[bmwx32015]

So I took my out-of-warranty 2015 X3 xDrive28i to a very trusted indy shop specializing in BMWs only to check for a strange lightly whistling noise that would appear when I press the gas pedal even if slightly. Verdict - whoever replaced your rear differential (it was replaced by dealer during warranty period 3 years ago) never put an oil in it... They specifically stressed that it is not a leaking problem but the luck of oil at all. I always followed all the required services and never missed oil change or anything else and X3 was driving normally until recently. So I was shocked to hear that. My commute is mostly short drives (5 miles per day) in the city/town, once in a while highway drive.

I called the dealer who did the job - they refuse to believe that it is possible to drive that long without damaging rear differential and obviously hearing some bad noises. I have driven about 30k miles since the diff was replaced.

Is it possible to drive without oil in a rear differential w/o noticing that long? Or was it somehow leaked and any signs of leakage just been washed off by car wash/rain etc?

[e30lover318i]

It be impossible to travel 30k miles with no fluid in the rear end with out it making terrifying noises, and I don’t see the fluid getting washed away. You would of noticed the fluid in your driveway if anything.

[andreigbs]

The rear diff only holds 0.8L which isn't very much. How exactly did they check the fluid amount? I think the fill hole is on the side, and the fluid level would be below that fill hole, so it won't leak out when you open it up.

Experts, is this accurate?

[shumster]

I once messed up my diff fluid change on my RX8 (let it all drain out the bottom). It drove about one mile before locking up and destroying the internals. It was a very costly mistake

[pungo]

I diff with zero oil would make a hell of a whining sound and I don't think it would make it a few hundred miles, thought I don't know since I have no experience with someone driving without diff oil. I can understand if the oil was low, but with none, not going to get too far. If it leaked out, there should be signs of the leak since water is not going to wash it completely off. The method to check the fill level has been the same for many many decades so hopefully the shop knows how to check it properly.

[KC87ZB]

Originally Posted by andreigbs

The rear diff only holds 0.8L which isn't very much. How exactly did they check the fluid amount? I think the fill hole is on the side, and the fluid level would be below that fill hole, so it won't leak out when you open it up.

Experts, is this accurate?

Regardless of fill hole location the assessment is still the same. Small volume of fluid and diff is full when at the bottom of the fill hole.

I really don't know with this diff how low is too low but simple to get full.