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February 2020

In Transmission & Drivetrain

4R70W Transmission-Swapped Fourth-Gen Mustang?

4R70W Transmission-Swapped Fourth-Gen Mustang? - Gearstar

The fourth generation Ford Mustang can be made faster and more reliable by carrying out some performance upgrades instead of adding more power. It may involve installing a performance automatic 4R70W transmission in a bid to change the stock unit that came with the vehicle.

While a stock transmission comes directly out of the manufacturer’s warehouse, it may be unable to handle your need for speed. The latter can be tied to the Two Valve it features, which may leave the car struggling to get enough RPM (Revolutions per minute). Remember, if it gets enough RPM without struggling to, it takes it one step closer to being a faster ride.

Accordingly, the modifications or boost you can give the Mustang will provide a nose that is significantly higher than what a stock Two Valve can. The aim is to meet or exceed the original equipment manufacturer’s (OEM) measured standards.

But first…

What Is a 4R70W Transmission?

The 4R70W was launched as an improved version of the AOD-E transmission. And compared to the AOD-E, the 1st and 2nd gear ratios of the 4R70-W are numerically higher. This resulted in:

    • Better gearset strength
    • Lower fuel consumption
    • Better take-off acceleration
    • Better mechanical advantage

This Ford transmission is also an upgrade to the AOD, a 4-speed automatic overdrive transmission, aimed at tackling fuel efficiency issues. Upon its launch, the transmission featured a “wide ratio” gear set, however, a mechanical diode replaced its intermediate one-way clutch in 1998.

Often times, upgrades to the Mustangs with the 4R70W transmission are made possible using 4.10 rear end gears, shift kits, and a performance torque converter.

4R70W Transmission Specs

The 4R70W transmission specs are:

    • Transmission: Ford 4R70W
    • Predecessor: Ford AODE
    • Type: 4-speed overdrive automatic transmission
    • Wide gear ratio
    • Rear-wheel drive
    • Case Material: Aluminum
    • Max Input Torque: ~ 516 lb-ft (700 n-m)
    • ATF Type/Spec: MERCON V ATF (Motorcraft XT-5-QMC)
    • Transmission Filter: Motorcraft FT105

Gear ratios:

    • First: 2.84 :1
    • Second: 1.55 :1
    • Third: 1.00 :1
    • Overdrive: 0.70 :1
    • Reverse: 2.32 :1

4R70W Transmission-Infused Vehicles

Cars that used the 4R70W transmission include:

    • Ford F-150 Series pick-up trucks, E-150 Series vans, Expeditions, Explorers, Crown Victorias, Thunderbirds, and Mustangs
    • Lincoln Town Cars and Mark VIIIs
    • Mercury Grand Marquis, Cougars, Mountaineers and Marauders

Specifically, the years this transmission was used are:

    • 1993–1998 Lincoln Mark VIII
    • 1993–2003 Ford F-Series
    • 1994–1997 Ford Thunderbird
    • 1995–2004 Ford Crown Victoria
    • 1996–2001 Ford Explorer
    • 1993–2004 Lincoln Town Car
    • 1994–1997 Mercury Cougar
    • 1995–2004 Mercury Grand Marquis
    • 2003 Mercury Marauder
    • 1997–2004 Ford Expedition
    • 1997–2001 Mercury Mountaineer
    • 1996–2004 Ford Mustang
    • 2004–2005 Rover 75 V8

On the other hand, the 4R70W was not the only transmission for Mustangs.

This is because Ford had launched a range of transmissions since 1979 for Mustangs, and as such, you can find a wide variety of these transmissions. Other models include:

    • C4 Transmission
    • Automatic Overdrive or AOD Transmission
    • AOD-E Transmission
    • 4R75W Transmission
    • 5R55S Transmission

How to Boost Performance in a 4th Generation Mustang

A performance automatic 4R70W transmission can be used to boost the performance of a fourth generation Mustang. This is because a well-built automatic transmission and a torque converter with the right specs can give you car a good boost.

In that regard, this boost can be made possible by replacing the stock automatic-equipped Two Valves in the ride. Why is that?

The stock transmission is not known to offer an out-this-world performance due to the fact that a stock converter does not really perform to its best when it lacks low-rpm torque. In the same vein, the slushy shifts it makes shows that it is spending more time between gears rather than driving forward.

Nonetheless, some stock 4R70W-equipped light bolt-on New Edge GTs move speedily and even cover the quarter-mile in the low 15-second to high 14-second range. Much more, this performance is carried out seamlessly.

