Mercedes 722.9 Gearboxes
Over the past few years, the team here at
Valve Bodies UK have been repairing
problems with Mercedes 722.9 (7G). These automatic gearboxes share similar
problems and these are commonly a 3-2 upshift on light throttle or a jolty
shift down from 3 rd to 2 nd gear. Typically, a replacement
(electronic or mechatronic) has triggered this or the vehicle has been bought
with the issues already in place.
There are a variety of shift control programmes run by Mercedes and these are both matched to a car and the chassis number, torque converter and valve body type.
Below is some information on the Mercedes 722.9 (7G), the common issues and how these can be resolved. For more, please feel free to call us today on 0151 639 9022. About the Problems
Most often the issues will start as a result of the incorrect software being used with the valve body. Sometimes a valve body can be changed, making it different from the chassis number and therefore creating problems. Alongside this, there could have been an incorrect fitting at the factory. If the electronic plates (TCU) are altered and the software has been changed, then it is common for harsher shifts between gears to happen.
Even though this may seem easy to understand, things aren't always that simple. There are other things that can cause clunky shifts between gears, including mixing the solenoids. A solenoid is a coil of wire which is used as an electromagnet and these cannot be mixed. In total there are 8 and these are split into 2 sets.
One of these 4 are interchangeable and the other 4 closed. Mixing these up can be easy to do. Although, when it comes to fixing this, it can take a lot of time and be difficult to resolve. You can often find that a main dealer won't address this issue and will instead suggest a completely new gearbox.
Another issue that can happen is to do with the torque converter. Even though the UK is home to some great torque converter builders, that doesn't mean that there aren't issues. Mercedes torque convertors can be susceptible to a small amount of change to the parameters of a rebuild. As reduction is common, it is crucial to ensure that your converter is working to the best levels. If it doesn't, then you may see premature failure, sharp shifts from an incorrect lock up curve, and a low fuel economy.
Additionally, the solenoids control this along with a variety of lockup valve sizes and springs. These depend on the valve body type and the TCU software controls this. From our experience, we know that Mercedes use a standard 5 lock up curves in addition to a number of unique lockup curves.
Knowing where to start when fixing these issues can be difficult. At Valve Bodies UK our first step will be to check the adaption data. We do this to make sure that there are no other internal issues prior to work commencing. The adaptions that we carry out, look similar to this:
Once this has been done, our team will have the details that they need to know what is wrong with your transmission. We can read several things from the TCU, including oil pressures, wear, as well as torque convertor information. As soon as we have looked into the data it will be clear whether your gearbox needs to be removed to allow us access to the valve body details and coding.
After this, we will be able to see if the
vehicle's valve body has been correctly programmed to the car specific coding.
There is a large database of details and, using tools from Mercedes, it will
soon be clear if there are any issues. If the data can then be cleared, the
torque converter curves and shift can then be looked into using a recalibration
At Valve Bodies UK we use pre-set curves to
help recalibrate the shift pressures in vehicles. Sometimes the wrong solenoids
have been put into the incorrect positions and this is why we start by saving
any original data. This means that we can always go back to the vehicle if we
need to. Even though the process can take a while, it is the best way to
resolve any issues you are facing. Whether this is by replacing parts or
recalibrating, it will save time and money.
Another huge advantage is that it stops
you from purchasing a new convertor, especially as slight parameter changes
can be recalibrated. Below are two separate curves, both of which are correct.
These show that shifts and convertor curves can be different in similar cars
with varying valve bodies:
We offer to rebuild and recode our own TCUs
to provide a complete and reliable service for you. If there is any bespoke
coding that appears, we will keep these and ensure that your new TCU has been
replaced with these. Even though our clients have never asked to replace their
new coding with the original, we'll make sure this is kept to help build our
Mercedes 722.9 (7G) database.
Alongside this, we also have access to
valve body variations and can purchase new convertors or valve bodies.
Contact Us Today
At Valve Body UK, all of the work we do is
in house and we ensure that a competitive price is always provided for our
customers. Our key aim is to bring the pleasure back into your Mercedes,
returning it to its pre-incident condition.
If you would like to find out more, please
do not hesitate to call our team today on
. You can also fill in our 0151 639 9022 and we will be back in touch as soon as possible. contact form