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 .

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

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.

__________________
2016 Corvette Stingray 2LT
1969 280SE
2023 Ram 1500
2007 Tiara 3200

It's red.

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1973 280SE 4.5 (Sold)
1984 LWB 280GE (Sold)
2000 G500 NMLE - "Deep Throat"
2007 ML320 CDI (Sold)
2010 Porsche Cayenne S Transsyberia TipTronic (Sold)
2010 Audi Q7 3.0 TDI (Sold and Sorely Missed)
2014 ML350 BTC
2015 Audi Q7 3.0 TDI (On Order)

I went over to the dealer I am friendly with.. a mechanic drove it for a few miles and said it felt like a very minor slip.. he thinks the clutch packs may be worn but can't tell for sure unless hooking up to the computer and reading the adaptation values. He started to talk about rebuilding it when I interrupted and starting talking about a trans fluid change first.. he wasn't crazy about the idea.. said the car shouldn't need one. He wants me to bring it in for an hour labor ($100) for a diagnostic scan.. then who knows what he'll want to charge.

A local indy I know will change the fluid for me, but doesn't think it will help for $200.

I can do it myself.. but the only thing I am unsure about is the trans fluid temp, therefore I can't get an exact level.. but alot of people have done it here.

Then I could always leave things be and just replace it when it fails completely.. In the back of my mind I can't help but think I can make things worse by changing the fluid.

What should I do?

I went to the dealer at 78k to change the fluid and mb of palm beach mess it up. DONT EVER GO THERE. they also over filled it.

Hmm? These are two completly different trans.

The SDL's use the old 4 spd I forget the numbers. Change the fluid with regular ATF every 30k miles. I wouldn't bring one to the dealer they are a 30+ year old design any MB indi could do it.

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2016 Corvette Stingray 2LT
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