dorfer21

I'm having a bit of trouble with a new to me C300 with the 722.9 tranny. I bought it knowing that there was an issue with the trans. I've pulled the VB and cleaned it, and done a fluid/filter change with new blue ATF, and that helped a lot. The TCM is VGS3

The main issue is there is some flare when it shifts from 2nd to 3rd, and I'm trying to nail down if the issues is due to the valve body, conductor plate or the clutches themselves.
I have 2 codes stored:
P0894 - Transmission Component Slipping
P0733 - Gear 3 Incorrect Ratio

My google-fu has turned up something about the K1 solenoid possibly having a bad seal and that may cause this issue, but I wanted to have the hive mind assist as well.
I'll try to get a video of the issue and add it later.

What say you all?

TimC300

How was the condition of the old fluid? Did you drain the TC as well, or just drop the pan and fill? Did you follow the Mercedes procedure when determining the correct fluid level, ie checking the fluid temp via scan tool?

dorfer21

Fluid was dark, but didn't smell like it was burnt or too old, granted I'm going by my old experience with Dec/Mercon ATF. I drained both the pan and TC, and followed the warm fluid level check using a IR thermometer as I don't have a scan tool the interfaces with the TCM.

I didn't see any signs of metal chunks/ shavings on the magnets either.

Also, this is a used transmission, the original was replaced at 114K, with a trans that had 82K and the car now has 144K.

TimC300

Well, you say the filter/fluid change helped alot, and you list those codes as "stored".

I'm assuming you still have shifting issues though i dont really know what "flare" means.

Have you erased the codes and they have come back, they are current?

I'm focusing on the fluid since its the easiest and also the first step in my opinion with trans issues. I watched a youtube video where someone did a filter and fluid change in a C63 but did not follow the Mercedes procedures, they didnt even check the fluid temp if i remember correctly. They took it for a drive and it wouldnt shift right. They finally looked up the procedure and did the fluid over again and it solved the issue.

Did you put in the same amount of fluid that came out?

dorfer21

I put in more than i took out. It had several more codes stored before i did the fluid change. The fluid change was done per the proper procedure.

yes, ive cleared the old codes and theses are the two that keep recurring.

‘Flare’ when it comes to trans is where the trans changes the gear ( i can feel the shift to third) but then the rpm’s climb and then drop, they flare up for about 1-2 seconds and then stabilize.

it doesnt feel quite like the clutches are slipping in the traditional way, more like the vb isn’t allowing enough line pressure immediately to keep them locked.

JettaRed

iTrader: (1)

1. Spend the money and get a proper scan tool. The LAUNCH Creader Elite 2.0 BENZ is a popular one.
2. What was the known issue when you bought the car?
3. Need some history of the car. 114,000 miles is too early for the tranny to fail unless it was abused. Was the previous owner the original owner? Was it properly maintained? Before you, has the fluid in the replacement tranny been changed?
4. Run your VIN through www.lastvin.com and look for code A89. Confirm whether you have it and let us know.

dorfer21

It has code A89. The other codes stored were trans related as well;
P0729 - Gear 6 Incorrect Ratio
P0732 - Gear 2 Incorrect Ratio
P076F - Gear 7 Incorrect Ratio (Manufacturer Defined)

they all were resolved once i did the fluid change and cleaned the contacts on the TCM.

i have a OBlink adapter and code reader the does all the relevant code reading and resetting that you can do without a Star or Xentry. This is not my first rodeo with auto repair, just my first with a Mercedes Benz.
I have service records going back to 2019. The owner that I purchased it from knew there was a trans issue and i bought it knowing that as well. He knew that trans issues were out of his league.
he said that the trans went into limp mode after it warmed up, but i never experienced that issue.

The owner previous to him kept the vehicle in good shape according to the records, EIS/ELS repair, oil service at the dealer. Air bag recall, etc.

cvx5832

If I'm understanding the discussion so far, the codes are gone after you worked on it and the only thing left is a perceived symptom of shift flare? If that's true, wouldn't that have stored a code since flare is essentially slip, and I know ratios are constantly monitored for variances out of range.

So with all due respect my question is, any chance it's a butt dyno calibration error?

dorfer21

no, the codes in the op are still there. And i can see the flare in the tach and you can feel the car stop accelerating while the engine rpms increase. This is definitely not a case of butt dyno misdiagnoses.

JettaRed

iTrader: (1)

Do you know why the tranny was replaced at 114,000 miles? There are 7 critical years of no maintenance records? One thing any Mercedes dealer does is record the visit and work done on the car. That becomes a permanent record for the car.

Since the tranny was replaced with one likely from a salvage yard, I wonder if it was every calibrated to the "new" vehicle. If the replacement was done by an indy, then maybe the calibration using XENTRY was never performed. That could be the cause of the problems from the beginning.

Odd Piggy

2-3 upshift is performed by releasing brake B1 and setting clutch K1. K1 remains set for gears 4&5, and is released for gears 6&7. Flare (slipping) on the 2-3 upshift is likely the result of slow actuation of clutch K1 which is controlled by solenoid Y3/8y3. The prime suspect is the solenoid, but a badly worn clutch could be the issue. However, before replacing any components, I suggest resetting the transmission to remove any adaptations. Adaptations affect solenoid fill times. If after driving for about 100 miles, the flare is resolved, a bad adaptation was probably stored. If not, the solenoid (it's on the conductor plate) would be the easier and less costly repair. Replacing the entire conductor plate would cover a bad solenoid, bad sensors, and a bad TCU. The clutch would require a complete tear down.

dorfer21

I pulled the valve body, and it looks clean. Nothing in the passages or in the valves.




