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[Alex W]

I have a whine that must be coming from the diff. Its not a loud noise but it is annoying. The sound began suddenly from nothing a couple of weeks ago it starts at about 30/35 mph, below that speed there is nothing.

Tyres, brakes and wheel bearings all OK.

Question: Is this something that might be eliminated with a simple diff oil change or am I going to have to source a replacement diff?

[Alex W]

Actually its more of a hum than a whine

[chrisgixer]

I always wondered what happened to the noise to Bob Dents mv6. He thought it was dif whine, but I thought it was exhaust whistling. Tbh.

Maybe Jimbob will be along, as he owns the car now, last I heard.


Dif whine, I think 2woody said, relates to shimming of the dif. Iirc if its too tight it will whine. But I'm not sure I remember correctly. Far from it in fact.

[Alex W]

Thanks Chris, you seem to be suggesting that this hum is unlikely to be coming from the diff?

[chrisgixer]

There are other possibilities. But the first and easiest thing to do would be to check the dif oil level, as you suspect. There is a guide

[Entwood]

When I had the problem with noise from the rear, even Sassenach was unable to decide if it was bearing or diff related......

What I did, eventually, as I was fed up with people hanging out of doors/windows etc etc trying to listen and pinpoint the sound was ... jack the rear of the car up and place VERY SECURELY on axle stands, with front wheels very securely chocked ... use two bottle jacks under the shock absorber lower mounts to raise the rear wheels to a more "normal" position rather than "hanging" on the drive shafts - if that makes sense.......

Start up and place in drive ... due to no load the auto box quickly ran through the gears and settled at around 20 mph, at tick over, and the noise was audible .. so under the car I went and listened ... immediately obvious it was from the diff area .. but just to be sure I pulled on each handbrake cable in turn to stop one wheel .. no change to the noise ruled out wheel bearings.

Diff was replaced with a known good used one (thanks to Rob in Bristol) and the noise just went away ..

Some folks have said it was reckless to go under the car with it in gear, engine running, rear wheels off the ground .. but taking a great deal of care and using some basic common sense, IMHO it was no more dangerous than being under the car dropping the diff itself ...  in fact that hurt far more when it rolled off the jack and I - stupidly - tried to catch it one handed ... which was never, ever, going to work .....   


 

[Jimbob]

I always wondered what happened to the noise to Bob Dents mv6. He thought it was dif whine, but I thought it was exhaust whistling. Tbh.

Maybe Jimbob will be along, as he owns the car now, last I heard.


Dif whine, I think 2woody said, relates to shimming of the dif. Iirc if its too tight it will whine. But I'm not sure I remember correctly. Far from it in fact.

Bob Swapped the Diff, and the noise changed....But it still whines.

Exhaust has been changed as well now, and the whine persists.

Its there from about 30 mph when accelerating, ease off and the noise dissapears.

[zirk]

Diff whine will get better or worse when cornering, is the whine still the same when coasting down hill?, dont rule out rear wheel bearings, especially on Estates.   

[biggriffin]

First thing to do,is change the oil.. And use a synthetic one to.

[Kevin Wood]

Diff whine will get better or worse when cornering, is the whine still the same when coasting down hill?, dont rule out rear wheel bearings, especially on Estates.   

I've found diff whine is normally sensitive to load. - i.e. it might be there only under load or engine braking, but not there when coasting, or vice-versa. Sometimes, it's just always there, though.

[Alex W]

The hum starts at about 30mph, it is not loud at first, people who don't know what the car should sound like, have trouble hearing it. It increases in pitch and volume with acceleration. It is still present when coasting in neutral. It is no different when cornering or when accelerating rapidly (I don't normally spank her, she's getting old, but today I tried it  - and she seemed to enjoy it).

The car passed its MOT yesterday and the garage say the wheel bearings are OK.

Since the sound began the rear brakes have been overhauled (new Shoes, Pads, Discs, springs, fitting kit), No change to the hum but the brake rattling and clonking has gone. Lovely.

It looks like the first step is to try a diff oil change.

The maintenance guide gives two grades of oil depending on your diff type but I understand that you can't tell what type of diff you have (LSD or not) until you take the cover off, if that is true, is there a type of oil that will suit both so I can buy it in advance?

[Kevin Wood]

You can be pretty sure it's not an LSD, so any EP90 oil will be fine.

[Keith ABS]

  Could it be a tyre related problem?
Keith B

[VXL V6]

The diff in my 2.6 was rebuilt because the pinion bearings on the input were worn, I guess as a result of a fluid leak that was left without replacing the seal allowing the diff fluid to absorb the swarf from the bearings and become a fluid abrasive.

The noise was a metallic speed dependant noise that you just couldn't ignore!

[Alex W]

  Could it be a tyre related problem?
Keith B

The tyres are in good condition and although they are cheap tyres there is no reason to suspect they are the cause of the noise which started suddenly, like flicking a switch. I drove two miles to drop off my daughter, on the way there was no hum, I turned around to come home and the hum began on the return journey.