Whistling noise when reversing?
 

I have a 98 honda civic 1.6L 4 cyl with 5 speed tranny. A whistling noise happens only in reverse and the fluid level is fine in the transmission and it is new fluid too.































Any ideas? Maybe a bearing?

maybe your ground is messed up and the sound is coming from your stereo speakers. or maybe a vaccum line.

the gears are straight cut. this should be normal if it sound more like a whine!

LOOOOOOOOOL..... It's normal.
Manual Transmissions do that. On ALL cars... the SAME amount. That's the way it is. The implementation of the reverse gear is usually different, implemented in the following way to reduce the cost of the transmission. Reverse is also a pair of gears: one gear on the countershaft and one on the output shaft. However, whereas all the forward gears are always meshed together, there is a gap between the reverse gears. Moreover, they are both attached to their shafts: neither one rotates freely about the shaft. What happens when reverse is selected is that a small gear, called an idler gear or reverse idler, is slid between them. The idler has teeth which mesh with both gears, and thus it couples these gears together and reverses the direction of rotation without changing the gear ratio.