When I lightly accelerate and the transmission downshifts I hear a growling noise like it's struggling to downshift. It does this in all gears. If I give it more gas or downshift manually it shifts just fine. I've regularly had the fluid changed and just had it done again and it doesn't seem to help the problem. Other than that it works perfectly, surprisingly good for 130,000, but this problem is steadily getting worse. Any ideas?

 

Anybody?