Problems with Front Diffs?

[dubdub]

I dropped my car off at my independent BMW mechanic yesterday for a sound that I'd hear when turning at speed... over say 25 mph, you could hear a rotational noise turning right or left.

They had it all day and believe the sound is coming from the diff or TC. Tomorrow they are putting little microphones on it to confirm where the noise is coming from when the car is on the ground.

I have dealt with TC problems before, having blown one up after it developed a leak without me knowing... there were tons of threads on the internet about diagnosing and rebuilding TCs, but I have never heard anyone really talk about problems from front diff troubles.

Given that is mostly heard when turning, I would be surprised if it was the TC, given that only moderates front to back. In my head it wouldn't care about left to right (though I guess turning could place additional resistance on the drivetrain, forcing the TC to distribute the power front or rear, and that could be part of the noise)... what problems have people had with front diffs and what options might I have if they verdict comes back front diff?

[downforce22]

My front diff broke, but it literally had run dry, there was no oil in it. The spider gear broke and locked my front wheels as I was driving. It was pretty spectacular. I got lucky and was accelerating from a spot sign in my neighborhood on hard packed snow, so lucky it wasn't on the highway.

[flyboyx]

unfortunately, you haven't provided enough information to give any sort of opinion. did they run the car in gear on the lift? if so, was the noise present off the ground too?

it truly could be most anything. are you sure the noise is coming from the front?

it is too soon to talk about front diffs. but they are about 150 bucks used on this forum they do go bad often. usually the teeth break off the ring or pinon and get caught in the unbroken teeth creating a real f'ed up mess.

generally speaking, the tc(1) and the front diff(2) are the most common failure points on the car. usually they fail from neglect or abuse.

[dubdub]

Thanks.

After using microphones to identify the noise, it is the TC not front diff... but it only happens under load when turning. It is quiet if you just spin the wheels.

[spdracrm3]

well with the description you've given of when it happens thats when the Viscous Coupling and center diff (sun gears) are doing their job (outputs rotating at different speeds ),so its possibly one of those two items or a bearing/thrust washer thats under a different load while the VC is moving at different rates.how loud is it ,i know when parking my IX it makes a slight whining noise as the system loads up in tight turns only though

have you tried doing the jack test to see if noise is present (i know you mentioned only above above 25mph )but might be worth a try as an added diagnostic