was successfully added to your cart.




The Ultimate Guide to the 4L80E Transmission

Overview of the 4L80E Transmission - Gearstar Performance

The 4L80E transmission is an automatic transmission designed by General Motors. Learn more about this legendary transmission.

The 4L80E transmission was introduced in the GM C/K Trucks line-up – to the delight of motorists – in 1991. The legendary TurboHydramatic TH400 automatic transmission was the 4L80E transmission’s immediate predecessor. It is constructed to a great extent on the 400 in strength and parts. The 4L80E also features a lock-up torque converter, an added overdrive gear, as well as state-of-the-art electronic controls. This automatic transmission has remained in production through the 2009+ model year.

In this post, you will learn more about the 4L80E transmission and its variant, i.e., the 4L85E. The latter is constructed such that it can efficiently handle heavy-duty use. Every reference to the 4L80E also applies to this variant, except where stated otherwise. 

Note that the terms’ 4L80′ and ‘4L85’ may be used without adding the suffix, ‘É.’ This is because every GM automatic is electronically controlled now and, therefore, doesn’t need differentiation. 

Let’s get to the meat of the matter.

The Development of the 4L80E Transmission

As mentioned briefly earlier, the 4L80E automatic transmission was directly developed from the TH400 transmission. The latter is a challenging and enduring transmission at GM – as well as other marques. It was practically the last hold-out of the entire old-school automatics with no overdrive or lock-up converter.

GM quickly recognized a gap revealed by the rapidly expanding success of the 4L80E/700R4 automatic transmission. Although the 700R4 was a tough transmission, it could not hold a candle to the TH400 transmission. 

And for this particular reason, GM had no choice but to start developing a pretty heavy-duty automatic overdrive.

GM relied heavily on – and used – several parts or components and designs derived from the TH400 transmission when developing the 4L80E. But the added overdrive gear gave the 4L80E an edge over its predecessor, even though it required a somewhat longer case and an extra gear set.

The rear tail housing bolt pattern was not tampered with in any way. However, its indexing bore diameter was efficiently changed. The 4L80E transmission features a large 32 spline output shaft – much like the TH400 transmission – in the numerous 2WD and 4WD applications.

The 4L80E features a die-cast aluminum case, just like most other GM automatics. However, the 4L80E never featured a removable bell housing, unlike the 4L60E automatic transmission. Instead, the 4L80E transmission showcases an integrated bellhousing with the Chevrolet 90-degree engine bolt pattern only.

In 1991, GM trucks rolled out into the market, bearing the 4L80E automatic transmission. This included the Silverado, Sierra, Suburban, Hummer H1, etc.

The 4L80E automatic transmission is by no means perfect and has its share of glitches. However, it became a huge success and continued to be enhanced throughout its production span, even with extra changes entering when required.

In 2002, the 4L85 automatic transmission entered the market. A few differences between this transmission and the 4L80E include a 5-pinion reaction gearset, a 5-pinion output gearset, etc.

GM specified a brand-new automatic transmission fluid formulation in 2006, though this development was not regarded as a transmission change. The company required this fluid formulation’s warranty in the 4L80E series. Dexron VI, another brand, highly superseded its previous transmission fluids, claiming that it has significantly improved the transmission performance as well as a more extraordinary fluid life and transmission.

The 4L80E Automatic Transmission Technology

Every 4L80E automatic transmission makes use of electronic controls, which are generally from the Powertrain Control Module. Some vehicles using this automatic transmission come with shift maps that the driver can select, based on usage, including towing, etc. 

Part of the Powertrain Control Module’s strategy includes shift stabilization, which contributes significantly to reducing hunting.

The torque converter – when applied in factories – is heavily controlled via a PWM lock-up solenoid for seamless lock-up action. Despite this, several performance aficionados always prefer to efficiently reprogram the 4L80E automatic transmission in order to run as a very simple, ON-OFF solenoid.

