A jerk or clunk when you shift from park into drive or reverse is usually caused by worn engine or transmission mounts, a high idle speed, low or worn transmission fluid, or slack in the driveline such as worn U-joints or CV joints. A jerk between gears while driving points more to the transmission itself: shift solenoids, low fluid, worn clutches or a control module that needs its adaptive settings relearned.
Jerks when shifting into gear
| Cause | Clues |
|---|---|
| Worn mounts | Engine visibly rocks, clunk from under the hood; see engine mount symptoms |
| High idle | Idle above normal, especially when cold; see idle air control |
| Low or old fluid | Delay and then a bang into gear; see delayed engagement |
| Driveline slack | Clunk from the rear on trucks; worn U-joints or a worn differential |
| Valve body or accumulator wear | Harsh engagement with full, clean fluid |
From park to drive or reverse
A firm engagement is normal, but a bang that shakes the car is not. With the brake pressed, shift into drive and watch the engine: if it rocks noticeably, the mounts are the likely cause. If the engine stays still and the clunk comes from under the car, look at the driveline.
From reverse to drive
Shifting from reverse to drive changes the load direction, so worn mounts and driveline slack show up most here. Coming to a complete stop before changing direction protects the transmission and the mounts.
Jerks between gears while driving
Harsh or jerky upshifts and downshifts are covered in transmission shifting hard. The usual causes are failing shift solenoids, low or burnt fluid, worn clutches and control module faults; see transmission solenoid symptoms and transmission control module.
After a battery disconnect or fluid change
Many modern transmissions learn shift timing over time. After a battery disconnect or repair, shifts may be harsh until the adaptive values relearn, which can take a number of drives. Some vehicles need a scan tool to reset or relearn them.
Does it get worse when warm?
A clunk that is worse with a cold engine often comes from the higher cold idle speed and thicker fluid, and usually eases as the engine warms. A jerk that gets worse as the transmission warms points more to worn internal seals or clutches, or to fluid that has broken down and no longer cushions engagement; see transmission fluid color.
How to narrow it down
- Check the fluid level and condition; see how to check transmission fluid.
- Watch the engine for movement while shifting with the brake held.
- Check idle speed and scan for codes.
- Inspect U-joints, CV joints and mounts.
If the transmission itself is failing, compare a rebuild with our transmissions.
More guides: 62TE problems · U-joint symptoms.
Trouble codes: P0700 Transmission Control System · P0750 Shift Solenoid A · all OBD2 codes.
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