This leaves a real lot open to interpretation. A common set of symptoms includes a shudder or repeated jerking, but only between about 30 - 45 mph, only when accelerating lightly or cruising at a steady speed, and only once the engine is warmed up. If all of these conditions apply to your vehicle, the very common cause is use of the wrong transmission fluid. Different vehicles require different transmission fluids with special additives to prevent this shudder. It's caused by the torque converter's lock-up clutch trying to partially engage slowly to provide smooth engagement, but with an additive missing, it grabs too aggressively, then engine torque breaks it free for an instant, then it immediately ties to lock up again. That will happen three or four times per second.
The way to verify this is to hold the accelerator pedal and road speed perfectly steady when the shudder is occurring, then lightly tap the brake pedal for an instant with your left foot. That will cause the lock-up clutch to release, then reapply two or three seconds later. You'll feel that shudder stop for those two or three seconds. If you have a tachometer on the dash, you'll also see engine speed increase about 200 rpm for those few seconds.
This all assumes you have an automatic transmission. You didn't list the engine size or transmission type. If you have a manual transmission, those could have automatic transmission fluid or gear oil in them. Some can even be switched from one type to the other, but the special additives aren't a concern. For these, a worn clutch disc and possibly burned / hot spots on the flywheel are the best suspect. The shudder will occur at any speed, but will be much worse during the few seconds you're releasing the clutch pedal. When it occurs while driving at a steady speed, or when accelerating, it's because the clutch disc is worn excessively.
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Monday, March 18th, 2019 AT 4:31 PM
