Transmissions ultimately determine how the output of an engine’s power is translated throughout the rest of the vehicle. A transmission is built to prioritize – and there are plenty of things to prioritize. Do we need speed? Power? Efficiency? Weight? Cost-effectiveness? Throughout the decades, automobile companies have come up with increasingly fine-tuned and advanced examples of this, working off older concepts and introducing new ones along the way, such as electronic control and fine-tuning. But when it comes to matching cost with performance on a Chevy, you can’t go wrong with an older, customized transmission. While there’s nothing wrong with refurbishing a classic muscle car with a new and improved Turbo 350, you’re more likely going to see cars from the 90s and beyond outfitted with the more modern set of 4L60s and 4L60Es – four-speed automatic transmissions that are basically descendants of the Turbo-Hydramatic 700R4, a powerhouse of a transmission. The 4L60E is an automatic transmission with electronic control (E), 4 forward gears (and 1 reverse), longitudinal rear-wheel drive, and a 6,000 lbs. maximum gross vehicle weight limit. Yet the 4L60E isn’t the only transmission of its kind produced by GM at the time. It began as the non-electronic 4L60, installed in most GM trucks (like the Pontiac) before the introduction of the 4L60E, and other transmissions include its successors the 4L65E and 4L70E for large heavy-duty trucks, and stronger transmissions built with different gear ratios for even larger vehicles, such as the 4L80E.
The 4R70W is a Ford transmission, and generally considered an evolution to the AODE, a transmission that it is often interchanged with. Both are improvements on the AOD, Ford’s first 4-speed automatic overdrive transmission, and its answer to the fuel efficiency issues first brought to light in America by the oil embargo of the 70s. Since then, improvements in technology and stringent regulations improving fuel efficiency and air quality have demanded better and better transmissions, while still providing opportunities for top notch performance, even if only through a few modifications. No stock transmission is perfect, but if you’re looking for a small-body Ford transmission with potential for insane performance and no need to mess with pesky throttle valve cables or old-school controls, then the 4R70W is a good place to start – but by no means the best place to end. Here’s a quick overview of the 4R70W, it’s relationship to other popular Ford transmissions, and a few things you should know about it, including its basic strengths, glaring weaknesses, and ways to improve on it and make it both more reliable and better for performance.
Quick Overview of Ford 4R70W TransmissonsIt was around the 70s that automobile manufacturers started coming out with better, more fuel-efficient cars. These sacrificed some of the performance and speed of the gas-guzzling large-displacement carbureted V8 models of the past, in exchange for the ability to go long and fast at a much lower cost. While overdrive and general fuel economy were considerations for decades before the oil embargo, it was the steep increase in gas prices introduced by that decade that drove a change into American car manufacturing. It was around then that Ford first produced the AOD, its 4-speed automatic overdrive transmission, in 1980. The AOD was new, for sure, but mostly incorporated old designs. It didn’t change much from the FMX 3-speed automatics, save for a direct overdrive, and still used the Ravigneaux gear train and other common FMX components. It’s dependable and sturdy due to the inclusion of many of these true-and-tried components, but it’s the additions that make the AOD a liability. With a rather frail overdrive band lacking in proper width, it’s not uncommon for it to wear down quickly versus its newer alternatives. In comes the AODE. This was Ford’s improvement on the AOD, complete with a new valve body and computer controls to replace the classic throttle valve function and AOD valve body. The AODE was introduced in 1991, known simply as the AOD Electronic Control. It featured a completely revamped valve body, torque controller, front pump assembly, and a single input shaft rather than the primary and intermediate shafts of the AOD.
Specs on the 4R70WBy 1993, an updated version of the AODE hit the market with a different name, although these two transmissions are mostly interchangeable. The 4R70W comes with:
- 4 forward speeds
- Rear-wheel drive
- 700 lb.-ft torque rating
- Wide gear ratio
- 1st gear: 2.84 (2.40)
- 2nd gear: 1.55 (1.47)
- 3rd gear: 1:1 (1:1)
- 4th gear: 0.70 (0.67)
So, Which Is Better?While the 4R70W is unquestionably better than its predecessors in many ways, that doesn’t always mean it’s the best option for you at the time. If you already have a stock AOD to begin with, there’s a lot you can do with some spare cash without having to invest in a completely new electronic transmission. While the 4R70W can be adapted even to older classic muscle cars, it does take a bit of work and a bit more cash than updating and reworking your stock AOD. The same goes for cars with the AODE in the 90s. The only time you might want to switch for the 4R70W is if you can afford it, and if you need the improvements.
