I used my mity vac to pull some fluid out just to check on the color.. it looks like mud. Smells a little funky, but not terribly burnt. I am getting a funny 2-3 upshift when the car is warm.. all other gears are perfect up and down. Do I dare change the fluid and filter or is it a death sentence? Car has 230k.. trans supposedly last serviced at 160k, although I have no documentation.

I would change fluid, torque converter too, and then add Trans-X available from any auto parts store.

transmissions are funny . I've rebuilt my share for my race car , and have learned that the cooler you keep it , the longer it lasts .

Why the factory runs the trans fluid through the radiator where it sees 220 degrees , without a external cooler in the return line .... is beyond me . Utterly stupid .

You only see this setup on a pickup truck with the " tow package "

If you can keep a transmission at 100 - 150 degrees , it will live for a very long time . At 200 degrees , the rubber seals start to harden and get brittle . After 80,000 miles of this , it starts to go downhill slowly . How it even lasts 80,000 is pretty good . Its like slow cooking a roast .

Now the funny part ..... not so funny though ..... once the fluid is burnt and black * sign of being wayyyyyy to hot * and starts shifting weird , then you change the fluid , that new fluid washes out the grime and gunk from the o-rings that are hard a brittle , and they dont seal at all now . Now your trans gets even worse because nothing is sealing , and pressure is lost .

So .... If I were you , I would start saving for a rebuild , and add a cooler After the radiator AFTER you rebuild it . Find which is the return line to the trans , and put a parallel cooler inline there . This will reduce temps tremendously .

Or .... cross your fingers and change the fluid .... sometimes you get lucky and its just starving for fluid because the filter is partially clogged .

Then add a cooler without hesitation .

I concur with BusyBenz on all except the Trans X. I would never use an additive of any kind unless it was an absolute last resort.

Len
'99 E300TD 75,000 miles

On a 722.6 you should only ever put MB fluid and a MB filter in their. Do not put anything else in their.

Besides the dealer charges just under $200 for a fluid change, just have them do it. They have the special tool that will measure the fluid temp so they can get the level right. Some things are just not worth doing yourself, what are you saving $100 by doing it yourself? To risk a $3k trans?

My friend had his done for the first time at 152k and it shifted a bit better. I would just change the fluid.

Also I am not 100% but I am pretty sure the original color of this fluid is not red, I think it may be a clean motor oil color. But I am not 100% sure.

__________________
1999 SL500
1969 280SE
2023 Ram 1500
2007 Tiara 3200

I hesitated on excepting this stuff too, but a lot of guys over in diesel discussion have used it as a last resort and they claimed that it freed up sticky valves etc and their tranny's worked better as a result. I have tried it too, but I still get flaring 3ed into 4th. Yes, I have tried adjusting it out via modulator valve but no luck! Oh, I've got 247K on it and I read that 250K is about all you can expect.

I like the cooler idea, I think I'll try that. Where can one buy an auto-tranny cooler?

alot of auto parts stores have them right there . With like the electric fans and radiator stuff .

Dont buy the outdated tube and fin kind thats made of 3/8 tubing bent in a S shape ........ get a parallel one ......Looks like a miniature radiator with flat wide tubes .

Heat kills transmissions . Well , kills about anything really .

I own two MB's and love them. Also owned tranny shop for many years.

If the fluid smells burnt (burnt "toast") and looks that bad, sorry its ready for a rebuild.

We would had refused to change the tranny fluid as it would further the problem and strip the clutches as new fluid is very "detergent"

Also sorry to say Mercedes makes a poor tranny (ZF's) and they just don't hold up as others.

John1

The 220F water enters at the top. The trans fluid enters the bottom of the radiator, where the radiator fluid has been cooled by air passing through the coils. It would be interesting to measure the RETURN coolant temperature; it may be 150F or so...

I'm partial to the change the fluid & filter first, then see. I don't see adding a cooler.

I had to replace my trans on the suburban at 80k. My SDL has 256k on the original trans. I can't believe that the MB trans is that bad...

