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October 2022

6L80E Transmission Specs and Identification

6L80E Transmission Specs and Identification - Gearstar

The arrival of 6L80E transmissions – or Hydra-Matic 6L80 transmissions – on the automotive scene in 2006 showcased the considerable design change of the automatic transmissions that General Motors created. Before now, every transmission produced by General Motors was practically based on hydraulic controls. But they kept receiving new electrical elements from time to time as they modernized.

However, the 6L80E transmission was developed from scratch as an electric over-hydraulic transmission, complete with microprocessor control, and used extensively in trucks. Now, being more than 25 years since the last non-electronic transmission produced by General Motors, the 6L80E is recognized – otherwise referred to as the 6L80.

General Motors created this transmission to make the organization meet the demands of CAFÉ regulations on their automobiles. This 6-speed automatic, longitudinal transmission utilizes more gearing that keeps your vehicle running longer within its power band, significantly boosting the miles per gallon (MPG) of the car between 4 to 7 percent over the previous generation’s 4-speed transmissions.

But, of course, this depends considerably on the configuration of the vehicle the transmission is in. The 6L80E replaced the 4L60E in several vehicles, especially from the 2006 model year. It was primarily found in large cars powered by V8 motors. The 8L90E transmission may have phased out this automatic transmission, but it is still in production. Some of these vehicles in which you will find the 6L80E automatic transmission include:

6L80E Transmission Specs

The 6L80E automatic transmission is robust and capable of handling lots of power. It is known to handle a total gross vehicle weight of up to 8,600lbs, making it one of the greatest transmissions for LS swaps with zero modification required. The input torque rating of this transmission is 440lbs. As you may have already guessed, this transmission is primarily designed for rear-wheel drive vehicles only. It comes with a line pressure tap integrated only for diagnostic purposes.

6L80E Transmission Gear Ratios

The 6L80E automatic transmission makes use of 4 underdrive gears as well as two overdrive gears. As a result, it doesn’t have the usual direct 1:1 ratio like the 4L60E and 4L80E transmissions. Here is the gear ratio of the 6L80E automatic transmission:

  • First gear — 4.027
  • Second gear — 2.364
  • Third gear — 1.532
  • Fourth gear — 1.152
  • Fifth gear — 0.852
  • Sixth gear — 0.0667
  • Reverse — 3.064

The 6L80E transmission’s RPO code is ‘MYC’ and is manufactured domestically in GM’s Michigan plant. It employs a direct clutch-to-clutch shifting with zero bands.

6L80E Transmission Identification

You can identify the 6L80E in two unique ways. However, your identification method depends primarily on whether the transmission is still mounted in the vehicle or has been dismounted. If the 6L80E transmission is still mounted in the vehicle, you can only identify it using its RPO tag in the vehicle’s glove compartment. This is why knowing the RPO code for the transmission you want to identify is nothing short of golden. For instance, here’s a list of GM transmission RPO codes you should know, arranged in no particular order:

  • 6L80E — MYC
  • 6L90 — MYD
  • 4L65E — M32
  • 4L60E — M30
  • 4L80E — MTI

You will always find one of these sheets in the glove compartment of modern GM vehicles. Get hold of one and use it to confirm the identity of the transmission in that particular vehicle. But suppose the transmission has been dismounted from the vehicle. In that case, you will quickly recognize the 6L80E automatic transmission since it has an 18-bolt case, which is considerably more than any other automatic transmission from General Motors.

6L80E and 6L90 transmissions are almost identical and interchangeable for all practical purposes. However, the 6L90 transmission has several internal upgrades and a beefier set of gears. This is why using the pan gasket is considered the easiest way to identify or tell most General Motors transmissions apart. The major automatic transmission that the 6L80E will be confused for all come with different numbers of pan gasket bolts.

Therefore, ensure to count the pan gasket bolts carefully. The torque converter with the 6L80E transmission is a fluid turbine drive. In addition, it features a lock-up pressure plate for direct mechanically-coupled driving from the engine crank, just like those found in the 6L80E’s predecessor transmissions, such as the 4L80E, TH350C, 4L60, and 700R4 transmissions.

Differences Between 6L80E and 6L90E Transmissions

The 6L90E succeeded the popular 6L80E. The former is primarily designed to transform the extra torque efficiently. The 6L90E transmission was essential as new automobiles with more significant performance were required to hit the market. The most significant difference between the 6L80E automatic transmission and its successor, the 6L90E transmission, can easily be traced to its internal components.