Better Overdrive, Computer ControlThe main benefits of the AODE and 4R70W over their older version is the inclusion of a sturdier, wider overdrive band, better front pump, a solid input shaft, a switch from split-torque overdrive lock-up to the use of a locking torque converter, and finally, much improved pinpoint precision and control through computer-controlled components versus the oft clunky manual control given by a throttle valve function. Despite a thicker and improved valve body, the electronic AODs also come with a lighter case, built with aluminum rather than steel, improving weight and thus performance and fuel efficiency.
The Good, the Bad and the UglyThe 4R70W is a good transmission, but it has its pros and cons. Let’s look over some of its best qualities, and some of its faults and issues. For one, it has a much better and improved overdrive band. Despite being a newer transmission and having a completely different case, the 4R70W is still compatible with a vast number of Ford vehicles without too much reworking or adaptation. You can easily retrofit it into many classic muscle cars, giving older vehicles a much-needed boost in both efficiency and performance. However, as powerful as it is, be careful not to overload this transmission. There’s a limit to its torque and power, and knowing exactly what it can and can’t do is the difference between an overheated transmission and one that will last you for decades. That, and as with any other transmission, you still need to maintain it regularly.
A Diamond in the RoughStill, for all its merits and the improvements made upon the 4R70W after decades spent on feedback from the AOD and AODE, there are still flaws in the transmission that must be addressed through aftermarket improvements. A specialist in Ford transmissions can set you up with an improved 4R70W, with as much as 750hp, an improved torque controller, a much-needed improved cooler with a better GVW of 30,000, and countless reinforcements to improve durability, maximize performance in the long-run, and prevent some of the faults that eventually lead to complete transmission breakdowns in the future. Examples include an improved carbon fiber overdrive band, new pump assembly, higher capacity clutch, updated solenoids for better electronic functionality, and more. Be sure to only work with specialists who guarantee the quality of their transmission, and do their best to test the integrity of their work every time.
There’s no doubting the air of Americana around a classic 50s-70s GM ride. In the golden age of American automobile manufacturing, we turned building cars into an art form, and ever since it’s been an intrinsic part of our culture – but even in today’s age of hybrid vehicles, electric cars and fuel-efficient family minivans, anyone with the keys to a classic GM ride knows that there’s nothing that quite compares to riding behind the wheel of one of Detroit’s best. However, there are also few cars that compare when it comes to sheer fuel consumption. The 50s weren’t exactly known for extreme frugality, and fuel economy wasn’t on the mind of the average American automotive owner. Instead, we focused on speed, on style, performance. But then the oil crisis kicked in, and car owners quickly realized that they’d have to account for a steep increase in fuel prices. The result? We needed a new approach to fuel consumption, one that would emphasize a more frugal cruise. That’s where the popularity of overdrive came into play.
How Overdrive Works in an Automatic TransmissionOverdrive is when the car’s cruising speeds are maintained while the engine’s RPM are reduced, leading to better fuel efficiency at the cost of performance, or speed. This is done through a faster output speed than input speed, through a specific gear set. This allows you to travel long distances with a much lower fuel cost, and various different automatic transmissions offer different levels of fuel efficiency. By “over-gearing” and sacrificing the car’s top-speed at that point in time for a lower RPM, you end up burning less fuel while maintaining cruising speed on a flat road. This can’t typically be done on rough or uphill terrain, as the car loses power in overdrive. Typically, when achieving top speed, a car needs to continuously produce more power to match the increase in air resistance produced by an increase in speed. The ideal gear ratio for speed is the one that matches travel speed with engine speed. But when fuel efficiency becomes the goal, another set of gears is needed to reduce engine RPM but maintain cruising speeds. This, in essence, is the overdrive.