Just another $0.02

Best Regards,
Jim

The fluid did not smell overly burnt.. just smelled like it needed a change. Also, like Hattie said, this fluid is NOT originally red in color. I have no experience with a 722.6 trans so I don't know if this color means it's time for a change, time for a rebuild or it's OK. Like I said I am getting a slight 2-300rpm slip on the 2-3 upshift.

If your transmission shudders a little and or hesitates between shifting from 3rd to 4th then it is probably your B valve(parts are 100 dollars)and depending on the MB model often can be done without removing the transmission......Many people listen to transmission shop owners that do not know much about Mercedes transmsissions except they will tell you it needs to be rebuilt...You would be wise to change your fluid and also drain the torque converter(very simple), change the filter, install a new gasket and refill with mobil 1 tranmission fluid(5 dollars a quart).....I have also used transX and it does work....I have added it to mobil1 ATF....I have never seen many american transmission last 2-300K miles...And I have had a number of MB's that have 200-300K and the transmission is still working...The return temp of the trans fluid is about 150-160 degrees depending on the model....I have never wondered about the trans cooler as much as I have wondered about the oil cooler...Jim

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James A. Harris

The fluids get greyish black in these because the wear part inside are made from graphite and discolor the fluid. If it does not smell burnt then the chances are it is fine, but changing it will not hurt from what I have heard. Use only the MB SYNTHETIC fluid, use a new filter, drain the TC from the plug and you should be good to go. Since the material and special tool to read the level will cost about $125 to do it yourself you might just let a good indy shop or dealership do it, even if it lands up being $200 or more. They know how not to overtighten the bolts and where to check for leaks (at the electrical interface plug) when they are working on it. Just my $.02.

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Marty D.

2013 C300 4Matic
1984 BMW 733i
2013 Lincoln MKz

I copied and pasted the following post by Gilly on fluid and 722.6 transmissions:


"OK, here it is verbatimcomments in parenthesis are mine)

--------------------------------------------------------------------------------

Filled for life?
The 722.6 Automatic Transmission uses a special oil and is said to be filled for life. The oil can only be purchased through the Mercedes-Benz dealer using part number 001-989-21-03-10 (I think they mean 589, not 989 DG) A 722.6 holds about 9.3 liters and the fluid is sold by the liter. Checking the fluid is accomplished by breaking off the red locking seal located at the dip stick. the lock is replaced after the oil is checked. Use part number 140-991-00-55 for a new lock. There is no dip stick to check the ATF. You need a special tool to check the fluid on all 722.6 transmissions, part number 140-589-15-21-00. The oil level is a critical factor in transmission shifting. See Service Information 27A95105 for details. When you refill, or check thetransmission fluid level make sure that you check the level with the special tool and at the correct temperature. The latest information from Germany is that we should fill the oil to the MAX line. Not overfilled, just maxed out. This is said to improve shift quality. At normal level it is possible for the oil to form air bubbles. The increased level helps to minimize this. You might want to remember to try this on customer complaints involving shift quality before you replace any component. Along with setting the adaptation you would be surprised to see how much of an improvement you will see.

The Automatic Transmission fluid is said to be filled for life. We never specified who's life. (Yes, they actually wrote that in this!-DG) The transmission control module contains a program that keeps a running count of the "calculated" cndition of the ATF oil. (Note from Gilly-I believe this was deleted from the modules right around 2001-2002, not there anymore-DG) The factors that affect the oil are time and temperature. The counter is incremented with engine running time and incremented greater with higher ATF temperatures. The Hand-Held Tester (now SDS-DG) displays a numerical value that represents the value of the calculation. At some given point in time Germany will tell us (still waiting, evidently-DG) which number means its time to change the oil. For now there is no service interval for the ATF oil. If you replace a transmission you should re-set the counter back to zero to account for the new oil. If you are doing internal work and you are replacing the oil you should also re-set the counter. It is acceptable to drain the oil out into a clean container and reuse it, provided it was collected using the MB filter funnel. Remember to flush the converter and kines before installing the new transmission. You should also replace the converter if the transmission was HEAVILY contaminated with metal. Make sure you return the converter with the transmission to warranty. Fine metal particles in the bottom of the pan are allowed. (I think what they mean here is that fine metal particles are considered an "acceptable" condition, do NOT replace transmission, as you will see if you read on:-DG)

