Strange Transmission Noise at different speeds

I have a 2001 Hyundai Trajet 2.0 Auto.
When driving below 20mph all is quiet. Go above and a strange whine/vibration from the floor is heard. It gets louder upto about 50mph,
then goes quiet. Carry on speeding up and it comes back louder then quiet again at 70mph.
I have changed the transmission fluid but no difference. The noise is still there.
I thought bearings, but that would make noise at slow speed too, just to be certain, I jacked up the front of the car so the wheels are off the floor and stated her up. The noise was still there. So not bearings. Any suggestions.
Paul.
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Man, where is HyundaiTech when you need him?

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If this occurs in just one gear (such as second gear as sounds here), it's likely in the transmission. The bearing is probably loaded only in certain gears.
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wrote:

If this occurs in just one gear (such as second gear as sounds here), it's likely in the transmission. The bearing is probably loaded only in certain gears.
No its in all gears.
Slowly builds in volume from 0-50kph. Quiet at 80, then builds up to 115 and dies away 120kph and over
Its doing my nut in now.
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Any chance this is a four-speed automatic and the problem only occurs in first and third gears? (I know you've said all gears, but the speeds listed make me question whether that may not be the case.)
You could have a problem with a drive shaft, differential bearing, or hub bearing. Any of these issues would be likely to continue making noise with the drive wheels off the ground.
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