AL4 Transmission Fluid Change

[Bvlet]

Hello everyone,

I'm a new member here in this forum and a passionate owner of a 2016 DS3 . Ever since I bought it new, I haven't replaced the transmission fluid. The current mileage is around 50,000 km.
Recently, I've noticed a bit of harshness when shifting into 3rd gear. Also, sometimes while driving at around 60–70 km/h, the transmission shifts from 4th gear down to 2nd, and occasionally even 1st gear.
The transmission is an AL4 4-speed automatic. Any recommendations regarding the transmission fluid and filter change? Is it necessary to replace the filter as well?

The following are my vehicle's specifications:

[myglaren]

Unfortunately your images can't be viewed in the UK

But you can upload them direct to the forum, a guide here.

[Kees]

An Al4 should do 250.000 Km without any problem, so this is strange for a car with only 50000 Km

[ozvtr]

sometimes while driving at around 60–70 km/h, the transmission shifts from 4th gear down to 2nd, and occasionally even 1st gear.

The transmission relies on information from the engines torque parameters as to when to change gears. While it's not a definitive answer, the problem might be with the engine and not the gearbox? Does this occur going up hills?

The transmission is an AL4 4-speed automatic. Any recommendations regarding the transmission fluid and filter change? Is it necessary to replace the filter as well?

The car and gearbox manufacturers both claim the gearbox is "sealed for life". Sorry but that's B/S!!! Consequently there are no official fluid change intervals.
The filter can not be changed without stripping the gearbox down! However a blocked filter is very rare in these gearboxes. You would start having other problems way before the filter clogs up.
Your car is now 10 years old. I personally would change the fluid now!