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Please have your transmission pan A 222 270 05 12 checked for electrolytic corrosion at the filler plug. There is a new improved pan for $125 US that allegedly "eliminates" the problem.
In NA they say the service is due at 70k miles. My buddy who is a 30 year MB Master Tech here and all over the world, says 40k Miles. I'm glad we did.
Cause: Electrolytic corrosion exacerbated by moisture and road salt at the drain plug. According to MBUSA this could cause "catastrophic failure" of the transmission if the leak was not noticed, or the assembly just failed. The replacement transmission is $8k!
If you were going to purchase a certified preowned MB with this transmission of any mileage/age one might consider making sure the new "improved" pan is in place and the service is performed. If you have one now check it.
Don't they teach automotive engineers about electrolytic corrosion?
I don't know how to post pictures but I have several.
Check it at 35k miles or before 5 years. Electrolytic corrosion and road salt, I reckon. We wash the car and the undercarriage regularly. I'm not sure if there is cladding over it or not.
Why doesn't MB use a non-metallic washer or a disposable heavy-duty plastic bolt??
Both the pan and bolt are made of steel, hard to get electrolytic corrosion just from that. Washer is copper, but if it was also steel then it wouldn't crush and seal.
I'd wager that's more from a failure of the coating where the threaded insert is welded into the pan, and rust spreading under the paint around it.
I've not seen a bulletin or "updated pan" about this, but now i'm curious and will look. On the bright side, the pans are pretty cheap, and if this happens and you catch it before it breaks through, it's not a terrible fix, the pan has to come off for the service anyway.
Last edited by ItalianJoe1; Jul 5, 2017 at 08:04 PM.
Mercedes SLR McLaren 722 S Is Extremely Rare Example Modified by McLaren
Slideshow: A one-of-one U.S.-spec Mercedes-Benz SLR McLaren Roadster became even rarer after a factory-backed transformation at McLaren's headquarters.
