Differential Noise - Will fluid change help?
 

I have an 06 E53, 122k miles

It has some bearing noise in the rear diff.

It's not super loud, but on a 1700 Mile road trip, competing with road noise, I particularly noticed it around 60mph and especially on Deceleration.

I bought the car with extended warranty so I took it to one of the warranty companies shops. They said the whole diff needs to be replaced. Warranty denied the claim because I do my own engine oil changes. Has nothing at all to do with differential failure, but it's their loophole to get out of paying claims on powertrain items now.

I talked to the mechanic and he said the bearings are "gone" and my cheapest bet is to throw a used differential in there.

However, I'm wondering, given that the mechanic never opened anything up for visual inspection, and that the noise isn't overbearingly loud, if changing the fluid would help the situation? Or at least add longevity to the car so I'm not in a rush to source a differential and install it?

Is it worth doing a fluid change at this point?

We have another 1700 miles to go next week to get back home...

Pretty low miles for a diff failure but I don't know what engine you have...

It might be low on fluid, in which case a fluid change WILL help (as long as it isn't leaking badly). ;)

Given the low cost and relative simplicity of a rear diff fluid change (about 1.4l 75w-90 Synth plus a cheap fluid pump) it might be a good idea to change it before heading home. At least that way you know where you're at with it.

That's my thought too. It's a 3.0i motor and the vehicle has been horribly neglected by past owners. That said, I don't really know how you can neglect a differential that doesn't require maintenance for at least 100k miles, so I'm hoping it's something I can at least prolong for a while.

Is there any benefit to going with 75w140 if it does happen to be bearings? Or would 75w90 suffice?

And I don't have access to a new drain plug or o-rings where I am. Will I have leak problems by reusing the original? Or should be it ok?

Thanks!

It's only a WAG on my part but I'm thinking the 75w-90 should be fine. At least then you know the fluid is right and good.

Don't need new drain plugs etc. - I've changed both diffs and transfer case (transfer case uses BMW power divider oil, not ATF) and never replaced the plugs etc. - zero issues.

Noise might not be diff as the driveshaft centre bearing (CSB) sometime makes a similar noise. Sounds like a diff though, from the fact it changes under deceleration.... :(

Definitely yes, try just changing the oil. Stick with the spec, which is probably about 75W-90.

When I got my 2001 3.0i with about 160k on it, I don't think the front diff fluid had ever been changed, and the rear had probably been changed once. I think due to the stiffening plate cover there, it is an easier thing to skip. And BMW specified lifetime fluid there, so in theory no need to ever change it.

Driving the car home after buying it, I could hear what I thought was front diff noise, and never heard that again, after changing most of the fluids pretty much as soon as I had it in my driveway.

And I reused the drain and fill plugs. Nothing blown up yet. I promise to update this post if that ever happens.

Some more details are coming back to me now ... I think since the front fluid was so dirty looking (and even smelled a little burned), I changed the fluid, ran it for a week or so, and then changed it again. Glad I did that.

And I even found my notes on that: 700 mL Valvoline syn 75W90 GL-5. Drain and fill plugs are 14mm Allen, 60 Nm. Re-used Aluminum gaskets. Of course, you should never reuse those gaskets unless it's much more convenient than the alternative.

And of course to get at the front diff _almost_ requires removal of the stiffening plate. Far easier to get at if you just remove that plate. But whether to re-use the 6 bolts (like I did) is a controversial issue.

Here we go again [emoji897][emoji1787]

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The BMW Diff is known to last some 300K or more.
My 1998 528i rear diff is still good at 180K.

For front and rear diff, I use Redline 75W90.
Detail in the link below:

https://xoutpost.com/bmw-sav-forums/...se-fluids.html

You can use suction gun (as in the link above)...or
By Gravity!

Gravity method is via a clear tubing as in the link below I wrote some 13 years ago for my 1998 528i:

REAR Diff & MANUAL Trans Fluid Change: Tips and Tricks

Hope for the best, but prepare yourself for the worst. Even though a differential doesn't require a lot of maintenance, it does require the fluid to be there. If the diff developed a leak and the previous owners ignored the leak, the diff oil could have leaked out so they were driving around on an empty diff. Doesn't take long for the gears in a diff to become burnt from a lack of lubrication. Does the diff makes a whining sound when you are on the gas but the sound go away when the truck is coasting? If it does, the gears are BURNT.

Sound also like the back lash is off probably due to excessive wear.