The H1 received a 4L80 along with its dedicated T42 transmission computer in 2004. This automatic transmission also arrived with a considerably enhanced Park/Neutral safety switch and modified transmission line pressure solenoid. Other General Motors applications are still going to follow soon.

The TCM (Transmission Control Module) refers to the highly adaptive learning computer smartly integrated within the transmission valve body. It communicates efficiently with the Engine Control Module through the onboard vehicle CAN bus network. 

This is a departure from – and a return to – preceding automotive control systems within the industry. This is because the earlier versions of electronic transmissions made use of a separate control module. This module was later integrated right into the Engine Control Module and is now known as the ‘Power Control Modules.’

But now, this high-speed CAN network permits an incredibly high rate of data sharing between these units. This occurs in order to reach a collaboration between transmission and engine functions.

Since the 4L80E automatic transmissions are – on certain occasions – used in conversion applications with the earlier non-PCM-controlled engines, GM as well as aftermarket control modules are necessary. And they are now used to control the operation or function of the transmission in these specific scenarios.

The Specifications

When you see the nomenclature of the 4L80E, it readily informs users that this is a longitudinally-mounted, 4-speed transmission designed for vehicles that weigh nothing less than 8000 lbs. The 4L80E has an RPO code – i.e. ‘MT1’ – manufactured domestically in GM’s Willow Run and Ypsilanti plants.

Here are the 4L80E ratios it features in each gear:

  • First: 2.48
  • Second: 1.48
  • Third: 1.00
  • Fourth: 075
  • Reverse 2.07

The maximum output torque of the 4L80E transmission is 885 ft. lbs. 

While the top engine input torque is 440 ft. lbs. Die-cast aluminum is the transmission’s case. And it was designed for vehicles that weigh up to 8,000 lbs. GVWR as well as with engines up to 440 ft. lbs. of torque.

However, the 4L85 was primarily designed for automobiles that weigh up to 16,500 lbs. GVWR as well as with engines up to 460 ft. lbs. of torque. This transmission has an incredible towing capacity as it was up-rated to 22,000 lbs.

The 4L80E series requires a shifter with a 7-position quadrant: P, R, N, OD, D, 2, 1. The torque converter on this automatic transmission is a fluid turbine drive, much like those found on its predecessors, e.g., the 700R4, 4L60, TH350C.

The 4L80E also comes with a lock-up pressure plate for direct, mechanically-coupled driving from the engine crank. It is 26¼ inches long and boasts a 310mm torque converter.

Applications of the Transmission

The 4L80E automatic transmission has several applications, such as:

  • Speed-sensing
  • Transfer case adaptability
  • Jeep conversions
  • Engine compatibility

Final Thoughts

By now, you already know that the 4L80E automatic transmission is intelligently designed to meet transmission challenges. This implemented automatic transmission from the legendary General Motors has an extraordinary record in conversion situations and will always leave you super-impressed.

545RFE Transmission Specs and Schematic

545RFE Transmission - Gearstar Performance Transmissions

The 545RFE transmission is an electronically controlled unit that was great for its time until it was replaced bu the 65RFE and 66RFE. Read below for specs and more information.

The automobile universe witnessed the introduction of the 545RFE/45RFE transmission in 1999 Chrysler models. The transmission was a perfect fit for 2-wheel-drive vehicles as well as all-wheel-drive automobiles. 

The 545RFE transmission, formerly known as the 45RFE – introduced and popularly seen in the Jeep Grand Cherokee of 1999 – is highly notable for its three planetary gearsets instead of 2 planetary gearsets commonly used in a 4-speed automatic.

The 545RFE also features the following:

  • Three multiple disc holding clutches
  • Three multiple disc input clutches
  • A dual internal filter system (one filter for the fluid cooler return system and the other primary filter for transmission sump)

The 545RFE transmission, based primarily on the 45RFE automatic, was used extensively in Chrysler’s entire fleet of rear-wheel heavy-duty trucks, except for coupes and sedans.