Evolution of the Automatic Overdrive TransmissionOverdrive transmissions in North America were an option in pre-automatic transmissions as far back as the 50s, but it wasn’t until the corporate average fuel economy legislation in 1975 that basically every single American transmission was built to include overdrive. If you’re planning on riding your classic GM, then an automatic overdrive transmission (AOD) is a basic necessity unless you like watching your tank evaporate like a puddle on a blazing hot day.
Choosing the Right Overdrive Swap for Your GMWhen the oil crisis called for new transmissions with a focus on fuel efficiency and compatibility with most of the existing vehicles on the market, GM and other car manufacturers got to work on implementing the overdrive. Throughout the 80s and beyond, automatic overdrive transmissions became a norm on most GM vehicles, from classic Chevy pickup trucks to muscle cars. Choosing among GM's selection of overdrive transmissions from back in the day is a matter of two things: compatibility and expectations. Stock automatic transmissions are only built to handle a certain amount of torque and horsepower, and trying to push one beyond its limits is a surefire way to slipping gears, burning through your overdrive and making a mess of things. Here are a few good GM AODs, and some things to keep in mind when choosing among them.
700R4The 700R4 is widely considered the best 4-speed automatic overdrive transmission out there, and can be seen as one of GM's best and most reliable AOD transmissions. It first hit the road in the early 80s as a replacement to the TH350 (Turbo-Hydramatic), although this early version doesn’t compare to later 700R4s typically installed in Chevy vehicles before 1993, when it was replaced with the electronic 4L60E. While it’s a solid transmission, it can be easily tweaked and built for better performance and much better durability. Some issues commonly found in the 700R4 include its often faulty or frail TV cable, and a tendency to overheat. A better cooler, a torque controller and a few aftermarket bits and pieces can turn this into an extremely solid piece of engineering.
200-4RThe 200 4R is possibly the ideal transmission for early GM vehicles, due to compatibility and a comparable strength to the 700R4. Seriously, this thing will bolt in nearly every Chevy chassis on the market, with very little necessary modification. Like with the 700R4, a TCI kit or a custom job by any trusted transmission expert can make this tranny run much better, with a repositioned TV cable and torque controller being some minimum additions to consider. However, with heavier modifications, you can take this thing even further.
4L60E, 4L65E, 4L80E & 4L85EGM's later overdrive transmissions included the 4L60E, 4L65E, 4L70E, 4L80E and 4L85E. Each of these were a continuation of the Turbo 400 and Turbo 700R4, built for rear-wheel high performance. The differences largely lie between the 4L60E and the 4L80E. Key differences are size and performance. It wouldn’t make much sense to stick a 4L80E into anything smaller than a Chevy truck, especially with the considerable price difference between these two transmissions. However, if you’re going with a stock 4L60E but have a vehicle capable of going pas 300 horsepower, you’re liable to see that tranny break. A custom 4L60E will get the job done, as will a stock 4L80E. These are electronic overdrive transmissions, which makes them trickier to install in older vehicles, but not impossible. The alternative is to opt for the older 4L60 transmission, which is not as powerful, but doesn’t include electronic shift controls. That may be more up your alley if you prefer manual shift, too.
Overdrive Transmission InstallIf you’ve got the equipment and the experience, then installing a new transmission is just a matter of getting all the right bits and pieces. For that, the Internet is an amazing source of aftermarket parts, reviews and more. But if you’re looking for someone to get the job done for you, you’ll need a more experienced crew. Instead of a stock overdrive transmission installed straight into your ride, consider a stronger, performance-based custom tranny. Some select performance transmission experts have the skill and the reputation to work on some of GM’s finest old-school AODs, and turn an old stock transmission into a power house ready to put in work on the race track.
The motoring world is full of competition, both on and off the track. If people aren't competing to be the fastest in speed, they're competing to bring out the best driving tech possible. That's why it's very surprising to some that GM and Ford are both working on 10-speed transmissions, which will make a huge difference to modern luxury cars.
When Competition Meets CollaborationAlthough this news may be surprising to some, it's not the first time that these two companies have worked together. In fact, they collaborated on creating six-speed transmissions just in the last decades. Legally, this is a sound plan. Car companies can collaborate on designing new tech, but when it comes to the manufacturing process, they have to break apart and do this separately. This has led to many companies using the same engines in the past. For example, Mitsubishi, Chrysler and Hyundai all used similar engines in the last decade, after they worked together on designing them.