The business ends of the solenoids dont look very good. Not like what ive seen in pictures of replacements. They didn’t have any major metal particles on them or in the bores. They all ohmed out lower than ive seen. I think they supposed to be 5.5, but these are all at 4.8.




also, i am missing a check ball. I only have 13 steel and 2 phenolic when i should have 14 steel.

i think someone was in this valve body once already screwing around.

anyone know what size these checkballs are?

What would happen if I replaced all of the
solenoids?

TimC300

Im finding they are 5.8mm. Can measure yours with calipers.

dorfer21

I found the same info, but the ones I pulled out are measuring .215, which is roughly 5.5mm (5.46) so I'm thinking these are NOT the OE check *****.
Not sure if it really matters as long as they seal, but I will try to source some 5.8mm check *****.

Odd Piggy

A missing ball could be the entire problem. Here’s a diagram with functions from the internet if you don’t have one.

https://atsg.drcar.ch/index.php?call...df&urltype=pdf

I have never measured the resistance of the solenoids. If they are all 4.8 ohms, that would seem right, but other 722.9 threads here are saying 7-20 ohms. Since you’re already into the bottom end of the transmission, new solenoids wouldn’t hurt if you’re not happy with their appearance.

JettaRed

iTrader: (1)

@dorfer21 those solenoids definitely look dirty, if not corroded. Not sure what that material is. Is it metallic? (Use a magnetic pickup tool to try to clean them.). If a magnet doesn't collect that debris and you can't clean them with tranny fluid, I would suggest replacing them. However, others will chime in and say they are not replaceable because they are matched to the valve body from the factory. I do have a set of used ones that I never installed that were going to try to fix my 2004 SL500 722.9 transmission, but I ended up replacing the whole valve body and conductor plate with the dealer. This was a couple of years ago and I'm thinking the total was around $1700, but certainly less than $2000 at the time.

Here are the ones I still have if you are interested. Send me a DM if interested.

dorfer21

I got the replacement checkballs. I could not find enough in 5.8, so i went with 5.5.

Now, researching the locations im seeing a few different layouts for the check valves. I see one that matches my 5 small and one larger valve. But that also has 3 valves in the upper body that i do not have. I also dont see any space for them though like on the lower body.

Is this expected for some of these valve bodies?

Odd Piggy

I suppose 5.5mm will work as long as they seat well enough to seal.
I’ve been inside exactly 4 transmissions and that’s been to put them back together exactly the way I found them, not to fix what someone else messed up.
But I do know this: The 722.9xx transmissions come in older NAG2 and newer NAG2+. Both of those have 400 & 700 variants depending on the engine and vehicle.
So maybe 4 different valve body configurations? Maybe more if the 4matic and AMG versions are different.
There should be an ID plate on the left side of your transmission with the number on it that shows exactly which variant you have (722 9xx *** ***). It’s also available on the data card. The xx is what is needed to find the exact configuration for detailed repair instructions. A copy of the WIS may help.

dorfer21

Thanks to everyone here for helping.

this is one of the best forums ive been a member of. And you have all been very helpful.

dorfer21

Welp…
the issue persists…
Next steps
1) visit an indy to have the trans adaptations cleared.
2) ‘new’ valve body.
3) trans rebuild.

thoughts on the next steps?

Odd Piggy

I assume that you still have both the 2-3 upshift flair and the codes.
Does your scanner support 2-way communication with all the modules or just the DTC memory? If it supports 2-way to the TCU, you may be able to clear the adaptations with it. At the least, do that or get it done before spending more.

You can do an on car reset, but I have heard that isn’t as good.

You have seen the valve body. If it and the valves don’t appear visibly damaged, it’s probably not the problem.

The clutch could be very worn or the actuator is failing. Once you are at that point, it would seem that a rebuild is the next step. A problem with this is finding a shop that will work on a Mercedes transmission if you’re not near a big city. Some of the chain locations will not work on MB trans. An option could be either getting a rebuilt or even a used transmission that comes with a warranty.

dorfer21

So far the codes have not returned, just the issue with the 2-3 upshift.

My scanner only does the DTC’s for MB. Is there a decently priced once that will communicate with the TCM? Someone posted a LAUNCH reader, but that doesn’t seem to do the TCM (unless i missed something)

unfortunately the main Transmission shop around here wont rebuild it. Im not that close to a major area to have it done and cost may be a factor. Im not opposed to just doing it myself, its not my only vehicle so if its down for a bit, im just out the extra gas my power wagon uses

JettaRed

iTrader: (1)

https://europeantransmissions.com/72...7g-tronic.html

https://fdt-online.com/722-9.html

Odd Piggy

That depends on what you mean by reasonable. It may be less expensive to just get an indie shop to do it. Many of the members recommend the iCarsoft MB V3.0. I can’t vouch for its capabilities, but it advertises transmission adaptations management. If you go with a mid range scanner from someone like Autel, expect to spend $600+.

dorfer21

Here’s a video

edit, its having issues with my file.