Mercedes-Benz W140 automatic transmission harsh shifts
Why does the W140 automatic jerk or shift unevenly?
The most common causes are too much fluid, vacuum hose leaks and a worn transmission. Start with the fluid level and the vacuum lines, because they are the easiest to check.
How does the fluid level affect W140 automatic shifts?
Too much fluid causes harsh shifts. Check the fluid level when warm. If the level is above the upper mark, it is worth removing some of the fluid. Changing only the fluid and filter does not always fix the fault.
How does vacuum affect W140 automatic shifts?
A hose runs from the rear of the intake manifold to the gearbox and regulates how sharp the shifts are. A leak in the hoses or in the gearbox vacuum capsules causes jerking, most commonly at the side of the intake manifold. An engine fault also shows up in the shifts.
Is a hard shift on a cold W140 automatic normal?
When cold, the gearbox holds the revs high while warming up, so the shift happens later at higher revs. That is normal. If shifts are still drawn-out or slipping when warm, the gearbox may be worn and need a spring kit or a repair.