.84, 1.55, and 1.00, and 0.69.
There are two transmission controller choices, and the 4L60E that we followed through production was being shipped with an MSD Atomic transmission controller, which is part of the Street Smart package. The MSD controller does not need a PC for configuration as a hand-held controller allows the user to navigate the setup and control screens. Basic operations include adjusting shift points, shift firmness, torque converter controls, live monitoring, and even a dyno mode that allows consistent chassis dyno testing. The Street Smart system also includes a torque converter that Performance Automatic representatives work with each individual to match to the engine combination.
“The 4L60E electronic overdrive transmission is a great choice for any street rod, muscle car, or Pro Touring machine. This trans incorporates modern technology, is durable and reliable, can be modified to handle up to 700 horsepower, and you can put it in Overdrive and cruise anywhere,” Baker says in closing.
01. One of the common weak points of a factory 4L60E is the sun shell. Performance Automatic adds a hardened sun shell that is thicker throughout the entire piece, especially in the spline area to handle increased horsepower and torque.
02. There are three levels for the input drum. Stage 1 is a stock drum but with a reinforcement sleeve (shown) that is good up to 500 hp. Performance Automatic Stage 2 4L60E packages utilize the stock drum with reinforcement sleeve plus a hardened input shaft for applications up to 650 hp.
03. The Stage 3 drum is a hardened unit with a bolt-on pressure plate (shown) for applications above 650 hp. The billet pressure plate is resistant to flex when compared to the factory plate. Of course, the hardened input shaft is part of the Stage 3 drum package as well.
04. Four-pinion planetary gearsets (left) are used in applications up to 550 hp. A five-pinion planetary gearset (right) is added when power goes above that level. Both planetary gearsets carry the stock gearing, which is a 3.06:1 First, 1.63:1 Second, 1.00:1 Third, and 0.69:1 Overdrive.
05. Performance Automatic has an optional (and stronger) six-pinion planetary gearset that changes the gearing to 2.84:1, 1.55:1, 1.00:1, and 0.69:1.
06. Lined up are the Second gear servos, on the right is the factory unit that Performance Automatic never uses — ever. The company standard is the sturdier Corvette servo (middle) in its base 4L60E packages. On the left is the billet servo upgrade that offers a larger apply area for more holding force on the band and firmer shifts.
07. On the bottom is the Performance Automatic hardened output shaft that is rated to over 700 hp and is optional in all stages of the 4L60E. On top is the factory output shaft for comparison.
08. The four-pinion factory rear planetary gearset is always replaced with the stronger five-pinion rear planetary.
09. Performance Automatic has a custom-made gasket and seal kit that is standard in all of its 4L60E transmission packages.
10. The Low and Reverse clutches are replaced with Raybestos high-performance clutches.
11. These are the Stage 1 forward and overrun clutches; of course, they are Raybestos branded as well.
12. Here, the drum is being fitted with Raybestos 3-4 Z-Pak clutches.
13. Once the drum is filled with the appropriate Raybestos clutch packs and is assembled on the bench, it is lowered into the factory 4L60E housing.
14. On the right is the standard width Second/Fourth band, which Performance Automatic uses a Raybestos high-performance band. For higher horsepower/torque applications, it goes with the wider Raybestos band on the left.
15. The Raybestos bands feature a high-energy friction coating for superior holding strength and durability in high-performance applications.
16. Here is the Corvette servo assembly being installed in the 4L60E case.
17. The front pump is rebuilt and modified; part of the overhaul includes all-new pump vanes being installed.
18. The pump is bolted together using 18 ft-lb of torque because there are two aluminum halves. Do not over-torque the pump or you risk of distorting it.
19. The valvebody is modified in several ways to have a better lockup “feel,” upgraded Second/Third downshift springs, and pressure adjustments.
20. A new pressure manifold in the valvebody is added to all 4L60E rebuilds.
21. The 4L60E Street Smart transmission package comes with a stand-alone MSD Atomic transmission controller. It uses a hand-held controller for setup and shifting adjustments, preventing the need for a laptop/PC.
22. A new plug is installed in the 4L60E core. This is where the transmission controller plugs in.
23. All transmissions are run on a transmission dyno to ensure proper operation before being shipped. The operator shifts through all gears, including Reverse, to verify the unit is in perfect running order. Performance Automatic has a stand-alone controller wired into the dyno for electronic overdrive transmission testing.