[TheCoolX3]

Wondering if anyone else with a X3 35i 8- Speed auto has experienced this, In 1st 2nd and 3rd gear right before before and after I shift (Only notice this in Sport mode and Paddle shifting) I hear a faint yet noticeable high pitch whirl is the only way to describe it. It happens right around 3k.

I only notice it while under light throttle which leads me to believe that it has nothing to do with the extra power the car is making.

After about 15-25 minutes of driving I no longer notice the sound.

Any ideas at what this is? Could it just be because the tranny is cold? should I get a fluid change or flush?

[mbbx5]

I just did a mechatronic unit swap and after pumping in the first 4 liters following the procedure my transmission was making a noise as you describe until I completed the procedure and had the fluid level correct (about 6.5 liters went in). Maybe you should change your fluid just in case its low. A couple years ago my X3 was a little low on fluid because something cracked the plastic filter/pan. The leak was not obvious because it was slowly dripping on the splash shield covering the transmission then being blow onto the exhaust and burning off/blowing away.

[TheCoolX3]

That actually makes a lot of sense because I recently did a catless downpipe install and saw a little fluid leak but thought nothing of it, Ill inspect it further and take it to BMW if needed.

Originally Posted by mlidz

I just did a mechatronic unit swap and after pumping in the first 4 liters following the procedure my transmission was making a noise as you describe until I completed the procedure and had the fluid level correct (about 6.5 liters went in). Maybe you should change your fluid just in case its low. A couple years ago my X3 was a little low on fluid because something cracked the plastic filter/pan. The leak was not obvious because it was slowly dripping on the splash shield covering the transmission then being blow onto the exhaust and burning off/blowing away.