Hello
Since i bought my Rx7 S5 convertible in 2016 i have always had a gearbox strange behaviour: i have a whining sound only on 1 and 2 gear but it whilnes for 0,5 seconds only when i shift gears (from 1st to 2nd and to 2nd to 3trd), no when it runs. With other gears i have no whining or whirring sounds even when i shift. Also at first when i bough the car the gears where hard to insert. Then i charged gearbox oil and i added an antifriction additive and now gears enter more easily but i have still this whining sound in 1st and 2nd gear only during shifting (i hear the sound when i press the clutch pedal) and only for 0,5 seconds.
What do you think about it? The gearbox works well and i feel no grinding during gears shift.

 

Another detail: when the car is parked at idle and i grab the shift lever with my right hand in the moment i slide the lever to the left and a little up just before inserting the 1st gear i hear clearly a "thump" sound from the gearbox, This thump sound is just before inserting 1st gear when i slide the lever up a little.