When I go at about 40miles(speed ) it's a loud the gears don't stick but the higher the speed the louder it get's need to kind of know what to tell a mechanic is to where to start to look.I doesn't

Noises are decieving. Cud be steering system or wheels or suspension. If ball joint fails car cud flip ovr.hav pro testdrive it. Seek a gudguy at surecritic.com

Check the flaps, could be sticking, or broken

I've just bought a K13 Nissan Micra and it doesn't sound quite right. The noise I hear also seems to be coming from the back but it sounds like when you chop down a gear in a manual going down a hill and the engine revvs, well this is the noise I get in the automatic speeding up and slowing down, even just cruising at a steady speed. Any ideas people? Apart from this noise I love this car.

Hello, Thought to have the differential lube checked? I had a 1994 Crown Vic and it had 161,000 miles on it when I sold it.

Although you need to reduce the overall speed, try turning your Overdrive button off and see if the noise goes away. The overdrive kicks in above 42MPH and if that is when your car starts to grind, its a good possibility for trouble.

Aside from that, the 3rd and 4th gear synchronizers or gears could be going. You could pull off the trans pan and see how much metal is in the pan.

You won't be going much longer if it is making this noise. Also try car-parts.com for Salvaged parts. It has an instant request feature and gives pricing, location, warranty, and contact info for all types of parts.

Vibrations usually don't make noise BUT, a bad hub bearing or a differential that is severely worn can.
Bearings generally don't both fail at the same time so if you hear the noise on one side more than the other, likely that one has failed. You should also check the diff fluid level. (low lube level will quickly destroy the gear set) I'd go as far as removing the cover and checking the gears and looking at the lube itself to see if it has any metal in it.
I could tell you much more by driving it but obviously I can't do that!!

You hear the engine or the transmission? If is the engine is doing it at all gears, if is only at third gear, is the transmission, change the transmission oil with a 80-90 or higher No. if still make noise, You have to open the transmission for service. Hope that help.

Somebody probably drained the front differential.

Sounds like the starter need to be replace or rebuilt.
The clicking is due to the starter still partially engaged. Grooves are worn on the contactors and the plunger is sticking in the starter.

What kind of noise? Humming? Screeching? Can you tell if it's coming from front? Left? Right? Does it get louder the faster it goes? Higher pitch?