545RFE Transmission: Specs

But back in 1998, Chrysler has introduced the 45RFE in the 1999 WJ Jeep Grand Cherokee. This transmission was paired remarkably well with the 4.7 L PowerTech V8 engine. The ’45’ refers to its torque rating, i.e., ‘5,’ while ‘4’ represents the number of forward gears. ‘RFE’ refers to the ‘rear-wheel-drive application and full electronic controls.’

But by 2001, the 545RFE transmission was produced due to a taller, extra overdrive ratio and programming changes. The new transmission had a standard axle ratio that resulted in 2000 revolutions per minute at the engine, allowing you to cruise at 110 km/h (70 miles per hour).

The 545RFE transmission found its way to several SUV and truck applications from 2001 to 2012 with Jeep Commander and Jeep Grand Cherokee models that sport higher output Hemi engines. It could also be found in several Dodge Durango models within this period.

Although the engine yield was 200 rpm less than the 45RFE, the outcome was a considerable decrease in noise and fuel consumption. Now, the 545RFE transmission had six forward speeds and one reserved for kickdowns.

The engineering of the 545RFE transmission closely resembles that of the solid Torquefiles or an up-to-date version. The 545RFE transmission had a tall 3.00:1 first gear for initial acceleration.

The reverse was designed to be equal to first gear to accommodate heavy loads easily. When the 545RFE transmission was launched, it had the broadest range of gear ratios within its class. Even the factory where the transmission was made was also brand-new.

According to experts, the 545RFE comes with 2 overdrive gears. These are relatively close to each other due to the available size. The top 0.67:1 was probably chosen since that was the largest one that could easily fit without enlarging the transmission, making it too big for the organization’s automobiles.

To be clear, the following are the 545RFE gear ratios:

First gear – 3.00:1

Second gear – 1.67:1

Second gear (Prime) – 1.50:1

Third gear – 1.00:1

Fourth gear – 0.75:1

Fifth gear – 0.67:1

Reverse – 3.00:1

The capacity of the 545RFE transmission is 10.5-11 l, while the fluid type is Dexron 3-6 or MOPAR +4.

Some models with the ‘Tow/Haul’ mode were able to make faster shifts to cut wear on the 545RFE transmission. This considerably minimized the search for gear by holding the lower gears for extended periods. It was also possible to choose lower gears when traveling downhill to boost engine braking.

The computer-controlled 545RFE transmission comes in a burnished, one-piece die-cast aluminum casing. The casing was ribbed to increase torsional rigidity. Early transmission units took up to 6.6 quarters (6.2 liters) of ATF+3 fluid, while later versions took the same amount of ATF+4 fluid.

The gear ratios were designed to provide reserve torque as the transmission was highly suitable for the large torque band of the VM 2.8 diesel, Hemi V8, 4.7 V8, and 3.7 V6.

However, in 2009, the computer was programmed so that drivers could easily select the highest gear the 545RFE transmission would shift to. This made it easier for vehicles with this transmission to tow other vehicles, climb hills, and descend without any issues.

Common Issues with the 545RFE transmission

Here are some of the common problems that the 545RFE transmission showcases:

Solenoid Pack

Since the this transmission has zero transmission bands, the 545RFE – which is electronically controlled – relies heavily on a solenoid switch pack to efficiently direct fluid to the proper clutch pack for smooth gear engagement.

If something goes wrong and the solenoid pack becomes defective, there will be no gear engagement, failure to engage overdrive, stalling of the engine seamlessly, and ‘limp mode.’


This is another common challenge when moving parts within the transmission generate much more friction heat than the ATF can siphon away.

The primary cause of this problem involves the towing of heavy loads, multiple shifting of transmission on mountain roads, and driving in heavy stop/go traffic.

Delayed and Slipping Gear Engagement

The 545RFE transmission pump comes with a bit of a valve mechanism, which controls the fluid pressure that the torque converter transfers.

If the valve mechanism becomes faulty, you will experience significantly delayed gear engagement, stalling, torque converter/transmission overheating, reduced fuel economy, and slipping.

