I have a 91 ef civic with an integra trans and a b20. I just had all the bearings replaced in the trans becuase of this sound. Reinstalled it and a new throwout bearing still whined. Took it apart again and found a seized pilot bearing. Reinstalled today and its still whining. The sound can best be described as a straight cut reverse gear like sound. Clutch postion does not matter it only happens when off the gas, like coasting in neutral or engine braking. Please help im stumped. I would like to rule out everything before blaming the trans guy.

 

I once towed a Uhaul trailer about 1500 miles in my old crx si. It chewed up the side bearings, and got hot. I replaced the trans with a different one, but then eventually replaced the bearings in my original, and installed it back in the car, after rebuild it always had a whine same as you describe only when coasting and only when off the gas. drove it like that many many thousands of miles, until i finally sold the car due to rusting of the body. car had 292k something miles last i knew and still going.

 

i had a similer problem as well but it was the reverse also back in the day when i had my 90 crx si
the fix was a pcv valve that was clogged