Should I change my Transmission fluid
Out Of Control!!
Joined: Aug 2010
Posts: 12,516
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From: Charlotte NC area
2019 WS222 S450 4-Matic / 2007 W211 E350 4Matic (Sold) / 2008 X164 GL320 CDI
Mercedes said the 7 speed should never have its fluid changed...then they later changed their stance and now say you should change the fluid.
5 speed is the same. If your trans fluid is cooked or full of metal bits, it cannot work and your trans is slowly tearing itself apart from the friction.
My transmission was misbehaving a lot, and after changing fluid twice and carefully filling using Mercedes trans dipstick, it's now driving excellent again.
Be sure you order the special trans dipstick!! Otherwise you are guessing how much fluid to pour in, and this alone is dangerous to the transmissions health.
5 speed is the same. If your trans fluid is cooked or full of metal bits, it cannot work and your trans is slowly tearing itself apart from the friction.
My transmission was misbehaving a lot, and after changing fluid twice and carefully filling using Mercedes trans dipstick, it's now driving excellent again.
Be sure you order the special trans dipstick!! Otherwise you are guessing how much fluid to pour in, and this alone is dangerous to the transmissions health.
Audi said the same about their ZF 5 speeds from around 2000.
ZF NEVER said it was lifetime fluid. Go figger??
P.S. I thought it was the 5 speeds that MB said were "Lifetime", and the 7speeds got the one change at 39K to 42K.
Senior Member
Joined: Apr 2014
Posts: 299
Likes: 3
From: Colorado
'03 SL55 AMG | 2021 AMG GLE 63s Coupe
Anecdotal evidence is fascinating, but let's talk science for a while:
Automatic Transmission Fluid (ATF) and Crankcase Engine Oil (CEO) are very different.
CEO deteriorates due to several factors including heating,
which causes it to break down,
and exposure to combustion products which it absorbs.
Contamination is mitigated, but not eliminated, by filtering.
The http://en.wikipedia.org/wiki/Crankcase is not a tightly closed system as gases are taken in and expelled as regards blow-by and crankcase ventilation systems.
An Automatic Transmission is a tightly closed system, so the only contaminants to the ATF would be debris from friction of internal components.
If ATF contamination was an unavoidable major concern on the order of magnitude of engine oil contamination, there would be an ATF filtering system employing ATF filters analogous to engine oil filers.
The friction causes heat, but nothing anywhere near the temperatures caused by the combustion that CEO is exposed to.
After an "initial break-in" period, if a transmission is contaminating the ATF with debris, that transmission design has serious issues.
So what above warrants anything more than one initial ATF change?
Automatic Transmission Fluid (ATF) and Crankcase Engine Oil (CEO) are very different.
CEO deteriorates due to several factors including heating,
which causes it to break down,
and exposure to combustion products which it absorbs.
Contamination is mitigated, but not eliminated, by filtering.
The http://en.wikipedia.org/wiki/Crankcase is not a tightly closed system as gases are taken in and expelled as regards blow-by and crankcase ventilation systems.
An Automatic Transmission is a tightly closed system, so the only contaminants to the ATF would be debris from friction of internal components.
If ATF contamination was an unavoidable major concern on the order of magnitude of engine oil contamination, there would be an ATF filtering system employing ATF filters analogous to engine oil filers.
The friction causes heat, but nothing anywhere near the temperatures caused by the combustion that CEO is exposed to.
After an "initial break-in" period, if a transmission is contaminating the ATF with debris, that transmission design has serious issues.
So what above warrants anything more than one initial ATF change?
Last edited by Honcho; Sep 6, 2014 at 11:42 AM. Reason: tried to eliminate double "Crankcase" caused by the link
Out Of Control!!
Joined: Aug 2010
Posts: 12,516
Likes: 628
From: Charlotte NC area
2019 WS222 S450 4-Matic / 2007 W211 E350 4Matic (Sold) / 2008 X164 GL320 CDI
The composition of the ATF, including friction modifiers degrades over time with temp and use (shearing of the fluid).
Yes, friction material contamination is greatest in eth early phases of life, so whatever you a first change is warranted earlier then the on-going change interval.
I am using numbers from ZF as there design and technology is very similar to our MB transmissions.
They say 50K to 80K or 8 years as a maximum life for ATF.
Less if used in hard.
Yes, friction material contamination is greatest in eth early phases of life, so whatever you a first change is warranted earlier then the on-going change interval.
I am using numbers from ZF as there design and technology is very similar to our MB transmissions.
They say 50K to 80K or 8 years as a maximum life for ATF.
Less if used in hard.
Super Member
Joined: May 2009
Posts: 673
Likes: 27
From: Frederick
2000 ML320, 2005 E320 CDI
I know this is an old thread but I wanted to update. I now have 295K miles on the car and the issues popped back up again. Changing the filter, fluid and crush washer again. When it is changed, I imagine we will be back to smooth shifting. These transmissions are pretty well built.
