Best of Deals Car Reviews Repair Shops Cars A-Z Radio Show

Whining noise in the rear end of my 2008 Subaru Forester

It happens when I accelerate from 10MPH up to about 70MPH and then is intermittent at higher speeds. The volume and pitch of the whine is constant the whole time I am accelerating. If I brake while accelerating the noise does not change. It is a very high pitched noise almost to the point of being out of range for the ear to hear. The noise is so high pitched that it is hard to determine exactly where it is coming from except I fell like it is behind me. Cornering doesn’t seem to make a difference. I hear it most when I start my commute getting onto the freeway, I have also heard it when I do stop and go while running errands. Anyone out there that can throw some light on this problem?

Does it make noise when the car is in park. Does it whine if you press the gas pedal while in park.

I will try that and let you know.

Check for any leaks from your rear differential. You need to narrow down where the problem is. If there is a leak then you may need to replace the seal or gasket to the problem area. It sounds like your low on fluid. The gears in the rear diff of your car are helical which means cut at an angle. When low on fluid this can cause a whining noise as you increase speed due to the gears not being lubricated.

If I am leaking differential fluid should I expect to see a stain on the garage floor under the differential? I don’t think I have ever seen a stain there.

You’ll need to go behind your car and look underneath it. The leak may sit high enough so it doesn’t leak while sitting and there’s no pressure when the car sits. While in motion it can leak because the build up of pressure. Like cam or valve cover seals in your motor.

Unless you’re sure it’s from the rear, I had something similar which went away when I had the belts changed.

My 2006 Forester also makes a high pitch whine when accelerating. Was told it was probably an air leak. Does that make any sense or should I be looking for another problem?

High pitch noise can be many things. Vacuum leak is easy to find though. Get a can of brake cleaner and spray around the vacuum lines while the engine is running - DON’T SPRAY AROUND ANY WIRES… If the engines idle changes you found your leak. power steering pump can cause this so can a transmission. Anything that is hydraulic can make this noise when you get air in the line. A gear to gear timing and at times a chain or belt also. check your transmission fluid. Does it smell burnt or have deposits on the dip-stick. If you have a manual then it could be the clutch pack going bad though generally speaking it would sound different smell bad and slip in gear.

High pitched whines coming from the rear end of a rear wheel drive vehicle mean the rear differential fluid level and fluid quality be checked as first priority. If it is even a little low, or has water in it, continuing to drive may cause expensive damage to the differential unit. This is something you don’t want, so checking the fluid is well worth the expense. Also, if the rear axel has been underwater even briefly , like if you were on a camping trip and needed to cross a stream, replace the differential fluid with new at earliest convenience.

Toyotatalk is right - it could be from anything that has gears. In my case it was the transmission in my 01, which when removed, showed that something had been chewed up inside, and the fluid had become a strange consistency. Replaced it with another of low mileage and it has run another 100,000 since then.

I also have a 2008 Forester that started making a whining at the rear end. I took it in and was told it was a wheel bearing. The noise is still there after they replaced the bearing. I think after reading this thread it is the differential. It is not brake noise. I have a standard transmission. The tires are properly inflated and rotated regularly.
I hear the noise mostly around 40mph when decelerating. Turning makes no noise and there is no wobble that I am aware of.
Not to confuse the issue, the sound is a bit less noticeable after the wheel bearing replacement but I think that is because temperatures have dropped 25+ degrees just since the work got done.
My question - differential? If so, what do I say to the mechanics that charged me $450 to replace a part that might have been worn (100k on the car) but not in need of replacement and who will certainly want to charge me to do something to the differential (put in oil?)
Thanks for your help!