hi there!

i would appreciate if anyone here knows whats happening to my datsun b310 a12 5 speed. its 4th and 5th gear produces a 'wuuuuuu" like noise at speeds around above 50kmh and the pitch gets louder as the speed increases in both gears. the 1st, 2nd and 3rd gear doesnt have this noise...even at 50kmh on the 3rd gear...

it has been going on for years even before the ride was handed down to me few years back and now its annoying me alot when i travel down the highway....i always need to blast the stereo to get rid of that noise

thanks guys for your answers

Sounds like it's time to pull this gearbox & either overhaul it before it destroys itself, or to replace it with a serviceable unit.
I suspect that you may have a bearing [or two] that is on its way out.

if its a 5 speed i would pull it out and rebuild it as they are rare gearboxes and u wouldnt wanna destroy it,

... or at least remove the side filler plug, and check the oil level. If it's low and you top it up, does the noise get quieter? If so, a rebuild won't be necessary (but would remove all the noise). The filler plug doubles as the level check. The oil should be filled until it just comes out of the filler hole (when car is perfectly level).

While we are on the topic, what is involved in a gearbox rebuild? Mine (60a 5 speed) is a little noisy in all gears and sinchro on 1st is pretty bad. Do you just replace bearings and sinchro's and adjust somehow for wear in the gearset?
Or do you have to buy new gears if they are worn?
How specialist is it? I have built engines before and had no problems with them, but this seems like it's a fair bit more difficult.

you got a noise maker and need to live with it (probably nothing at all wrong with it except gear wear)

i havent checked my gear oil for ages...gotta open it up to check how isit like on the next service. hopefully it'll damped the noise a little.

how i wish my car was quieter on the motorway...the roaring a12 + the noisy gb makes a noisy and uncomfortable journey...like somethings gonna blow up soon