Starting with their case: the case of the 6L90E transmission is shorter than its predecessor. The primary reason for this unique design was to enable this transmission to accommodate additional physical gear assemblies adequately. Owing to this, this automatic transmission permits two extra pinion gears, which equates everything to six. This essential modification is vital for high RPM and high torque figures.

However, this also resulted in a biggish shaft to ensure 100 percent reliability, which is more noticeable during loaded 3-4 upshifts where the shaft experiences enormous stress. More than a few applications came with several clutches peppered across multiple clutch packs in the automatic transmission. This significantly boosts the load capabilities of the clutch packs within the gears to which they are applied readily.


So, there you have it: the glorious specs of the high-performance 6L80E automatic transmission and its identification characteristics. The 6-speed, longitudinal automatic transmission powers several GM trucks and a wide range of vehicles alongside its successor, the 6L90E model. You should have no trouble recognizing the robust 6L80E in a lineup of identical transmissions.

Rebuilding a Faster, Better TH400 in Almost Every Way

Rebuilding a Faster, Better TH400 in Almost Every Way - Gearstar

Rebuilding a transmission, such as the TH400, is not relatively as easy as changing your car filter or making an oil change. It is a challenge that will take a good mechanic almost all weekend. But if you don’t possess the skills of a mechanic, you shouldn’t attempt rebuilding your transmission. It is highly recommended that you leave this project in the hands of professionals. Here’s what you need to know about TH400 transmissions and how to rebuild them for faster and better performance.

Overview of TH400 Transmission

The TH400 transmission – or Turbo 400 transmission – was General Motors vehicles’ brainchild in 1964. This transmission was designed to substitute the ST300 2-speed automatic transmission. The TH400 transmission was used in Pontiacs and Cadillacs in the first year but somehow found its way to Chevrolets, Oldsmobiles, and other models by 1965.

The TH400 transmissions from 1965 to 1967 featured a mechanical device known as a variable pitch stator. This feature helped the torque converters characters in the transmissions and can easily be identified by the 2-prong plug on the case. By the time the ’70s arrived, the TH400 transmission was already used in heavy-duty GM trucks in 2WD and 4WD versions. 

In 1990, this transmission changed from TH400 to 3L80, resulting in longitudinally positioned 3-speeds and 8,000lbs. GVW or Gross Vehicle Weight. This name change was necessary as it made readily identifying the transmissions easier. This was also the year an early introduction of the 4L80-E transmission, the successor of the Turbo 400 Transmission that has overdrive, was made.

The TH400 transmission is an electronically-controlled, heavy-duty version of a TH350. The Turbo 400 Transmission required a kick-down switch by the gas pedal to inform the transmission when to kick down a gear. Military and heavy-duty GM vehicles still use this transmission as it is still produced today.

Features of the TH400 Transmission

The Turbo 400 transmission is a highly durable gear mechanism that offers improved performance over its predecessors. One common feature of the TH4oo transmission is its iron and aluminum construction. In addition, it has three tail shaft lengths and bell housing integrated into the transmission.

  • First gear – 2.48:1
  • Third gear – 1:1
  • Reverse gear – 2.08:1

The TH400 transmission weighs 135 pounds minus the fluid.

Identifying the TH400 Transmission

The Turbo 400 transmission has a main cast aluminum case measuring 24-3/8 inches long. This aluminum case is smooth. The rear mounting face of this transmission showcases a bold hex pattern with several ribs that run forward longitudinally. The shape of the fluid pan is somewhat irregular, likened to a distorted Texas pattern. The TH400 transmission is admittedly the largest of the regular General Motors transmissions.

Nevertheless, it is surprisingly compact, considering the immense power it can handle. General Motors created two significant variants of the Turbo 400 transmission. The first variant, i.e., the TH375 transmission, was made public from 1972 to 1976 in smaller displacement vehicles. It was used extensively in several small vehicles and easily identified by the ‘375-THM’ lettering carefully etched on the bottom or underside of the tail housing.

The other variant of the Turbo 400 transmission was the TH475; a heavy-duty transmission used extensively in large trucks from 1975 onwards. You can quickly identify the Turbo 400 transmission by checking out its kick-down assembly. This transmission uses an electric slide switch that controls the throttle linkage mechanism. On the other hand, the TH350 transmission uses a mechanical relay or cable kick-down mechanism attached to the throttle linkage.

Rebuilding the TH400 Transmission to Your Engine

The TH400 transmission is respected and loved due to its versatility and durability. However, there will come a time when the old transmission shows signs of wear and tear. Even the best transmissions are rebuilt at one point or the other. Wholly and correctly rebuilding an automatic transmission like the TH400 is ordinarily not beyond the capabilities of the average DIY automotive enthusiast. But there is always something that keeps away even pro automotive mechanics or technicians when rebuilding an automatic transmission.

