Hi. My a170 cvt makes a buzzing noise. Seems to be directly driven by the engine cause reving in neutral the noise increases with rpm

The service and repair manual with diagram will provide you step by step help to locate and fix the problem easily and you will get the orignal factory manual from the given link Home Toolsnyou

does the buzz increase and decrease with engine RPM? if so a capacitor/filter is needed in the powering of that circuit (although that should not happen with a factory unit if installed as spec'd by the manufacturer).

check oil level in gear box as low levels can make the car rev up a bit but a small amount of reving is normal when being put into drive or put into neturel

There are a couple of things to check. If your power steering pump is low on fluid, or a bad bearing is in the Alternator, they will whine. The PCV valve or any hole in the Vacuum lines will whine as RPM is increased. Even having the Air filter box not fully seated will make a whining noise.

Now both automatic and manual transmissions can whine as RPM is increased. Check fluid for each.

Serpetine belt and pulleys-can make noise.

Sometimes you can shift into neutral at any speed and the engine rpm will drop almost instantly as the car rolls at speed. If the problem disappears as soon as the rpm drops, then an engine part probably is the reason.

I think you mean 3000 RPM right? Or are you talking about your idle, even still 300 cant be. Let me know...

This sounds to me as though you have a mixed up computer chip in the onboard computer controling the shifting. First though, check the RPM sensor on the tranmission. If it is sending a wrong signal, that would cause the shifting problem. If you have a digital dash and have an RPM display, with the car in Neutral, watch the RMPs while slowly reving the engine. If it seems not correct then replace the sensor. Hope that helps
ash?

exhaust has blown

If you have a CVT trans there is the problem the input bearing locks up. Unfortunatly there have been many problem with this rans for these symtoms. If you bought the vehicle new the trans is covered for life.

Check the front and rear differential fluids. you're probably need oil in the rear.

Check your transmission Fluid. Make sure your have the proper level in there, You could be looking for a new transmission soon.