The Color of Money:

We have been conditioned to judge the quality of the transmission fluid based solely on it's color and smell. We have no way of judging the frictional quality. The rules have changed. (didn't Iaccoca say that too?-DG) The bright red color that we are all used to seeing may not be what you see when you look at the ATF in a 722.6. The reasons that the oil looks differently are as follows:

1) The oil may appear dark red due to the graphite material that the friction discs contain. This does not change the characteristics of the oil. Do not change the oil or transmission if the oil appears dark red or even if it has a yellowish tint to it. The color will change with time and temperature. As of 10/97, the manufacturer of the oil has agreed to put more red particles in the oil.

2) If a copper color is seen in the oil pan the bushings of the front or rear planetary gear set may be in the process of wearing out. Inspect the bushings and if they are defective replace the complete transmission. If they are not defective, then the transmission is repairable.

3) If a silver color is present in the oil it may be a clutch and steels moving up and down on the hub as they are being applied. This is normal! Use your best judgement here. If the particles are fine they should not cause problems as they will be trapped in the filter. The fluid could be drained, including the torque converter, and the lines flushed and the valve body should be disassembled and cleaned, replace the filter of course. This usually takes care of the problem. If you take the time to inspect and clean each slide valve for ease of movement and base position you will have a better valve body than a new one from spare parts. In more severe cases where the particles are large, then something is in the process of self destruction and the transmission should be either replaced or repaired. Don't forget to check the electrical solenoid valves. Shine a light through the top of it and see if it "leaks". If you drop the transmission oil pan (I think they mean "remove the pan"-DG) and you find yourself feeling like a miner panning for silver, or knee deep in a graphite colored mud, then it's time for a new transmission. You may have noticed that the new pans are painted black on the inside. The metal particles show up better against a black background as opposed to the previous unpainted silver pan. You must get used to seeing some metal in the bottom of the the pan, with this transmission this is normal.

4) Smell the oil. You know by now what burnt oil smells like. If it looks burnt, and it smells burnt, then its burnt.

Example: Try looking at the adaptation values for K3. If the numbers are high, then you have a K3 problem. If the customer is complaining about shift quality going in and out of third gear, repair K3.

5) Make sure you understand the complaint before you disassemble the transmission. Use the HHT (SDS now-DG) adaptation screen values along with the shift application chart to see which shift members are applied during your customer complaint so you will know where to concentrate your efforts when you disassemble. Remember to disassemble the transmission like a surgeon, you need to observe the condition of seals, rings, c-clips and shims as well as being aware of the potential for missing parts.

Repair or Replace:

Use the transmission oil pan as an indicator when deciding to repair or replace the 722.6 transmission.

The following pictures (sorry folks, I'm transcribing the written part only, no pictures-DG) are for reference as to which transmissions should be replaced and which should be repaired.

(picture shows a black pan with some small "dots" here and there-DG) This is a normal oil pan for a 722.6. The fine particles are normal. Do not replace this transmission.

(can't tell what's "wrong" with this picture-DG) The brass colored particles may be a sign of a bushing problem. This transmission may be repaired.

(can't tell by the next picture either what the problem is supposed to be, rotten copies!-DG) The metallic sludge indicates that there is a major mechanical problem. This transmission would probably cost more to repair than to replace.

(This picture you can see obvious copious amounts of metal shavings, a pretty good coating of it-DG) This picture also indicates internal damage has been done. This transmission would be replaced (as well as the TC and flushing lines and cooler, etc-DG)."

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Paul S.

2001 E430, Bourdeaux Red, Oyster interior.
79,200 miles.

1973 280SE 4.5, 170,000 miles. 568 Signal Red, Black MB Tex. "The Red Baron".

After a quick search, I found the thread that contained the above post.

1999 S500 with 722.6 Automatic Transmission Filled for life?

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Paul S.

2001 E430, Bourdeaux Red, Oyster interior.
79,200 miles.

1973 280SE 4.5, 170,000 miles. 568 Signal Red, Black MB Tex. "The Red Baron".

Thanks for the info. That article makes mention of "K3".. what is this and how is it repaired? I do have shift quality issues going into 3rd.