For over 3 years, my 2001 Honda Odyssey transmission has had a whine, gradually increasing in volume . The pitch increases with speed, not RPMs, because it continues to increase pitch when it shifts and reduces RPMs. There are no performance issues, and there are no error codes when hooked to the computer. The transmission was put in at 93,000, 80,000 miles ago. Had fluid flushed and replaced with no effect.
79,000 miles ago is when you should have taken it back to the tranny place and complained to the shop about the whine.
Kind of late, at 80,000 miles and three years to bring it back now.
Other that doing regular maintenance …fluid changes and filter is about all you can do, other than replacing the entire tranny.
Skip the flush and just have a fluid and filter change. As many advocate on this site, "A flush is only to flush more money from your wallet. Same with engine oil flushes.
I hope you’ve been saving up for your next transmission 'cause this one is on its way to the Great Scrapyard in the Sky. That whine is telling you exactly that. Run it 'till she stops and replace this transmission with another.
You would be very hard pressed to sell this van to someone with hearing and you’d have to be morally bankrupt to sell it to the deaf without disclosing the noise.
I had a corolla with a similar problem and it turned out to be the differential.