We need to start with codes if you have any. I would suggest stopping by a parts store and let them scan it for free if you can't pull them yourself.
Next this transmission was always sensitive to transmission fluid levels. It was common for it to have down shifting issues like you are talking about when the fluid was low. If the fluid is in good condition and proper level then you most likely have an issue in the shift solenoid and clutch pack. Basically the solenoid applies the clutch and they don't slip like they should and they just engage harshly.
Hopefully we have a code to confirm this, but even if not we need to dig deeper into which will require a scan tool. Let me know what you find with this and we can go from there. Thanks
Monday, March 9th, 2020 AT 3:17 PM