Introduced in 2004, the Mercedes 722.9 7G Tronic transmission was one of the very first 7-speed automatic transmissions available in its day. It made use of a very complicated system of planetary gear sets and a Ravigneaux assembly that allowed for seven forward gears and reverse. The 722.9 valve body is responsible for allocating the right amount of hydraulic pressure to operate all of the various gears required to make this. Mercedes transmission work (including the 722.9 conductor plate, which can be quite complicated to repair. To learn more about it, click here). However, 722.9 valve body problems can still happen. In order to properly fix a 722.9 valve body, it will have to be modified beyond it’s stock form, to compensate for the design flaws that cause all of these problems. Companies like Street Smart Transmission do a good job of modifying the 722.9 valve body (they do things like modify the bores to improve fluid flow and eliminate premature solenoid failure), that way the whole transmission can function the way it was actually intended.
What Transmission Do I Have?
The Mercedes 722.9 7G Tronic transmission has seven forward gears and two reverse gears, which are made possible by two planetary gear sets and a Ravigneaux gearset that essentially combines multiple planetary gearsets into a single unit. Four multi-disc brakes and three multi-disc clutches are used to control the gears. Mercedes 7G Tronic conductor plate problems and 7G Tronic TCM problems prevent the computer from controlling these gears as it needs to, which can result in a number of symptoms. These include:
722.9 Valve Body Problems
No forward movement or harsh engagement due to K3 shift valve bore damage
Problem – One of the more common 722.9 valve body problems has to do with the K3 clutch, because it is applied in all gears (except 4th). Specifically, the problem lies with the K3 shift valve and bore, which can suffer from excessive wear and damage. This can lead to a number of 722.9 transmission problems, including:
- Unusually hard or abrupt gear changes
- Delayed gear engagement
- No forward gear engagement
- Harsh 4-5 shift or flare
- Premature K3 clutch failure
Solution – In order to prevent the hydraulic pressure loss that causes these symptoms, the K3 shift valve bore will have to be repaired (if it can’t be, the entire 722.9 valve body casting will have to be replaced), and a new valve installed.
Erratic transmission behavior due to supply pressure regulator valve bore damage
Problem – The supply pressure regulator valve is responsible for providing the shift solenoids with the hydraulic pressure that they need to operate. If there is excessive damage inside the bore, then the hydraulic pressure leakage will cause a number of transmission problems that include:
- Unusually hard gear changes
- Unusually soft gear changes
- Torque converter issues and damage
- Wrong gear starts
- Damaged clutches
- TCC and solenoid related DTC codes
Solution – This is one of the more common 722.9 valve body problems, and it can be solved by repairing the supply pressure regulator valve bore (or replacing the casting) and installing an upgraded valve to outlast the OE unit.
Harsh or flared shifts due to K1 regulator valve problems
Problem – The 722.9 valve body is known for excessive wear and damage to the K1 regulator valve and bore. Since the K1 clutch is applied from 3rd-5th gears, a number of shifts problems can occur, including:
- Harsh or flared 2-3 shifts
- Harsh or flared 5-6 shifts
Solution – To fix these issues, the K1 regulator valve bore inside of the 722.9 valve body will have to be repaired (or the casting replaced), and a more robust valve installed.
Overheating, failed clutches and poor shift performance due to working pressure regulator valve
Problem – Deep inside of the 722.9 valve body, the working pressure regulator valve is responsible for making sure that there is enough line pressure for the transmission to function properly. If the valve or bore or excessively worn or damaged, a number of serious transmission problems can occur, like:
- The transmission does not perform the way it should
- Inadequate internal lubrication
- Transmission overheating
- Premature clutch failure
Solution – This is one of the more serious 722.9 valve body problems, and if transmission overheating is suspected, the transmission should be carefully inspected for signs of heat related damage. Beyond that, the working pressure regulator valve bore will have to be repaired, or the valve body casting replaced. A more durable valve will have to be installed as well.
Solving 722.9 valve body problems
The problem with repairing a 722.9 valve body is that you don’t really know what kind of stress and extreme temperature changes they have been subjected to. This is why many people simply install a remanufactured 722.9 valve body, to eliminate the threat of the unknown. Companies like Street Smart Transmission use state of the art equipment to completely remanufacture the valve body. This is not like rebuilding, where new components are simply installed into the existing valve body. They use specialized equipment to analyze each valve body to see if it has been cracked or warped. A mechanic does not just simply eyeball it, a machine does the inspection, and even checks the tensile strength of the metal to make sure that it meets the original OE specification.
What Transmission Do I Have?
Once a casting has been selected for the build, all of the bores are modified, to make sure that the valves will function the way they were intended to. Then every single component from the check balls, to the valves, pistons and springs are tested and/or replaced. After that process is complete and quality inspected, they install all new solenoids (they also bench test them prior to installation), speed sensors and pressure switches. The finished product is then put on a Superflow AXILINE Valve Body Tester, which can simulate actual road conditions. This allows their ASE certified techs to verify the functionality, and make any adjustments or fixes before they ship it out to the customer. Street Smart Transmission also gives it a 1-Year/No Hassle Warranty, which makes getting a remanufactured 722.9 valve body almost a no-brainer. To learn more about the remanufactured 722.9 valve body and the remanufacturing process that Street Smart Transmission, give them a call at 1-866-812-7560