Harsh or Delayed 3-4 or 4-5 Shifts

Users of this transmission may experience a severe or unusual delay of 3-4 or 4-5 gear change. In such instances, it appears as if the transmission is reluctant to go into that specific gear.

This problem is linked to valve body issues in which the material used for making one of the check balls has somehow broken down so severely that fluid easily gets past and engages the underdrive clutch during the shifts.

The only way to solve this problem will be to install an upgraded #2 check ball made of a tougher material.

Four and five-speed automatic transmissions have up to 90 percent of interchangeable parts, and this makes it easy to perform repairs. The 545RFE transmission is reliable and highly durable, making serious damage a scarce thing. 

Although it was originally developed and designed to be used by heavy-duty engines, it is very compact. The use of highly active electronic control systems significantly reduced the valve body and drive shafts. 

Differences Between the 45RFE and 545RFE Transmission

The 45RFE and the 545RFE transmissions are mechanically identical. The notable difference comes down to software.

The 545RFE transmission has an electronically activated fifth gear. You will also notice that the unit control module and solenoid pack is different in both transmissions.


This transmission was excellent in its heydays. It was an electronically controlled unit that Chrysler produced and used extensively until it was replaced by the 65RFE and 66RFE automatic transmissions. For information on other performance transmissions and torque converters, contact us today.

The 4L70E Transmission: Up Close and Personal

4L70E Transmission - Gearstar

The 4L70E automatic transmission is undoubtedly a workhorse gear mechanism that offers more excellent reliability and a good deal more power. Read on for specs and more information.

The 4L70E is a 4-speed automatic GM transmission with up to 5 gears, including reverse. The 4th gear of the 4L70E is a .70 overdrive. It also shares the same basic design – and case – with the 4L60E and the 4L65E. This 4-speed automatic transmission is designed with considerably lightened materials to support much better fuel efficiency, electronically-controlled shifting, and four speeds. It is the last iteration of a unique design launched long ago, starting with the 700R4.

Here are the specs of the 4L70E:

  • Production: 1992 – Present time
  • Manufacturer: General Motors (GM)
  • Torque Converter Lock: Yes
  • RPO Code: M70
  • Overdrive: Yes

Outer Case Material

  • Aluminum + 2 removable bellhousing
  • Controlled by Computer: Yes, via the engine ECU.

Gear ratios are as follows:

  • First gear: 3.06
  • Second gear: 1.62
  • Third gear: 1.00
  • Fourth gear: 0.70
  • Reverse gear: 2.29

The 4L70E automatic transmission weighs approximately 133 lbs. dry.

The Unique Differences Between the 4L70E and 4L60E

There are several differences between the 4L70E and the 4L60E. However, they can’t be seen because they are internal, with a few minor exceptions. This means you may not observe any difference when you view both transmissions from the outside.

For instance, the output shaft is different, and the 4L70E now bears an input shaft speed sensor. 

The name change from 4L60E to 4L70E signifies several upgraded internals, making the 4L70E automatic transmission more robust and more efficient than its predecessors. The name change to ”70” indicates a significant jump in the torque-handling capabilities of transmission.

Here are some of the few – but significant – structural improvements that have been made to the 4L70E, which has boosted its reliability and efficiency over its predecessors:

  1. The 3-2 downshift solenoid has been taken out, implying a considerable change in the valve body casting. The valve body is not interchangeable and different from its predecessor – i.e., the 4L60E – since the 3-2 solenoid location has been cast shut.
  2. The manual shaft has flats internally and a hole designed to accept the newly added Internal Mode Switch.
  3. The schematics, as well as internal wiring, have been changed entirely. The connector pin in this automatic transmission is far different from the ones found in its predecessors.
  4. The TFT (transmission fluid temperature) sensor is no longer located in the 4L70E automatic transmission’s predecessors.
  5. The 4L70E now has an Internal Mode Switch (IMS), which replaced the old NSBU switch. The NSBU was external, while the IMS was internal.

