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MB Paul
MB Paul, Mercedes Technician
Category: Mercedes
Satisfied Customers: 4317
Experience:  Mercedes Benz Qualified Diagnostic Technician
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I have an ML270 2005. Ongoing transmission problem. Over revs

Resolved Question:

I have an ML270 2005. Ongoing transmission problem. Over revs when changing 3 to 4 gear. I know the box leaks, I think the oil level is ok.
After a long drive towing a relatively light caravan to Cornwall, I lost drive on a couple of occasions. Got worse the last 30 miles of the trip.
In limp mode now. Worried about getting home next Sat.
I would welcome your advice.
Thank you.
Dave
Submitted: 3 years ago.
Category: Mercedes
Expert:  MB Paul replied 3 years ago.
Hi Dave,

In the first instance I would always recommend having the car checked on Mercedes STAR diagnostic tool to see what codes are stored in the transmission control unit.

If you are sure that the transmission oil level is correct (which a special workshop dipstick is required to confirm) then the next step will be to process the codes stored.

There are many possibilities but often the fault is down to faults with the sensors on the electrical plate inside the transmission or the transmission is slipping due to internal wear. The fact that you say the engine over revs when changing gear leads me to think that this is the most likely cause & often shows up more when towing.

If the transmission is slipping then there will be fault codes stored indicating that it has detected slip or implausible transmission ratios.

If it is slipping then you could try having the transmission flushed with an oil & filter change but in all reality it could very well need a replacement transmission or a rebuild of your unit. Obviously this is very costly.

In summary a definate check for correct oil level is recommended first, followed by a check for fault codes with a diagnostic tool & then processing these codes to determine the exact means of repair.

There are of course many other possibilities & I am advising you of the steps based on information you have given.

Best regards, Paul
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