Why 10-Speed Transmissions?So, it's not unusual for companies to work together on new tech. However, many readers will be wondering why they're even bothering. After all, it sounds like they're focusing on something that doesn't really matter, in the grand scheme of things. What will this do for motorists? A highly tuned transmission can make all the difference to your driving experience. A transmission with more speeds can improve both mileage and performance when done correctly. It doesn't just rely on the speeds available though, the software controlling it needs to be done well too, in order to help you get the most from your car. A car with several speeds can be created with some overdrive gears, that are designed to improve fuel performance. These gears will keep the engine running especially slowly, even if the car is driving at speed, such as down the highway. The art of creating such engines for enhanced speed, without creating the annoying 'jerking' feeling that some engines get when you change gears. It's still to be decided whether GM and Ford can do this together, though.
Alternatives to Multi-Speed TransmissionsAlthough large advances are being made in creating multi-speed gearboxes, some companies are taking a different approach. For example, companies like Subaru, Honda and Nissan are going a different direction, creating CVTs. These are created with a belt-drive configuration that use variable diameter pulleys. These constantly adjust the ratio to create the correct setting for the driver. While these are great for some drivers, others don't enjoy the feeling of gearless driving. Because of this, some developers have programmed in modes that mimic the feel of driving multi-speed cars, or let the driver pick from several different modes. While there are a lot of benefits to CVTs, many drivers still prefer the way multi-speed gearboxes feel to drive.
History of Multi-Speed TransmissionsOf course, this partnership isn't the first time that a new style of multi-speed gearbox has been created. At time of writing, Chrysler Group are putting nine-speed gearboxes into the Dodge Dart, and the upcoming 2014 Jeep Cherokee. They're also a pioneer in using eight-speed gear boxes in their line ups, such as in the Ram pickups. Seven and eight-speeds are actually quite common right now with luxury car brands, so you may already be familiar with them. With 10-speed transmissions being worked on now, we can now expect to see some great leaps forward in how multi-speed gearboxes work.
The Financial Incentives of Co-CreationGM and Ford say that by developing their new engine together, they can help save the consumer a lot of cash. This is especially true of those who drive smaller cars. With a 10-speed gearbox, the driver will have more control over fuel consumption, meaning they're spending much less at the gas pumps. Of course, it's not just the driver who's saving money. By choosing the develop this new technology together, GM and Ford are saving themselves potentially millions of dollars in development cash. Of course, whether they pass the savings on to the customer remain to be seen. Either way, such collaborations offer many benefits to consumers. There's no word on when the new 10-speed will be made available to the public yet, as it's still in the planning stages. However, if more companies follow the lead seen here, we could see some new and exciting changes in motoring before long.
They say a car is the sum of its parts – if you take but one piece out, then a well-made racing machine just flat out won’t work. Racing rigs are built for performance and sheer efficiency – there’s nothing superfluous about a car made to go well over a hundred miles per hour. But some machinery deserves a little more credit for the demanding work a car goes through to attain such speeds, and maintain them. And while every layman focuses on the engine, it’s the transmission where the real magic happens. A transmission is more than a few gears and an input and output shaft. It’s a complex system of components built with the specificity of an orchestral piece made for the climax of a classic opera performance – ideally, transmissions are made to perform in certain environments and under specific conditions. A race car and a van will have differently built transmissions, and transmissions come as automatic, continuously variable, automated manual, dual-clutch, and more. That’s why it’s so important to have the right transmission for the job – and if you’re looking for a classic, no-fuss overdrive automatic transmission with four speeds, then a solid choice is to start with a stock 700R4 and go from there. The reason that’s such great news is because if you’re driving a Chevy (from your uncle’s old pickup to a hot 90s Camaro), chances are you’ve already got a 700R4 sitting pretty in your rig, and working with what you have – one of the finest pieces of GM workmanship in terms of sheer reliability as an AOD – is going to save you the small fortune you might’ve had to spend on a brand-new transmission. Trust us: you’re not cutting into your car’s potential with a 700R4. In the right hands, you’ve got yourself a serious racing transmission. But it’ll take some surgery to get it there.