Accordingly, what you need to begin, is the right aftermarket parts to bring out their best performance. It all begins with a transmission upgrade.

Advantages of a 4R70W Transmission Upgrade

An automatic transmission upgrade can help with your ride’s performance, hence, it is a good place to start instead of adding more power. Here are some benefits that can be obtained from this transmission upgrade:

    • An upgrade will enable the car to shift gears faster and hold more power.
    • The performance converter will be able to move the car into the powerband sooner.
    • The upgraded components will be able to withstand the converter being locked under WOT.

Consequently, adding more power is not the most ideal solution since a good number of stock automatics tend to fail in short order once more power has been added. It could mean more problems in the long run, but it can be avoided by starting from the basics through a transmission upgrade.

4R70W Transmission Problems

Asides from upgrading your transmission to get more speed, it can help to improve its reliability. This is because there are certain 4R70W transmission problems that are prevalent with the stock transmission. For starters, the stock 4R70W transmission was susceptible to the following issues:

    • Harsh 2-3 shift
    • Delay in lock-up
    • Loss of second gear and third gear
    • Loss of fourth gear and forward gears
    • An intermediate clutch failure
    • Delay in reverse or shudder in reverse
    • Leaking of the front seal or pump noise

The Bottom Line

The 4R70W is a good transmission, however, it can be made to perform even better in a fourth generation Ford Mustang. In this case, the usual route of adding more power is not employed, instead, a transmission upgrade is carried out to ensure that whether you’re out for drag racing or performance driving, you can get good speed.

What’s more, an upgrade from the stock transmission will eliminate certain issues that were prevalent in it. These issues include loss in gears, delays in lockup, clutch failure, and many others. Once each of these is eliminated, it can go a long way to improve the reliability of your transmission and also help it to offer more power boost.

In Transmission & Drivetrain

Overview of the GM TH400 Transmission

The GM TH400 Transmission: An Overview - Gearstar

 The TH400 or Turbo 400 is a good transmission that was used in several cars years ago. This popular transmission was found in GM’s cars, as well as, Rolls-Royces, Jeeps, Jaguars, Ferraris, etc. The TH400’s high-level of adoption could be tied to its remarkable features, and it proved that people can once again rely on GM transmissions.

But what were these features sported by this durable and legendary transmission, and generally, what set it apart from other transmissions from this manufacturer? An overview of the TH400 transmission will give you a better idea. Read on to find out!

 

The GM TH400 Transmission

The GM TH400 transmission is a three-speed automatic transmission that was longitudinally positioned behind the engine. This placement is aimed at providing the best power ratio and durability for rear-wheel drive. The TH400 has been rated at 450 ft. lbs. of input torque, nonetheless, aftermarket designs that have been modified may go beyond that rating.

 

History of the TH400 Transmission

The TH400 was launched by General Motors in 1964, as a replacement to the ST300 2-speed automatic transmission. It was used in a wide range of vehicles, hence, it was not just exclusive to GM cars.

Upon its launch, the TH400 was evident in Buicks and Cadillacs, and a year later, it was used in Chevrolet and Oldsmobile cars. Buick, Olds, and Cadillacs that were later launched between 1965-1967 also featured the transmission but with an innovative variable-pitch stator. This stator helped to vary the torque converter’s characteristics, and you can tell a car has this stator by the two-prong plug on the case.

In the 1970s, the TH400 was used in heavier-duty GM trucks and it was available in 2wd and 4wd configurations. The naming of the TH400 was changed to 3L80 (3-speeds, Longitudinally positioned, 8000 lbs. GVW or Gross Vehicle Weight) in 1990 to make it easier for buyers to identify the transmission.

The change in naming does not come as surprise since some GM transmissions were also renamed (for example the 700R4 to 4L60). Around the same time when the TH400’s name was changed, an overdrive version called the 4L80-E was launched.

This is an electronically controlled transmission that is still being produced and used in a range of heavy-duty GM and military cars/trucks. Generally, here’s a list of cars that used the TH400 transmission:

    • 1965-1967, 327 V8 (Rambler/AMC)
    • 1968-1971, 350 V8 (Buick)
    • 1969-1972, 225 V6 (Buick)
    • 1972-1975, 232 I6 (AMC)
    • 1975-1979, 258 I6 (AMC)
    • 1972-1979, 304 V8 (AMC)
    • 1972-1979, 360 V8 (AMC)
    • 1974-1975, 401 V8 (AMC)
    • GM
    • Jaguar
    • Ferrari
    • Rolls-Royce

 

Features of the TH400 Transmission

The features of the TH400 Transmission enabled it to provide improved performance over previous transmissions. It was also durable, and these characteristics can be tied to the following:

    • Aluminum and iron construction.
    • Weighs 135 pounds without fluid.
    • Bell housing integrated into the transmission.
    • First gear: 2.48:1, Reverse gear: 2.08:1, and third gear is an even 1 to 1.
    • Came with three tail shaft lengths.

