NHTSA Complaint #11526108 — 2018 CHEVROLET IMPALA

While driving or idling (car in D/M, both automatic and manual), the car will rapidly shift to park and then back to where the shifter was set, usually in a lower gear that slows the car down or prevents acceleration. The transmission or speed sensor could be an issue. This can happen in rapid succession 3-5+ times in a row, which has led to a drop in speed from 65 MPH to 40 MPH, especially dangerous at faster speeds on a highway or when deceleration is occurring more quickly, like going up a steep hill. I am unsure what indication there is for cars that are behind me, but they have had to slow down or pass me in some instances to avoid hitting me. If it happens while turning at a 2 way stop or on an entrance ramp, my car might not accelerate fast enough to merge into traffic. There have been no lights on the dash, and the dealer has not been able to identify the issue when I have taken it in.