The reduction of whining noise at higher speeds may be due to the noise being masked by wind noise, engine noise and tire noise.
If it sounds and behaves the same as the gearbox bearing noise, then it's probably the gearbox bearing. A bearing can fail in 10K Km due to bad installation, a lubrication problem, low quality parts or just plain bad luck.
If your previous repair came with a time or mileage warranty, you should think about making a claim for a free repair under warranty.
You want to pinpoint the sound and make sure it is coming from the gearbox? Good idea! Get a length of corrugated plastic hose, perhaps 25mm (more or less) in diameter and 5-8 meters in length.
Also get some string and some duct tape or any strong adhesive tape. Put the vehicle on ramps or raise the vehicle by another means. Get under the vehicle and tape (or tie with string) the end of the plastic hose onto the gearbox. If possible, arrange it so the open end of the hose is directly on the gearbox housing.
Now route the hose to the passenger window, taping or tying the hose to the bottom of the vehicle about every 30cm. Keep away from any moving parts, tires, etc. When the hose reaches the area of the passenger door, if you want it to be attached to the vehicle, it may be best to use masking tape on the car body instead of duct tape, to protect the finish.
Route the hose into the passenger window. Ask someone to take you for a test drive while you listen for the bearing noise with the end of the hose on your ear. If the noise is coming from the gear box, it should be extremely loud in your ear. If it is coming from something else, the noise should be almost absent from the hose.
If the noise is absent, attach the hose to anything else that you suspect of making the noise and repeat the test drive.
Good luck!
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