The final two numbers relate to torque capacity with 80 and 90 offering much more load capability than a 30 or 40-rated transmission.Before you fire up the email attacks, this story is intentionally ignoring a whole slew of GM automatics that are best described as obscure like the TH350C lockup, the TH475, the ill-fated TH-200, and several others. So let’s get started by first breaking down the alpha-numeric transmission identity puzzle.The first number that appears is the number of forward gears followed by a letter that is only going to be either a T for transverse (front-wheel-drive or FWD) applications or L for longitudinal or rear wheel drive (RWD). We’ll also clue you in on what those numbers and letters mean, although it’s far less complicated than trying to decipher Ford and Chrysler’s gearbox hieroglyphics. We will briefly touch on the older transmissions like the TH350 and TH400 and the 700-R4 / 200-4R but since all of these gearboxes have earned a wealth of individual attention there’s little need to recap them here.The focus of this story will be on the electronically controlled transmissions like the 4L60E, 4L80E,6L90E, 8L80E and the most current in the 10L90E. Drain/Fill or Flush What type of oil - I have heard so many bad things about flushing.This story will outline the transformation, if you will, from the Powerglide all the way to the new 10L90E transmission that sits behind the 650 horsepower ZL1 supercharged Camaro with a dizzying collection of automatic gearboxes in between.
More than 50 years later, it retains much of its popularity and was the engineering basis for the four-speed overdrive 4L80E that appeared in the early 1990’s.If the TH400 has a limitation, it is in its heavy rotating mass. The Turbo 400’s First gear ratio of 2.48:1 offered excellent gear multiplication and it soon became the first choice for street and drag racing applications based on its strength and durability. The oil pan is also "Texas" shaped, though that might take a bit of imagination.The top dog among the GM three-speed automatics appeared in 1965 in the passenger car lineup behind the 396 big-block, multiple truck applications, and later in the Camaro, Chevelle, and Corvette. So let’s start with the simplest and oldest of the GM automatics.Conversely, on a TH400, a quick identification is that the vacuum modulator valve is positioned on the passenger side of the case nearer the front of the main case.
This transmission is often mistakenly lumped in with the TH-200 three-speed automatic that GM attempted to make work in the early ‘80s. The TH400 is also significantly larger and heavier and uses a larger, 32-spline output shaft compared to the TH350’s 26-spline output that it shared with the Powerglide and Muncie four-speed manual gearboxes.The first overdrive automatic to transfer power in the GM lineup was the 200-4R that arrived in 1981 behind A- and G-body cars as well as full-size sedans. The TH400 places the vacuum modulator valve closer to the front of the case on the passenger side while the TH350 positions the valve at the very end of the main case on the passenger side. The aftermarket has addressed this issue with a tremendous number of performance upgrades to the extent that a complete TH400 transmission can now be built with aftermarket parts – offering a tremendous number of different opportunities for street and race applications.There are a couple of quick and easy ways to identify a TH400 compared to its smaller TH350 cousin.
As the cable moves, this increases line pressure in the transmission to properly apply and load the clutches and bands. This system used a cable assembly tied to the throttle linkage as the load indicator to the transmission. This transmission eventually found favor when employed behind turbocharged Buick V6 cars like the Buick Grand National and GNX but could also be found in other applications like the G-body Monte Carlos SS and Oldsmobile 442.The 200-4R was the first to replace the vacuum modulator valve with the throttle valve (TV) cable system.
Holley offers an excellent conversion bracket for the 4150/4160 style carburetors (PN 20-121) along with a cable mounting bracket at the rear of the carburetor (PN 20-95).There are actually two versions of the 700-R4, with the early ones employing a 27-spline input shaft that was upgraded around 1987 to a larger, more robust 30-spline input shaft that logically also requires a different torque converter. The 700-R4 also employs the TV cable arrangement to signal load to the transmission in exactly the same manner as the 200-4R.A problem area for the 700-R4 in aftermarket applications is the throttle valve (TV) cable adjustment. While similar to the 200-4R, it operates somewhat differently, with a deeper First gear ratio of 3.06 vs the 200-4R’s 2.74:1 with a nearly similar 0.70:1 overdrive ratio. Transmission builders such as Art Carr’s California Performance Transmissions and several others can assemble one of these transmissions into an excellent street trans.Following the 200-4R one year later in 1982 was the 700-R4. But when properly built and modified, the 200-4R has outstanding potential as an overdrive automatic in a street performance application.
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There are multiple companies now that offer a stand-alone controller for the 4L60E family of transmissions, including the MSD Atomic Transmission Control Module, and both Holley’s Dominator and Terminator X ECU versions also offer transmission control over the 4L60E/4L80E family of four-speed automatics.The 4L60E went through some case changes during its tenure. Plus, the torque converter lockup could also now be controlled with the same ECU. The big improvement was total electronic control which eliminates the need for the troublesome TV cable and also did away with the spinning weights and springs used in the governor, since input and output speeds are now measured by sensors and the up and down-shifts are controlled by an electronic transmission controller.The advantage for the performance enthusiast is that this transmission can now be controlled electronically to up-shift at wide-open-throttle at very specific engine speeds which was difficult to achieve with the 700-R4’s mechanical/hydraulic control. Despite the 700-R4 / 4L60’s somewhat undeserved reputation for problems, there is a wealth of aftermarket upgrade parts that make it capable of handling power well in excess of 500 to 600 hp.To accommodate a larger input shaft and torque converter, the 4L60E evolved with a larger bellhousing area that can be easily spotted since it employs the LS style bolt pattern using the top middle bellhousing bolt.GM upgraded the 4L60 to electronic control with the 1993 model year and these transmissions were used in a wide variety of applications from the Camaro and Corvette to full size cars and light and medium duty trucks. Despite the name change, operation of the transmission remained exactly the same. The 700-R4 has suffered from a somewhat checkered reputation as a performance transmission in the aftermarket unfortunately due in large part to improper TV cable adjustment.In 1990, GM changed its automatic transmission nomenclature and the 700-R4 became the 4L60.
This trans is significantly larger and heavier than its three-speed predecessor, but like the 4L60E it is easily employed for performance use in earlier vehicles by using the same aftermarket controller that manages the 4L60E.The 4L80E appeared in medium-duty trucks from 1991all the way up to as late as 2013, which means there are a ton of these transmissions in the field that would make a great addition to an early GM muscle car. The TH350 / 200-4R / 4L60E’s slip yoke (left) is somewhat smaller in diameter and spline count (27) than the TH400 / 4L80-E’s 32 spline output shaft.Looking to improve highway mileage on late model trucks, beginning in 1991 GM upgraded the original TH400 by adding a 0.70:1 overdrive along with complete electronic control to create the 4L80E. The big durability factor is aftermarket and heavy-duty factory pieces that push the original 4L60 trans well into 4L80E torque territory.One way to judge torque capacity is to look at the output shaft diameter / spline count. This last one can be identified by its bellhousing bolt hole located at the 12 o’clock position.There are also several performance variants to the original 4L60E including those from, B&M. One year later, in 2000 it changed again with a deeper bellhousing to accommodate a 300mm input shaft and larger torque converter. In 1999, the 4L60E converted to a bolt-on bellhousing.
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