Transmision noise Voyager '89 2.5 Turbo, 3 speeds

Hi all,

Plymouth Voyager 89, 2.5 Turbo, 3 speeds

Since a couple of week I have a sharp noise and a small vibration when
the car run higher than 60 Km/h.
In the last days the noise becomes to be more and more accentuated.
Initially I supposed the noise is coming from the bearings.
I changed both bearings, but the noise persists. I changed also the
axels one year ago, don't think the noise is from axels.
If I run at more than 60 Km/h and put in Neutral, the noise is still
there even than the RPM come to 8-900 (idle), until the speed is less
than 55-60 Km/h. If I stop the car, put in Neutral and I accelerate
up to 3-4000 RMP, there is not this noise.
Someone told me the noise is coming from automatic transmission.
I changed the fluid myself each year (ATF3+ for Chrysler ) and
adjusted bands (at correct values with a dynamometer wrench torque) ,
the fluid is not smell as burn and the level is OK.

Any ideas, please.
Thank you,
Chris