History of ZF4HP22 and ZF4HP24 Transmissions
ZF, short for Zahnradfabrik Friedrichshafen, has been making automotive parts for over 100 years. They’ve been making automatic transmissions since the 1960s, and are known today for creating some of the best automatic transmissions in the world.
The ZF4HP22 which was released in 1980 was a huge success from the start, and continued to be released in new vehicles until the early 2000’s. It was mostly built for sedan cars like BMWs, Jaguars and Audis, but also came in SUVs like the Land Rover, and sports cars like the Porsche 911.
While the 4HP22 and 4HP24 are still running in many vehicles to this day, they were the last 4-speed automatic transmissions made by ZF. They eventually got phased out to make way for 5 speed transmissions like the ZF5HP24.
A ZF4HP22 Transmission
Specifications of the ZF4HP22/4HP24 Transmissions
Both the ZF4HP22 and ZFHP24 transmissions have 4 forward gears and lock-up torque converter clutches. They are both considered to be medium-rated transmissions, the 4HP22 can handle up to 400 Nm of torque, while the 4HP24 is rated to handle up to 450 Nm. With the right upgrades to the internals and clutch packs, the transmissions can handle even more torque and horsepower.
The 4HP22 came in two major models. The first early model was a hydraulically operated transmission, and the second model released in 1986 was electronically controlled by the use of solenoids.
While there are hydraulic and electronic versions of the 4HP22 transmission, the 4HP24 only came in an electronic version. Internally the parts are almost the same, but the ZF4HP24 has a different torque converter, which is stronger and designed for bigger and more powerful engines such as the 4.6L V8 Land Rover Discovery engine. The bellhousing is larger on the 4HP24 due to the larger torque converter.
There are three different types of torque converters that can be used with the 4HP24 transmission. An owner would pick the torque converter based on the application and bellhousing pattern.
Gear Ratios of the 4HP22/4HP24 Transmissions
Strengths of the 4HP22/4HP24 Transmissions
Since its release, the 4HP22 and 4HP24 have been proven to be highly reliable and dependable. They are extensively used today in a wide range of vehicles such as Land Rovers which are known for their ability to handle rough terrain.
Both the 4HP22 and 4HP24 have lockup torque converter clutches (TCCs). This helps improve performance and driving experience in a number of ways. When driving at cruising speeds, usually above 3 rd or 4th gear, locking up the TCC provides a direct drive from the engine to the drivetrain. This means that there won’t be any slippage and energy wasted in the torque converter, immediately leading to improvements in fuel consumption. Less slippage in the torque converter significantly reduces the heat generated and allows the vehicle to attain a higher top speed.
While not all the 4HP22s are electronically controlled, the electronically controlled version of the 4HP22 and the 4HP24 provides distinct advantages over the hydraulic version, because of their high degree of controllability, allowing shifts to be timed based on various engine parameters and inputs. When tuned properly, the transmission is known to have smooth shifting. It’s also usually far easier to diagnose any fault using an electronically controlled transmission.
Weaknesses of the 4HP22/4HP24 Transmissions
When the 4HP22/4HP24 transmissions do have problems it’s almost very likely to be caused by overheating due to towing trailers, power upgrades or poor cooling capacity.
If required, owners can either upgrade their cooler or add another cooler. They can also look at possibly keeping the TCC locked longer to avoid excess heat generated from slippage. Instead of locking the TCC in 4 th gear, the TCC can be set-up to lock in 3 rd or even 2nd gear.
The C1/C2 one-way clutch on the 4HP22 is a known weak point and so is the planetary gearset. The 4HP22’s internals will need to be upgraded especially when you intend to use it with a more powerful engine. This upgrade can be done using the internals of the 4HP24.
Custom vehicles that use the 4HP22/4HP24 Transmissions
The transmission is found on a huge variety of vehicles, however when it comes to custom builds, you will find them mostly behind customized Land Rovers. 9 out of 10 times they are used to convert a manual transmission Land Rover Discovery to an automatic. There weren’t so many Land Rover Discoveries available with automatic transmissions, so the transmissions are extensively used on 85-2004 Discovery conversions.
For Land Rover Defenders built after 2007, engine swaps are a commonly realized upgrade. In order to use an engine of a different make, you will need to use a transmission controller like the COMPUSHIFT in order to get the transmission to work with the new engine.
A First-Generation Land Rover 4HP22
A Land Rover Range Rover P38 which featured the 4HP22
ZD4HP22 and ZF4HP24 Transmission Control using the COMPUSHIFT Sport
Whether you’re planning on doing a manual to automatic conversion, engine swap or are just looking for better ZF4HP22 or ZF4HP24 transmission control the COMPUSHIFT Sport can make your project a success.
The COMPUSHIFT Sport can be used with any of the electronically controlled versions of the 4HP22 and all the 4HP24 transmissions. Using the COMPUSHIFT Sport gives you the chance to modify the TCC lock-up and transmission’s shift strategy.
These transmissions use an output speed sensor (OSS) and throttle position sensor (TPS) to control TCC lockup, however with certain engines that have manifold absolute pressure (MAP) sensors, you can use the data from those sensors to modify shift pressure appropriately based on engine load. This helps avoid rough shifting, which commonly happens during a downshift when you’re slowing down and suddenly add more throttle. With a turbo-diesel engine this downshift can very jerky, because you might have a second of turbo lag followed by a clunky downshift when accelerating.
The COMPUSHIFT can be wired to the MAP sensor in a diesel engine and a vacuum sensor in a petrol engine. For this modification to work properly, you’ll need to install a pressure sensor kit to sense the transmission line pressure.
Finally, while owners can use the factory gear position selector, many other aftermarket potentiometer-based switches and tip-tronic paddle shifters can be used with the COMPUSHIFT Sport.
The COMPUSHIFT Sport comes with stable pre-loaded settings to control the 4HP22 and 4HP24 transmission. They can be easily modified with the accompanying mobile app over a wireless Bluetooth connection. The mobile app allows you to monitor all aspects of the transmission’s operation on the go, allowing you to make changes as you see fit.
To get the ZF4HP22/ZF4HP24 transmissions to work with your vehicle, you will have to get the right kit and sensors according to your vehicle’s specifications. To find out what you need for your build, head on over to our Configurator Tool to create your custom kit today.
To get details on the COMPUSHIFT ZF4HP22 or ZF4HP24 transmission controller click the below link: