Any one here changed out their diffs and transfer case fluids?

[Scott S.]

The front and rear differentials only hold something like
1.5 to 2 quarts gear oil, that's not much fluid for
a couple hundred thousand miles, yet MB does not
recommend a service. Any thoughts?
1999 ML 430 as per owner's manual; rear 80w-90
front 90w
transfer case Dexron III

[mickey.1430]

First we were told that regular oil was OK and that the tranny was filled for life. Nothing was said about diffs or transfer case. Now MB is in litigation about the oil story, and, I supect, will soon be in litigation over the tranny story. Personally, I switched to synthetic at the first change and do not burn oil. My tranny went out at 95k, oil smelled like a mens locker room and the fix cost about $6k: thank you MB for the extended warranty. Do I believe the rest of the fluids will last forever. Sure, but only on paper. And that is why I did a diff and transfer case change at about 110k. The cost is very small, probably something like $100-$125US, cheaper if you do it yourself. I have 124k miles on now, truck runs great, engine is just now getting broken in, averaging 21.5-22 mpg on trips and I hope to log many more miles before the model change. Your truck, do what feels right.

[Scott S.]

Sounds like you're getting great mileage with it. Too bad
about the tranny at only 95K tho. Yeah, ain't no way I'll
do those 10 to 13K oil changes and allow that tranny
to go unserviced. The diffs and transfer case are easy
to service. The only thing I have to research on the
transmission is the "adaptive driving electronics", the
MB tech on another forum is advising to have it "reset",
because it allows for wear and tear and fluid degradation
as you drive. I'll find out.
It's funny though, my MB dealer has a young girl as
a service manager, and I am not slamming her in any way
for any reason. I believe she is totally dedicated to MB.
But she told me absolutey do not change the engine oil
until the FSS instructs me to do so. Well my wife ate
this up hook line and sinker. The girl told us she knew
this is going to be totally different from any vehicle
we have ever owned, (Chevys, Ford, Dodge) and we will
have a tough time getting used to a 10 or 13 thousand
mile oil change but we have to believe in Mercedes.
I asked about transmission fluid change, she replyed
it cannot even be done as it is a sealed unit. MB
does not even want me to check the fluid level. Again
she told us to trust Mercedes. My wife bought into it.
And she is making the 500 dollar a month payment for
five years on a four year old vehicle. Back to the
female service manager, I admire her, If you could
only see her dedication to Mercedes.

[mickey.1430]

First of all, the tranny is sealed but not hermetically sealed. There is a clip on the tranny fluid dip stick tube which is broken upon removal: big deal. One has to purchase the dip stick to check the fluid level. It can and has been changed. Suggested numbers are in the 60k to 100k interval.
Two, the young'ens believe in the party line. That's OK because we have heritics who know better. For example, when inquiring about the recommended change interval for the tranny I was told that MB instructed the techs to change at 100k whereas a factory rep, yes a rep, suggested 60k for extended life, and some techs use 30k for themselves. I think 60k-75k is probably a save interval for piece of mind.
Three: As for 10k-13k oil change intervals, that is not a problem. The sump has twice the capacity of a traditional engine, so in terms of diluted junk, you are only doing 6k intervals which is only twice as long as the old 3k rule-of-thumb. With tighter manufacturing tolerances and great oil, that is no big deal. I know because I have my oil tested and they always tell me to run it longer.
Four: The odd thing is that the tranny has the same oil quality sensor as the engine but nobody seems to know what the readout numbers mean. The adaptive program uses the readout but in an unknown manner so I am not sure what resetting does after a change.
Five: tell the SA to keep speaking the part line but have her read some of the posts on this site, Mercedes shop and others.

[Scott S.]

Good advise. I have time to look into the trans service with 35,000 on the clock.
You mentioned the oil sump size. We've had the 430
for two days now and I keep forgetting it has an
eight and a half quart oil capacity. I'm too used to
those five quart changes.
My oil has been changed at MB at 10K , 20K and 30K,
and man is it black at 35K. With Valvoline 5w-40.
I plan on getting an oil analysis done.
A 6,000 dollar transmission rebuild/changeout would
sure bring a man down.
Did MB give a warranty with the tranny rebuild?
Thanks

[mickey.1430]

For my tranny, the fault codes suggested that the valve body was bad. This item is a hydraulic circuit responsible for shifting gears. The tranny pan was dropped, seal, valve body, tranny controller board, other small items, and ATF were replaced. There is a standard 12 month warranty on replaced parts. Of course, the replaced parts are also under the main warranty so the 12 month part is not that restrictive.

You may wish to look at posts by gillybenz on mercedesshop.com. He is a tech and has supplied some comments on tranny fluid changes. Also, check with your shop forman on the 'real' change interval. I have no doubt that under the tested conditions, the tranny fill will last a long time but in this country, we tend to have a much bigger operating envelope than in EU an encounter 'things that go bump in the night': ie. the fluid does not wear out but becomes contaminated and results in a jammed body (there are some 12 ball valves of which half are plastic and are easily jammed. Later MYs had protective covers installed to prevent fine grit from entering the body but it remains to be seen how well these work.). I don't know the failure rate for the trannies but I suspect it is not high unless it happens to you: then it is unacceptable.