Some claim not to have the necessary tools, while others say they don’t have enough time to carry out the task, so they whisk off the tranny to a specialty shop. As mentioned earlier, rebuilding a transmission is not an easy task. But the truth is that most of the tools required are standard hand tools. If you are not 101 percent sure of what you’re doing, best leave this task to professional mechanics. In this light, here are some of the tools required for rebuilding your TH400 transmission:

  • Safety equipment (eye protection, nitrile gloves, heavy-duty gloves, hearing protection, etc.)
  • Wrenches and sockets
  • Screwdrivers
  • Spring compressors
  • Snap ring pliers
  • Measuring devices
  • Pans for small components
  • Case holding features
  • Work surface
  • Busing removers and installers
  • Cleaning cases, etc.

When racing a Turbo 400 transmission, it is crucial to upgrade the direct and forward drums. The key revolves around more durable and stronger components and boosting efficiency for better performance, safety, and consistency. You can get a radical edge over other users by upgrading your TH400 to maximize drum function with unique configurations of more robust and lighter components. This development significantly boosts the efficiency and performance of your TH400 transmission for more power to the ground and stability/traction on the shifts.


The Turbo 400 – or TH400 – transmission is one of the automotive industry’s most widely used and versatile performance transmissions. This remarkable transmission has proven to be capable of handling massive power and is incredibly adaptable. This is not evident only in General Motor applications but also adapted behind Chrysler, Ford, and other engines.

You can maximize the reliability and performance of the TH400 transmission to make it deliver that exceptional result you trust at any power level. However, unless you are a certified mechanic or technician, it is highly recommended that you allow pros to handle the rebuilding of the TH400 transmission on your behalf.

A Detailed Look at Today’s High-Performance Automatic Transmission

A Detailed Look at Today's High-Performance Automatic Transmission - Gearstar

If your AT experience in sports and muscle cars is limited to the three- and four-speed slushboxes of yore, let us say this: today’s high-performance automatic transmission is nothing at all like them.

The early dislike for automatic transmissions seems to have melted away. These transmissions were once inefficient, clunky, and slow as they often provided one less ratio than a manual transmission, even in the exact vehicle. However, cars with automatic transmissions became point-and-go machines since shifting their gears required zero human intervention. As a result, these automatic transmissions have made driving more manageable and have become widely available.

Transmissions are primarily designed to assist in moving a vehicle with minimal effort from its engine. As a result, automatic transmissions are very convenient, mainly when you are trapped in busy traffic situations where you must stop, start, and shift gears frequently. They are also excellent options for beginners, particularly when on an upgrade. Automatic transmissions also make a hill start incredibly easy while giving you all the freedom you desire from the clutch. The computer system in a vehicle is the only entity whose complexity surpasses that of transmissions.

Why a High-Performance Automatic Transmission?

Have you ever wondered why some transmissions are referred to as ‘high-performance’ transmissions? It is because high-performance automatic transmissions are much more carefully engineered and built for engines capable of speed and exceptional performance. There was a time when this gear mechanism was limited to only a few vehicles. These vehicles were typically used only for street racing or racing on the drag strip. But this line has been blurred over the years, and many cars now have high-performance automatic transmissions.

Gone are the days when numerous car enthusiasts reserved specific vehicles for drag or street racing. Instead, they have gone out of their way to outfit their unique daily drivers to make them adaptable enough to conform to numerous everyday roles. In other words, it implies modifying their existing muscle vehicles to meet their objectives: a dependable daily driver and a reliable tear-up-track or tear-up-the-street vehicle by night or on weekends.

Types of Vehicle Transmissions

Three primary transmissions exist automatic, manual, and electric. Both automatic and manual transmissions have service intervals. However, since they are sealed units, electric transmissions don’t have service intervals. Modern paddle-shifted automatics, especially those with up to 10 gears, usually post better acceleration numbers than manuals. 

Understanding Automatic Transmissions

The automatic transmission delivers torque from the car engine to the wheels, providing optimal power for negotiating numerous driving conditions. Both automatic and manual transmissions offer a fixed number of gear ratios. In contrast, a CVT (continuously variable transmission) theoretically gives an infinite number of gear ratios within a specific fixed range. You can achieve this in vehicles with manual transmissions by selecting the right gear, though this depends significantly on the prevailing driving conditions.

But on the other hand, automatic transmissions select the ideal gear ratio without human intervention. Manual transmissions require maintenance from time to time and must be checked during periodic service. However, manual transmission issues can usually be fixed or repaired without fuss. But continuously variable transmissions and automatic transmissions are comparatively maintenance-free, according to most vehicle manufacturers. 

