Mercedes-Benz W163 automatic transmission slips
ML 270 CDIML 400
Why does the automatic transmission slip on a W163?
The most common cause is too little or foamed fluid. Overheating, or a fault in the torque converter lockup valve or the speed sensor, can also cause slipping. Check the fluid level and read the fault codes with a suitable tool.
How does fluid temperature affect how the W163 transmission works?
When the transmission fluid gets hotter than 100 °C, the gears start dropping out one at a time. Above 110-115 degrees only first gear remains. Low fluid, for example from an oil cooler leak, raises the temperature, so the cooler is worth checking.
Is automatic transmission slipping on a W163 always a fault?
No. Slip in the torque converter is normal operation, and its lockup is never fully engaged. Clutch pack slip, however, is a fault: the transmission goes into limp mode immediately. If the slip is somewhere other than the converter, have a workshop find the cause.
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