Upgrading a 4L70E Transmission
The 4L70E is one of several GM-produced electronic automatic transmissions developed as a successor to the Turbo-Hydramatic line of transmissions, some of which continue to be excellent transmissions for plenty of performance builds looking for a good stock transmission with a TV cable over electronics.
Alongside the 4L60E on one spectrum, and the 4L80E on the other, the 4L70E sits between two ends of spectrum of transmission needs.
Depending on what you want, it may be an excellent transmission and just the thing you’re looking for. It’s all a question of specialization. Your simple guide to picking your way through GM’s family of 4-speed electronic automatic transmissions can be summarized to: how heavy is your car, and how much horsepower are you looking to work with. Heavier builds steer towards the larger, more imposing, power-hungry and powerful 4L80E, and the smaller your car is, the more you should be skewing towards the 4L60E.
But life isn’t always simple, and in this case, there’s more to it than just that. Here’s a quick little rundown on the 4L70E, its relative history in the world of GM transmissions, and its potential – potential that transmission experts can take, unlock, and transform into pure performance.
History of the 4L70E
GM’s transmissions play a big part in the history of American automobile manufacturing, and alongside Ford (a “friendly” competition that survives to this day), the automatic transmissions of the late 70s and early 80s pioneered the inclusion of accessible overdrive – a new gear made more accessible to transmissions after that point, designed to allow a car to maintain speed while cutting down on RPM and fuel usage, for a much better fuel economy.
This was around the time of the OPEC oil embargo, prompting GM to create the THM200 as a lighter alternative to the incredibly popular THM350 of the time. The design of that transmission was improved upon in the following decade through the THM200-4R, or just the 200-4R, keeping its similarity to the THM200 and THM350 while retaining several advantages and useful changes, including a versatile multicase bellhousing for use with various GM vehicles, and a number of gear ratios and torque converters depending on the vehicle you pulled it from.
Following the success of the 200-4R, the next-in-line kept the new designation, and the 700R4 transmission was born in 1982. This is the first of our new automatic transmissions, as the 700R4 eventually was renamed into the 4L60, in keeping with a new GM naming scheme, in 1990. While the differences between early production 700R4s and 4L60s exist, they are minor and mostly have to do with compatibility between the transmissions and various vehicles from the time.
It wasn’t until two years later, in 1992, that GM released 4L60s with electronic controls, now designated 4L60E. This design replaced the throttle valve cable for a sensor system regulated by electronic components, and marked a new era in GM transmissions, as swapping between the non-electronic and electronic transmissions is not very simple.
Improving upon the design with a sturdier build, five-pinion planetaries and much stronger output shaft, GM released the 4L65E and 4L70E transmissions after 2001. Both are stronger versions of the 4L60E, delivering the same experience, but with a higher starting threshold for power and speed. The only difference is the speed sensor located in the pump of the 4L70E, and the convenience you personally have in picking between one and the other depending on your available resources, market prices, and any existing deals.
4L70E Transmission Stats
The 4L70E as its name implies is a 4-speed longitudinal automatic overdrive transmission by GM. The E in its designation indicates that it uses electronic controls over a throttle valve cable, and it sets itself apart from the previous 4L60E by providing a sturdier build, including both five-pinion planetaries over the 4L60E’s four-pinion planetaries, and an improved output shaft. Its outer case material is aluminum, and it clocks in at about 133 lbs. dry, without any transmission fluid.
Although it is improved, it shares the same stock case design with the 4L60E, and its close cousin the 4L65E. All 4L__Es utilize a torque converter lock, and the 4L70E is no exception.
The gear ratios for the 4L70E are:
1st gear: 3.06
2nd gear: 1.62
3rd gear: 1.00
4th gear: 0.70
The 4L70E sports an entirely different valve body from the 4L60E to accommodate the change in solenoids, and the internal wiring is completely different. Care needs to be taken when deciding how to install a 4L70E in cars that originally used an older GM transmission – while it often bolts just in, the car may not be compatible with the electronic components in the 4L70E if it’s a model before 1996. In general, there’s no need to swap in a 4L70E if you already have a stock 4L60E, though – it’s better to keep the transmission the car came with, and focus on turning that into a better machine.
4L70E vs. 4L60E vs. 4L80E
The differences are almost impossible to tell at first glance, but a quick look into the transmissions themselves give you an idea of how they differ. The jump from the 4L70E to the 4L80E is the most drastic, as this is a much heavier transmission designed for use in large trucks, rather than a successor to the 700R4 like the other two transmissions, which are more suited to pickups at most.
The 4L80E weighs 178 lbs. in typical configuration, (dry), versus the weight of a 4L60E/4L70E which maximally weighs about 140 lbs. Your best bet towards visually distinguishing between the 4L60E and the 4L70E is checking the service parts identification sticker if it’s the stock transmission in a GM vehicle. Look for M70, which denotes the 4L70E. Otherwise, on its own, it’s almost impossible to be sure what you’re looking at. They all use the same oil pans and the designations are interchangeable depending on the year and build of the transmission.
Between the 4L60E and the 4L70E, the biggest difference is time. The 4L70E is a straight upgrade to the 4L60E, appearing on the market several years after the 4L60E has had time to shine. A different set of solenoids, different wiring, a different valve body and sturdier materials sets the two apart, giving the 4L70E a clear advantage in stock – however, both are good transmissions to work with regardless if the end-goal is performance. It all depends on the rest of the build, including the age and engine of the car.