Improving the Reliability of Your High-Performance Automatic Transmission

There are six ways you should consider if you want to improve the reliability and performance of your automatic transmission. They are as follows:

1. Service Your Automatic Transmission

In an ideal case, automatic transmissions last between 300,000 km to 400,000 km. As a result, most vehicle manufacturers claim that their automatic vehicles do not need transmission fluids. Therefore, you don’t need to change your vehicle’s transmission fluid unless you have a leak. But practically, as with most things in life, things are not all that smooth with the majority of automatic transmissions.

Most automatic vehicles will notice strange transmission-linked symptoms, especially after approximately 150,000 km. Servicing usually helps fix or prevent these issues. However, according to most vehicle manufacturers, there is no need for transmission fluid changes. But in reality, the essential properties of transmission fluid usually start deteriorating with time or age. This means changing your automatic transmission’s fluid would be necessary.

Saving the automatic transmission is always easier during the early stages. But there’s no harm in undertaking a transmission fluid flush later. In most cases, changing the transmission fluid restores its performance to a greater extent, whether or not the symptoms are acute. However, there is no 100 percent guarantee, but the transmission fluid change often works. This is an excellent and inexpensive way of fixing automatic transmission issues.

This is because a brand-new transmission costs nearly ten times the amount it would take to flush your transmission fluid. Therefore, attempting the repair makes sense. Although it won’t restore the automatic transmission to its full initial performance, some symptoms may suddenly disappear while others get less dramatic. However, it is highly recommended to maintain automatic transmissions during the early stages than to risk this occurrence.

2. Change Your Driving Habits

Always allow your vehicle’s engine to warm up for several minutes before you shift into drive. This is crucial, especially during the winter months.

3. Change Your Transmission Filter

This depends on the model and makes of your car. Your vehicle’s automatic transmission may come with a filter that needs to be changed regularly. However, newer model vehicles don’t have transmission filters.

4. Never Change Gears While Your Vehicle Is in Motion

Ensure your vehicle stops completely before changing gears to ‘reverse’ or ‘drive,’ or vice versa. If you don’t, you unnecessarily put a strain on your automatic transmission. This could result in severe issues down the road if you keep this up for an extended period.

5. Always Use the Recommended Type of Transmission Fluid

Consult your car’s owner’s manual to determine your vehicle’s ideal type of transmission fluid.

6. Service Your Engine’s Cooling System

The job of your vehicle’s cooling system is to prevent the engine from overheating. But only a few car owners know that the cooling system also cools the transmission fluid pumping through the gearbox. It is far more likely to require a transmission repair before your car engine overheats. Therefore, ensure your cooling system is in ideal condition.

Final Takeaway

Automatic transmissions are taking over the day as manual transmission dies out slowly. These transmissions were once inefficient, clunky, and slow but have become the point-and-go machines we know today. In addition, these automatic transmissions have made driving easier and have become widely available. You can improve the reliability and performance of your automatic transmission by following the tips highlighted above.

C6 Transmission Upgrade Tips, Tricks, and Tech

C6 Transmission Upgrade Tips, Tricks, and Tech - Gearstar

Have you ever wondered if it’s possible to upgrade your C6 transmission to meet modern-day expectations in terms of toughness and performance? Yes, it is likely because experts have done it. You can revamp – or purchase a C6 performance transmission – rebuilt to handle anything you throw at it. Bear in mind that the C6 was built to provide long-term durability. As a result, it came to the fore in the powerful Ford trucks of the ’70s and high-performance Mustangs and sedans. This means you will get more than decent results if you upgrade your C6 transmission to meet modern-day standards. However, you may need to fish out some powerful components that will help take your C6 a little further to ensure you enjoy the best horsepower. Here’s what you need to know about the C6 transmission and a few upgrade tips you should consider.

Overview of the C6 Transmission

The Ford C6 transmission is the Ford Motor Company’s brainchild and prevailed from 1966 to 1996. It is a beefy 3-speed, heavy-duty automatic transmission heavily marketed as the SelectShift Cruise-O-Matic by Ford. This automatic transmission had a 30-year service life, after which Ford released it to give room for the modern overdrive versions of the company’s extensive transmission line-up. The C6 automatic transmission is somewhat lighter and has a less complex build than its predecessors. As a result, it offers less power loss and greater torque capacity, especially compared to its immediate predecessor’s MX transmission. The design of the MX transmission fooled many users, but the C6 achieved enormous capabilities with its more petite build.