Other minor changes include the total removal of the Parking rod and pressure switch. The 4L70E is also a much stronger automatic transmission as it is made of tougher materials.

The 4L70E and the 4L60E transmissions look very much alike, except for the differences in the internals. Swapping parts from one to the other is a very poor decision, primarily if you don’t ensure that those components share the same GM Parts number.

In other words, don’t even think about it. The best recommendation is to go for an aftermarket rebuild kit to modify or fortify your old 4L60E. You can’t convert the 4L60E to 4L70E.

How to Tell Two Transmissions Apart Without Opening Them Up

If you are looking for a particular transmission in stock GM automobiles, you can tell the 4L70E apart from the 4L65E without opening up both. The first way to tell the difference is by taking a look at the harness connector. The 4L70E transmission has a neon blue or black harness connector.

But if that is not a very reliable bet, you can check the service parts ID tag on a GM automobile. An ”M70” symbol should be o the tag, especially if the automobile’s stock transmission is a 4L70E. 

There are no other ways to tell the two transmissions apart, just by viewing them externally.

Can the 4L70E Replace the 4L60E Transmission?

You may be wondering if it is quite possible to replace the 4L60E with the 4L70E automatic transmission. Yes, it is possible: the 4L70E will bolt right in with some minor exceptions.

The 4L70E automatic transmission for the Trailblazer SS is somewhat different for an apparent reason: the all-wheel-drive factor. The torque converter for both transmissions is the same. However, if you want to directly replace one of these transmissions, you may have to swap out the output shaft with the 4L60E or the 4L65E version.

Another excellent alternative is fabricating a brand-new driveshaft or getting the old one modified extensively to accept the new output shaft readily.

The 4L70E Automatic Transmission: Built for Toughness

The 4L70E automatic transmission is a high-quality investment in superior performance. And installing it is not a plug-and-play business. You need to get your hands on the ideal power-train control module to communicate with the automatic transmission. In a few cases, you may have no choice but to re-pin the wiring harness.

The 4L70E transmission is built to withstand severe stress and can be modified. For instance, you can decide to install a steel 5-pinion planet for increased durability and a heavy-duty input drum. Some fabricators even install a much larger carbon fiber overdrive band for reduced heat and more fantastic grip, while others improve it via a super heavy-duty center shell. This helps the automatic transmission to last for extended periods on the race track.

Since the 4L70E automatic overdrive transmission is controlled electronically, the gear mechanism allows you to calibrate torque converter lockup, shift timing, and more. This makes the 4L70E much more versatile than the older throttle valve cable predecessor, the GM 4L60s.

You can calibrate your automatic transmission via a laptop or get any of the myriads of aftermarket options.

If you are looking for a pretty solid GM transmission within the 650 HP and ft./lbs. Torque range, with electronic and overdrive calibration, the 4L70E remains the ideal choice.

The Takeaway

The 4L70E automatic transmission is undoubtedly a workhorse gear mechanism that offers more excellent reliability and a good deal more power. Upgrading to the 4L70E automatic transmission is your best bet if you are looking for or require a transmission capable of working up beyond the realm of 425 ft./lbs. of torque and 450 HP and below the 650 HP and ft./lbs. of torque range.

Can Low Transmission Fluid Reduce Engine Power?

Can Low Transmission Fluid Reduce Engine Power? - Gearstar Performance Transmissions

From getting to work to getting the kids to school to getting to your best friend’s house, you depend on your vehicle in a vast number of ways. To have a smooth run of your vehicle, all the entire architecture and engine mechanism must perform optimally. To start with, the engine – which is the heart and also a delicate part of the vehicle, must be in a healthy state all times.

How do you feel when you have your foot on the accelerator and you there is a drag in the movement of the vehicle? Frustrating. Transmission could be responsible. In days-gone-by of ancient vehicles, mere changing of the spark plugs, plug wires or even the carburetor would bring about a drastic change in the ‘drag’ movement. In modern vehicles where sensors are embedded, there are all kinds of culprits behind your car reluctance to accelerate.

