Experiencing difficulty shifting gears in your Mercedes W201, especially at higher engine speeds? This is a common concern for owners of these classic vehicles, and understanding the potential causes can help in diagnosing and resolving the issue. This article delves into a specific problem encountered with a W201’s manual transmission, focusing on symptoms that point towards clutch drag at higher RPMs.
The initial investigation started with checking the basics. The selector linkage bushes were inspected and confirmed to be in good condition, ensuring smooth mechanical operation of the gear selector. Gearbox fluid level was also verified and found to be adequate. However, a minor transmission fluid leak was detected from the bell housing area, suggesting a possible issue with the gearbox input shaft seal. This is separate from a previous hydraulic fluid leak from the clutch slave cylinder, which had been addressed with a replacement.
Further testing under driving conditions revealed a crucial detail: the gear shifting difficulty is significantly worse at higher engine speeds. While gear selection is smooth and normal when the engine is idling, the problem intensifies as RPMs increase. This issue isn’t limited to just first and second gear; it affects all gears, becoming more pronounced in lower gears due to the higher engine speeds typically used during acceleration. When attempting to shift gears at engine speeds between 4000 to 5000 RPM, clutch release becomes nearly impossible. Interestingly, engine braking remains functional even with the clutch pedal fully depressed at these higher RPMs, indicating a failure of the clutch to fully disengage.
To further isolate the problem, a test was performed in neutral. Revving the engine above 2000 to 3000 RPM made it impossible to engage any gear until the engine speed dropped back to idle. This observation strongly suggests that the clutch is not releasing properly when the engine is spinning faster. The clutch seems to be exhibiting characteristics similar to a centrifugal clutch, remaining partially engaged at higher speeds.
While the clutch pedal feel remains normal, and there’s no grinding when selecting reverse at idle (which would indicate clutch drag under normal circumstances), the symptoms clearly point towards a speed-sensitive clutch release issue. The fact that the problem is absent at idle but progressively worsens with engine speed is a key diagnostic factor.
Adding another layer to the complexity, the vehicle previously suffered from clutch shudder, particularly when cold or in humid conditions. This shuddering issue had lessened after the slave cylinder replacement, possibly due to reduced hydraulic fluid contamination in the bell housing. However, with the sudden onset of the gear shifting problem, the clutch shudder has completely disappeared. This simultaneous appearance of one problem and disappearance of another, coupled with the engine speed sensitivity, strongly suggests a mechanical clutch issue rather than a purely hydraulic one.
It’s also worth noting that this 1990 model W201 is equipped with the later gearbox and clutch system, featuring a dual mass flywheel. This component, while offering improved refinement, can also be a source of clutch-related problems.
Moving forward, re-bleeding the clutch hydraulics is a logical next step to rule out any remaining hydraulic issues, although the speed-dependent nature of the problem makes a hydraulic fault less likely. The focus is now shifting towards investigating potential mechanical issues within the clutch assembly itself, possibly related to the dual mass flywheel, clutch disc, pressure plate, or release bearing.
Further investigation is needed to pinpoint the exact cause within the clutch mechanism of this Mercedes W201. Understanding the interplay between engine speed and clutch release is crucial for effective troubleshooting and repair.