 

Turbo 400 Transmission Identification

The Turbo 400 transmission can be identified in the following ways:

1. External Build

The TH400 transmission comes with a case made of cast aluminum alloy to give it strength and durability. The case is very smooth and its length sits at length of 24-3/8″ long. This TH400 is the largest of the common GM automatic transmissions, however, the transmission still maintains a compact design.

There is a hex bolt pattern on the rear mounting face of the transmission and the ribs run forward longitudinally. In line with that, the fluid pan has an irregular shape.

2. Variants of the TH400

There are two variants of the TH400, and these are the TH375 and TH475. The TH375 was used in smaller displacement cars between 1972-1976. In contrast, the TH475 was used in larger trucks from 1971 since it is an extra-heavy-duty version. One can easily different either these variants apart by looking out for the “375-THM” designation cast on the bottom of the tail housing.

TH350 vs. TH400

A simple way to differentiate them is to check the kick-down mechanism. The TH400 transmission takes advantage of an electrical slide switch controlled by the throttle linkage. On the other hand, the TH350 uses a mechanical cable kick-down that is connected to the throttle linkage. Despite the difference, the TH400 is considered the heavy-duty version of the Turbo-Hydramatic 350.

 

Transfer Case of the TH400 Transmission

The TH400 can easily be adapted for use in most Jeeps longer than CJ5s, and as such, it is an excellent conversion transmission. Whether it’s the 2wd and 4wd versions of the Turbo 400, either of these can be used. Nonetheless, the 1976-1979 AMC case is similar to that of the TH400’s, from the collar of the case and back, however,  it is tilted about four degrees.

 

Engine Compatibility and Adaptability

The engine compatibility and adaptability of the TH400 transmission include:

1. AMC/Mopar Jeep

The earliest Turbo 400s in Jeeps featured a factory adapter plate, whereas older AMC versions came with a dedicated AMC style case. It is entirely possible to make the Chevy 400  compatible in the AMC I6 & V8 engines. As an upgrade of this nature can result in a more enhanced Jeep powertrain over 727, 999.

2. Chevrolet

The front face of the TH400 is compatible with the Chevy 90 degree “Small Block” or the “Big Block” patterned engines.

3. Buick / Olsmobile / Pontiac / Cadillac

The TH400 is compatible in Buick engines especially when you use a Buick V8 or V6 version of the transmission.

 

Common TH400 Problems

The TH400 may have offered improved performance over its predecessor, the ST300, but it still came with its own problems. Notable among this is an early shift and less efficiency when the engine revs high. The latter occurs when the kick-down switch, responsible for shifting between gears and maintaining maximum RPMs, stops working. The switch would’ve helped in, efficient power usage.

On the other hand, the cause of this problem can be tied to the wrong placement of the vacuum hard-line, moving from the intake manifold with a pliable rubber line. The heat generated by the engine and transmission leads to the deformity of the rubber, thereby failing to hold the pressure properly. Another problem of the TH400 is the possibility for its transmission fluid to leak gradually into the hose if the seal is not fixed properly.

 

The Bottom Line

An overview of the TH400 transmission shows it is a durable transmission that can give a good performance. The TH400 was used in a wide range of cars from GM as well as other manufacturers. Interestingly, the transmission can be adapted for use in several engines today. In the end, whether it’s a new or aftermarket TH400 you settle for, you are bound to get the full benefits offered by this transmission.

 

In Transmission & Drivetrain

Torque Talk: Benefits of Installing an Aftermarket Torque Converter

Benefits of Installing an Aftermarket Torque Converter - Gearstar

If you own a car with an automatic transmission, chances that you’ve heard the term “torque” or “torque converter” from time to time. But what do all these mean and how does a torque converter work? And most importantly, are there any benefits you stand to gain from installing an aftermarket torque converter? Let’s take a quick look.

 

What Is a Torque Converter?

