Mercedes-Benz Forum banner

722.6 Transmission Problem

25K views 17 replies 11 participants last post by  Luke81Roberts  
#1 ·
A bit of a background first. I have a 2007 E280 CDI 4MATIC (hence the 722.6 and not 722.9) with 200k km (124k miles) on the odometer. Soon after I bought it from its second owner, I noticed that the first few shifts when the car had sat in the cold were very rough. After some reading I reached the conclusion that it was the torque converter clutch solenoid which seems to be a common failure on these. I replaced it in January together with the filter, gasket, harness connector and 4L of oil (Fuchs Titan ATF 4134) and the problem disappeared.

The past few months I have experienced the following problem - when the car shifts from 1st to 2nd (or 2nd to 3rd if in 'C' mode), just before the actual shift, I can see the RPM drop from ~1800 to ~1600, there is a slight jolt/jerk and then the RPM get back to 1800-2000 and the car shifts to the next gear. This happens most often when I apply light and constant throttle, e.g. when I set off from a light and there is traffic. It feels like the torque converter slipping/engaging but not in the way it was designed to thus causing the jolt/jerk. This doesn't happen if I push the gas pedal hard. I've also experienced a few more violent jolts/jerks but maybe two or three times during my two years of ownership. I tried adding two bottles of Dr. Tranny Instant Shudder Fixx but there is no change. I also tried resetting the adaptations via Star to no avail. The fluid level is at the top range of the 80*C level when the car is at operating temperature.

The previous owner had replaced the transmission oil a few months before I purchased the car at around 180k km (112k miles). I asked the local MB dealership for all the invoices they have on my car for servicing (which was done there up until 100k km (62k miles)) and there is none on transmission fluid changes.

I am not completely sure I started experiencing this issue after the TCC solenoid replacement but even if it happened in the past, it was less noticeable. Do you think the previous owner might have noticed this and added some additive when he replaced the transmission oil to mask it so when I drained the oil and put new one in, the problem become apparent again?

At any rate, I need to figure out what to do now. I disabled the TCC solenoid using Star and the problem wasn't there so it is definitely the torque converter that is causing it. Could it be that the new solenoid I put in is faulty? I don't feel like spending 600-700 euro for a reconditioned TC if it's just a 50 euro solenoid that's defective. I find it hard to believe that the TC has gone at only 200k km.

The worst part is that had I decided to sell the car when the weather gets better but now it has this problem and I am not the type of person to try and sell a car with a major fault..

Any tips and ideas would be welcome.
 
#2 ·
I think you're on to something in the TC circuit not functioning properly. Solenoid is not likely the culprit. TC could be bad, however there are other factors to consider as well including the conductor plate. There are two valves on the valve body that control the TC. Slop in those valve tolerances can cause these problems. For an iterative approach you may want to try a complete flush or transmission fluid. Did you note the color of the old fluid when you added 4 liters? Next would be the conductor plate, then a valve body rebuild (where all valves are vacuum or pressure tested.) Rebuilt torque converter is last on the list. You may want to search Sonnax, Mercedes, 722.6 for more info. I went through this 5 years ago at 100k. I ended up doing all of the above. 722.6 is workhorse of a transmission. These are issues are not out of the ordinary.
 
#3 ·
The fluid was red and clear but it was fully drained and refilled by the previous owner a few months before he sold it to me. I did notice some black residue on the valve body though.

Someone else suggested I do the torque converter adaptations via STAR so I'll be trying this out with a friend over the weekend.

Thanks
 
#5 ·
I am pretty sure it's something TC-related as the problem disappears when I disable the lock-up solenoid. I made two videos:

- here you can see the rpm drop slightly from ~1500rpm and the car jolts slightly, in a few seconds the car upshifted

- the same happens here but around ~1600rpm, again the car jolted and a bit after the clutch was applied the gearbox upshifted..
 
#8 ·
Lots of tranny fluids are red, doesn’t mean its the correct fluid, no reason to put an additive in. And most places do not drop the pan or flush the TC and cooler if you dont do this half of the old fluid remains. Not only that they will give you bull about why its bad to change out all the fluid ... they are hoping you will be back with more problems because the tranny service was half-assed. And typically the shop wont let you watch their half-assed job. So do it yourself takes about 1.5 hours or less, but make sure you flush the TC and cooler. Use this Ravenol M6 series 236.10 spec, change out pilot bushing and filter too.
 
#10 ·
I did replace the oil (and TCC lockup solenoid) myself - I dropped the pan, replaced the filter, gasket, and pilot bushing. 236.14 spec fluid is the latest version fluid which the 722.6 takes and the one I used (Fuchs Titan ATF 4134) is 236.14.



Thanks. That sounds exactly like my issue. I'll see if I can find that Sonnax kit. Most mechanics tell it is the TC but one guy said it is more likely that it is the valve body which is responsible for applying the TC lockup and if the issue isn't fixed for a long time, then the TC needs to be replaced as well as it gets worn in the process.