Moreover, the C6 automatic transmission is simpatico to the Borg-Warner flexible shift band. The primary goal of making the C6 compatible with the adjustable shift band was to boost its durability and service life significantly. Despite the delivery of this purely mechanical – i.e., zero electronic controls –automatic transmission, it has a downside worth noting. First, it is beefy, meaning it weighs quite a lot. This causes valuable horsepower to be lost to turn the pieces and parts. However, this is gradually changing due to the possibility of merging customized components with specified C6 parts and particular pieces of the modern-day 4R100 electronic-overdrive sibling. The outcome is a powerful transmission unit capable of withstanding any abuse while negating the power-robbing pickles of the original C6 automatic transmission design.

C6 Transmission Gear Ratios and Vehicle Compatability

The stock C6 transmission from the factory features the following gear ratio:

  • First gear = 2.40:1
  • Second gear = 1.40:1
  • Third gear = 1:1

A brand-new wide-ratio gearset is installed, which offers a numerically more excellent gear ratio viz:

  • First gear = 2.72:1
  • Second gear = 1.54:1
  • Third gear = 1:1

This higher first gear is of much assistance with heavier vehicles since it makes the rear gear behave larger without unnecessarily boosting the highway cruising rpm. Some of the vehicles with the C6 automatic transmission include:

  • 1964 — 1970 Ford Fairlane
  • 1966 — 1974 Ford Galaxie
  • 1966 — 1980 Ford LTD
  • 1966 — 1979 Ford Thunderbird
  • 1966 — 1979 Ford Ranchero
  • 1966 — 1969 Ford Mercury Comet
  • 1966 — 1979 Ford Lincoln
  • 1966 — 1972 Ford Mercury Meteor
  • 1967 — 1996 Ford F-Series
  • 1967 — 1973 Ford Mustang
  • 1967 — 1978 Ford Mercury Cougar
  • 1968 — 1976 Ford Torino
  • 1977 Ford Mustang Cobra II

Therefore, upgrading your C6 automatic transmission should be part of your plans if you own any of these classic vehicles. Thus, it is essential to equip your C6 to combat common transmission problems.

C6 Transmission Upgrade Tips and Tech

Nothing should dampen the joy of driving a classic car on modern roads or cruising around town. But you can only guarantee this when you upgrade your C6. Therefore, here are a few tips that will come in handy when upgrading your C6 automatic transmission:

Modify the Parking Pawl Gear

Several small details of the C6 automatic transmission can be upgraded. This includes the modified parking pawl gear. In addition, it can be machined down such that it fits a needle-bearing assembly rather than a thrust washer. When the parking pawl gear accelerates, it pushes outward. This is entirely satisfactory until you ease off the gas pedal and go to deceleration. Switching to a needle bearing keeps the case from getting worked over on deceleration. At this point, the input shaft exerts lots of pressure on the housing. Modified parking pawls prevent severe damage from the strains that deceleration causes.

Replace the Planetary Gearset With a Stronger Counterpart

The First and Reverse planetary gearset in a C6 automatic transmission feature a 3- or 4-pinion unit. Each of these is constructed with aluminum. This is replaced with a 6-pinion, super heavy-duty steel planetary gear set. The extra pinions help to efficiently disperse the load since the steel material is more robust than its aluminum counterpart.

Work on the Lincoln Drum

The Lincoln drum refers to the Third-gear/direct drum featuring a higher snap-ring groove. This groove gives room for the installation of more clutches. A factory-fitted Lincoln drum uses four clutches, while the other third-gear drums only have three clutches. However, you can fit up to 6 brand-new high-performance clutches within the Lincoln drum for an enhanced grip.

Upgrade the Valve Body

You can get experts to upgrade the valve body, which allows for manual action (reverse and forward) or automatic shifting. In addition, you may require a valve body shift kit that promises to give firmer shifts to do away with annoying issues like clutch chatter, band failure, and a premature clutch. Drag racers can also install a trans-brake while settling for a deeper oil pan (optional) or using thicker high-performance bands.

Work on the Aftermarket Clutches

You can do away with stock clutches and go for less thick but highly durable aftermarket options. For example, stock clutches are usually 0.0080 inches wide. But you can find aftermarket options that are not thicker than 0.0065 inches.

Shifting Into High Gear

These are just a few tips you should consider and follow for upgrading your beloved C6 automatic transmission. This exercise ensures your transmission attains the level of performance its modern-day counterparts are accomplishing. The C6 automatic transmission already has a pretty solid foundation; all you need to do is to work on the suggested areas, and you’ll be good to go!