A torque converter is one of the major components in an automatic transmission, and it can be likened to a mechanical clutch in a manual transmission. As a type of fluid coupling, a torque converter transfers rotating power from a prime mover to a rotating driven load. The latter helps to connect the power source to the load in an automatic transmission.

Furthermore, this unit is located between the transmission and the engine flexplate – And it enables the engine to run while the car is stationary, but transfers power once the car starts moving. An aftermarket torque converter, however, is a converter that presents as a spare part.

 

Internal Components of Torque Converters

There are three main internal components in the torque converter that aids in its operation. These components include a pump, turbine, and stator. There is also the transmission fluid that moves through these components.

1. Pump

A converter’s housing connects to the engine’s flywheel, whereas the fins of the pump are links to the housing. This pump spins and pushes fluid outwards; hence, it is a centrifugal pump. The operation of the pump helps to create a vacuum that attracts more fluid towards the center, which then enters the turbine.

2. Turbine

The turbine is connected to the transmission through the output shaft, and the turbine’s spinning causes the transmission to move the car. Once fluid exits the turbine, it moves in a direction opposite to that of the engine and the pump.

3. Stator

The stator is located in the middle of the torque converter and it helps to redirect fluid before it re-enters the pump. The stator is placed on a fixed shaft, even though it has an internal one-way clutch to enable it freewheel at certain operating speeds.

 

How Does a Torque Converter Work?

There are three stages of operation evident in a torque converter and these are stall, acceleration, and coupling. Let’s take a closer look at each.

1. Stall

Stalling is when the turbine cannot rotate even after the prime mover has applied power to the impeller. A real-life scenario is when a driver puts the car’s transmission in gear, and at the same time, applies brakes continuously to prevent the car from moving.

What’s more, sufficient input power applied helps the torque converter to produce maximum torque multiplication – and the resulting multiplication is referred to as stall ratio. This stage of operation usually lasts briefly when the load starts to move initially since there will be a significant difference between the pump and turbine speed.

How to Check Your a Converter’s Stall Speed

One way to check a converter’s stall speed is to place the vehicle in Drive and press on the brake firmly – the throttle can be depressed fully for some seconds. The maximum RPM displayed is the stall speed of the vehicle’s converter.

What may be evident, is the tires spinning, due to the fact that the brake system may not be able to hold the engine back. The latter is known as brake stall speed and it is lower than the true stall speed.

2. Acceleration

In a situation where the load is accelerating but there is a large difference between the impeller and turbine speed, the torque converter will produce torque multiplication that is lesser compared to what would’ve been attainable under stall conditions. Nonetheless, the actual difference between the pump and the turbine speed will determine the amount of multiplication that is produced.

3. Coupling

Coupling is a stage of operation where the lock-up clutch is applied, which brings about fuel economy. Here, the turbine has achieved approximately 90 percent of the impeller’s speed. Also, torque multiplication is no longer evident and the torque converter’s operation can be likened to that of a simple fluid coupling.

 

Benefits of Aftermarket Torque Converters

There are several benefits of a torque converter, and some of these are:

1. Multiplication of Torque

A torque converter performs differently from a regular fluid coupling.  The latter matches the rotational speed, however, it is unable to multiply torque. In contrast, a torque converter can multiply torque in cases where the output rotational speed is low to the extent that it allows the fluid from the curved vanes of the turbine to be deflected off the stator.

Moreover, this fluid deflection occurs while the stator is locked against its one-way clutch, thereby providing the equivalent of a reduction gear. Torque multiplication also occurs when there is a difference between input and output speed.

2. Slippage

Some torque converters are built with a “lockup” mechanism. What the lockup does, is to bind the engine to the transmission rigidly when their speeds are almost equivalent. This operation helps to prevent high levels of slippage, and loss of efficiency.

Also, this helps to eliminate wasted power and at the same time improve fuel efficiency as high as 65 percent. If there are continuous high levels of slippage, however, it could make it difficult for the converter to dissipate heat.

When this happens, it could damage the elastomer seals that are responsible for retaining fluid within the converter. As time goes on, the fluid inside the converter may leak completely, thereby causing it to stop working.

 

The Bottom Line

A torque converter is a useful fluid coupling in automatic transmissions given the range of benefits it offers. From its ability to multiply torque, to preventing slippage that will bring about performance efficiency.

Nevertheless, it is worth noting that several components including the impeller, stator, and turbine aid its operation. Likewise, the three stages of operation are what finally leads to the resultant benefits reaped from using even an aftermarket torque converter.

 

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