Bobcat T590 noise in reverse

[FWD]

I have had a 2018 Bobcat T590 since it was new, now having about 160 hours. At around 40 or 50 hours it started making a "what I call" a noise in reverse similar to the noise it would make going into a pile of gravel for a bucket load similar to just before stalling out. Everything on it works fine and when it makes the noise kike I stated it is not out of power. It will back up fine with a loaded bucket going up hill, just kind of noisy. The noise is less as the hydraulic oil warms and when it is real warm, (not hot) the noise is bearable vs when you first start out at maybe 40 degrees. I changed both filters which had no visible metal and it made no difference. You can't hardly hear any noise standing next to it while someone else is operating it. I brought it to my dealer and they don't think anything is wrong. I was thinking of trading for a different brand, but the dealer tried it a bit and didn't like the noise, of course it was about 40 degrees then. Any ideas?
FWD

 

[KSSS]

It sounds to me like it is going over relief if the sound is the same as it is going into a pile. Those machines easily go over relief just looking at a pile. You might try replacing the hydraulic oil. BC shows 3 different oil options, one is a synthetic, maybe that would be enough to quiet it. At least long enough to get it traded off if that is what you want to do with it.