A humming sound when moving off from stationary

[rs237]

Hi all,

I have a Lancer Activ 2012 CVT 2ltr which has done 58,500 kms. Last year I got the CVT fluid changed at 48,000 kms as I the tranny used to whine when going uphill. It has been ok ever since. Now from last few weeks as the weather has started to warm up I have noticed that a humming sound comes when the car has warmed up and when i move off from stationary. The sound then goes away when the car has picked up speed. There is no loss of power and no shudders from the transmission. Also when the car has driven for sometime and i turn it off, then turn it back on in Park mode, the humming sound comes and goes away as the RPM settles after ignition. Then comes up again as i move off.
Seems like its coming from under the car, so i suspect it could be the cvt. Does anyone know what this could be?

Cheers!

[rs237]

Any comments anyone?

[sarusa]

Sorry no idea!

[Quismiff]

Might be time for a CVT service, there is filters, and o-rings to change, the valve body could probably need a clean, A mate in NZ reco'd his CVT/Auto tranny 6 years ago and still goes like new, you may not have to go that far, but a good flush won't hurt, as there is an oil cooler for those things I believe. I see it has only been 10k km since you changed the oil, but how long before that since it was changed? and what is the service interval?

[lancerdarryl]

It's extremely hard to diagnose a sound over a written forum,it may be something as simple as a noisey drive belt pulley.Best bet is to take it to a couple of good workshops and have them take a look and listen.

[rs237]

Might be time for a CVT service, there is filters, and o-rings to change, the valve body could probably need a clean, A mate in NZ reco'd his CVT/Auto tranny 6 years ago and still goes like new, you may not have to go that far, but a good flush won't hurt, as there is an oil cooler for those things I believe. I see it has only been 10k km since you changed the oil, but how long before that since it was changed? and what is the service interval?

The oil was last changed at some 50,000kms and now it has driven some 8000kms. What i suspect is that workshop that changed the oil used Valvoline Syncpower fluid. I went on Valvoline site and can only see a J1 spec. oil. There is no J4 spec. oil from Valvoline. I had asked the workshop multiple times that did they use the right spec as per Mitsubishi and they said yes, yes.
The other thing is, if this was a sound from transmission then why doesnt the sound continue when the car is idling in P mode. When i start the engine in 'P' and when its hot, i get this humming as the revs rise and the humming goes away. I think it could be a belt or pulley as well?
Anyway, i am getting the car checked by Mitsubishi i dealer this Friday to see what could it be.

[rs237]

It's extremely hard to diagnose a sound over a written forum,it may be something as simple as a noisey drive belt pulley.Best bet is to take it to a couple of good workshops and have them take a look and listen.

Hi Lancerdarry, I also think it could be a belt or pulley as if its the transmission that makes the sound then that sound should continue to come when the tranny is hot and if there is definitely something wrong with CVT. Keeping in mind that if there something is wrong with CVT then the sound should be more frequent the more i drive.