Electric solenoids and advanced...
Electric solenoids and advanced engine management actually made the internal workings of the 4L80-E, 4L85-E, and the 4L85-E SuperMatic simpler than their predecessors. Automatic shifting of the transmission is accomplished via the apply and release of the clutch packs and bands, which are directed by the hydraulic-control components shown here.
To further the durability, the output and reaction gear sets were fitted with five pinions, instead of the four found in the 4L80-E. "Within the output and reaction gear-set carrier assemblies, the smallest gears are the pinions that revolve around the sun gears. Increasing the number of pinion gears from four to five allows the gear set to handle higher loads," according to GM. There's also a 34-element intermediate sprag, induction-hardened input shaft, and hardened forward hub. The torque rating for the 4L85-E is 460 lb-ft.
Now we have the 4L85-E SuperMatic (GMPP PN 19154550), introduced in 2009. It was designed to work behind high-torque engines like the Chevy ZZ572/720 crate package, and is advertised as a direct bolt-in for the Chevy Gen 1 small-block and all big-blocks. To bolt one into a Pontiac, we employ a bellhousing adapter.
GM Performance Parts tested the torque capacity of the 4L85-E using a 572/720R big-block Chevy crate engine. Afterward, the trans was torn down and examined for wear. Rusty Sampsel, GM Performance Parts Continuous Improvement Technical Liaison, tells HPP, "We took it apart and looked for areas that could be improved, and made those improvements. More clutch plates with upgraded materials were added in the intermediate, direct, and forward clutches, as was an improved overrun roller and selective-fit intermediate sprag outer race. Other modifications were made to the direct-clutch housing to improve longevity by preventing centrifugal apply at high rpm." An increase in fluid pressure and a revised firm-shift valvebody round out the upgrades.
Following the improvements, the transmission was back on the dyno (with the big-block ahead of it) for durability testing. Subsequent teardown verified that the new design was able to handle to at least 720 hp and 685 lb-ft of torque reliably.
The PCM monitors both engine...
The PCM monitors both engine and transmission signals through sensors to determine the shift points and line pressure required.
The gear ratios are the same as the 4L80-E and 4L85-E: 2.48 First, 1.48 Second, 1.00 Third, and 0.75 Fourth. Most Pontiac hobbyists who are into vintage models will quickly note that the first three forward gears are the same as the famed Turbo 400, from which these transmissions were originally derived. To use this electronically-controlled transmissions in a vintage Pontiac, electronic controller GMPP P/N 12497316 is required.
The 4L85-E SuperMatic is a fully automatic four-forward-speed transmission with electronic controls. It is designed with a four-element torque converter, three planetary gear sets, a hydraulic pressurization and control system, along with both friction and mechanical clutches. Its four-element torque converter contains a pump, a turbine, a pressure-plate splined to the turbine, and a stator assembly. The torque converter acts as a fluid coupling and is able to multiply engine output when required. The pressure plate, when applied, provides a mechanical direct-drive coupling of the engine to the transmission (lock-up), which eliminates any inherent slipping.
Three planetary gear sets provide the four forward speeds and reverse. Changing gear ratios is fully automatic and is accomplished through the use of a powertrain-control module (PCM). The PCM receives and monitors various electronic-sensor inputs and uses this information to shift the transmission at the optimum time with the required line pressure. It commands shift-solenoid valves within the transmission on and off to control shift timing, and it also controls the apply and release of the torque-converter clutch, which allows the engine to deliver maximum fuel efficiency without sacrificing vehicle performance.
With the engine running, the...
With the engine running, the fluid flow begins at the torque converter.
Its hydraulic system primarily consists of a gear-type pump and control valvebody. The pump maintains the working pressures needed to stroke the servos and clutch pistons that apply or release the friction components. These friction components (when applied or released) support the automatic shifting qualities of the transmission. Friction components in the 4L85-E Supermatic consist of five multiple-disc clutches and two bands. These combine with three mechanical components, two roller clutches, and a sprag clutch to deliver four different gear ratios through gear sets, which then transfer torque through the output shaft and out to the drive axles.
Look for a complete install of a 4L85-E SuperMatic in an upcoming issue.
HPP would like to thank Tom Read, GM Advanced Technology Communications, Powertrain; and Patrick "Zak" Walczak of GearStar Performance Transmissions in Akron, Ohio, [(800) 633-2353] for their technical assistance.