You could be confused how transmission and/ transmission fluid is very important to vehicle’s engines. Here is why. But before getting to know the importance of a transmission fluid, this is what transmission means. Transmission refers to a gearbox that makes use of gear and gear trains to provide speed and torque conversions from a rotating power source, the engine, to another device – wheels.

Transmission fluid, on the other hand, is used to lubricate the components of a car’s transmission for optimum performance. If you have a faulty transmission, it will affect the smooth run of your engine which in turn makes you frustrated. In a situation where there is leakage or low transmission fluid, the engine would not provide maximum speed your vehicle.

What Is Engine Power?

To fully understand how engine works, knowing the power your engine can produce is important. Engine power is the amount of twisting force available at the crankshaft in the engine. The more torque you have, the more pulling power the engine has; hence, the force you feel when accelerating your vehicle.

The torque measurement provides an indication of how fast the engine will be able to move your vehicle’s weight. When driving and you have “engine power induced” light on, most times, it is the transmission losing its fluid. Also, the “check engine” light may pop on. Do not panic yet. Remain calm when driving your vehicle.

Ideally, when these lights come on, they mean your vehicle’s performance has been reduced to avoid damaging and wearing off the engine. And most modern cars are with series of sensors, which makes the electronic control unit to trigger the Reduced Power Mode after it has detected a system failure in the engine.

What Triggers the “Reduced Engine Power” Warning Light?

There are lots of reasons why your reduced engine light is on and you may be confused on how to make it go off. However, one of the most common causes of this problem is a fault with your electronic throttle actuator system. Modern cars utilize this in the stead of a tradition mechanical throttle body. In a throttle actuator control system, the Engine Control Unit masterminds two accelerator position sensors to determine your desire to accelerate. The device calculates the appropriate throttle response from two throttle position sensors.

Once it has the necessary information from the sensors, the Engine Control Unit uses an actuator motor to maneuver the throttle, thus controlling airflow into your vehicle’s engine. Any problem with your throttle actuator control system can easily trigger the “reduced engine power” warning light on the dashboard of your vehicle. For quick instance, the problem could be one of the vehicle’s sensors, the throttle body or even the accelerator pedal assembly.

Solutions to Reduced Engine Power Light

When you start your vehicle and you notice the Reduced Engine Power light is on, it is very much advisable not to drive. And if you are already at top speed on the highway, it is expected of you to visit a technician immediately. When you notice the light is off, the next thing is for you to scan your vehicle.

Sometimes, error codes and faults that occur are stored within the systems of your vehicle even if the scan occurs after the light goes off. In days-gone-by, older vehicles do not have computer systems which makes detecting fault more difficult. And finding these faults could be very expensive as well.

How do you fix this problem; reduced engine power light? Before driving to the mechanic or a technician, you could handle this yourself. If you drive a reduced engine power car, it could cause more problems before you get to the mechanic that will have your vehicle fixed. Here are the simple steps you can take:

1. Replace the Air Flow Sensor

There are couple of ways to detect if your vehicle’s air sensor is not working properly. When you start the engine, open the hood or bonnet. Try to locate the air flow sensor and tap severally. If the engine falters slightly, the air flow is dirty. Alternatively, stop the engine and disconnect the sensor.

Start the engine afterwards. The engine will sense the removal of the air flow sensor and will go into a back-up running mode. This is a simple fault with a pretty simple fix. Replacing the air flow sensor is the best alternate when you discover it is dirty and enjoy a return to your standard engine power!

2. Replace Air Filter

Another step in having a healthier engine is to make sure you have a clean air filter in perfect working condition. In almost all modern cars, the air filter is located in a rectangular box. It is placed to one side of the engine block just near the fender. Remove the filter itself and have a check under a light.

If no light or very little light comes through, that means the air filter is clogged and must be replaced immediately. When engine response to distorted conditions begins, transmission fluid is one of the major things to replace immediately. Hence, the reduction in engine power which would make the engine wear and tear in no time.