Transmission Slips When Gwar Number Indicator Blinks

My 2004 Mazda 3 Sedan (GT or GX) has a problem with the transmission. Not entirely sure if it’s the transmission or maybe something else like a sensor. Once I start going it seems to have a rough shift from 2nd to 3rd. Once it gets to 3rd and 4th gear only is when the gear number indicator on the dash will flash off. When it’s in 4th gear and it flashes off it will downshift to 3rd. I’ve also noticed when the gear number indicator starts doing so if I lightly keep my foot on the gas it’ll pop the 4th gear back up and stay on while I very lightly push to keep the car in a acceleration. Don’t know if this matters but also another thing my reverse lights will not come on either. I’ve replaced both the bulb and the fuse. If anyone could help it’d be greatly appreciated! First time posting hope I did everything right.

Sounds like you’ve got a mix of issues, but they could be related. The flashing gear indicator and rough shifts between 2nd and 3rd might point to something like a bad speed sensor, shift solenoid, or even low or dirty transmission fluid. Since it happens in 3rd and 4th gear, it could be something specific to a solenoid or a pressure issue in the transmission. The reverse lights not working makes me think of the neutral safety switch (NSS), which detects gear positions it could be failing or misaligned, causing both the light issue and possibly affecting the shifting too. I’d start by checking the transmission fluid to make sure it’s clean and at the right level, then scan for any codes since the flashing gear indicator usually means there’s a code stored. If that doesn’t help, look into the NSS or the solenoids inside the transmission.