[YunzyE90]

Hi Guys.

I drive a 09 E90 318i.

I started to hear a noise coming from the rear, a local specialist told me it’s the rear differential. So it’s out, and I’ve given it to a gearbox/differential specialist in the Midlands called PowerGears to recondition.

I asked what’s the process, he said we replace the bearings and seals along with a few other things I can’t recall but he didn’t mention gears, thus I asked him what about if the gears are damaged. He did say it is very rare the gears are damaged in the differential, and it’s usually the bearings and seals, and IF, the gears are damaged, I would here louder clunking and clicking sounds (which I don’t hear which is good, I guess). Also, if the gears were damaged it is not repairable as BMW do not supply the gears for this differential.

(FYI. I only hear a sort of metallic whine, rattle kind of noise, this is on both acceleration and deceleration, please see the attached video)

However they said it won’t be stripped until tomorrow, therefore will not know if there is any damage on the gears until then. I’m hoping it’s just bearings and seals.

The specialist is very sure it will only be bearings as he’s never seen gears damaged on the diff before, and that it is very rare, and will be making much more prominent noises.

So I’m on the forum to see if anyone knows the difference in differential noise when it’s just the bearings and seals or if the gears have also become worn and gone bad.

Please watch the video below and reassure me if it is just bearings/seals or is it gears too.

[e90yyc]

I’m not an expert here but I’ve never heard of damaged gears in an E90 diff. As your mechanic points out, bearings are the likely culprit here. Also makes sense to do the seals since they’re cheap and easy.

It sounds like you’ve already got the repair in motion, but personally I would just buy a good condition used diff and put it in. They’re cheap, and because they don’t commonly fail it’s not a big risk to buy used.

[YunzyE90]

Originally Posted by e90yyc

I’m not an expert here but I’ve never heard of damaged gears in an E90 diff. As your mechanic points out, bearings are the likely culprit here. Also makes sense to do the seals since they’re cheap and easy.

It sounds like you’ve already got the repair in motion, but personally I would just buy a good condition used diff and put it in. They’re cheap, and because they don’t commonly fail it’s not a big risk to buy used.

Thank you for your reply.

To be honest, I have heard they are quite a common problem? As from manufacture they used cheap/ball like materials which ultimately lead to the failure of many diffs on the E90. I’m no expert too, what so ever haha. But yes it’s already in motion, I thought reconning a diff is a better option? As bearings and seals will be brand new. I am being charged £300, so average price really. And the risk you run with buying a second hand diff is you have no idea when it’s going to go again. Giving the mechanic a call tomorrow, let’s just hope it’s only the bearings and seals, not the gears!

[TunafishE93]

If they are only charging 300 then that's a steal, or are you talking that's just the parts cost (which is about right). Those bearings are pricey, I put a LSD in mine and the bearings were the sticker shock since you can't reuse them with and new LSD doesn't come with them.

It sounds like the shop knows what they are talking about, the gears you can't get from BMW and they don't even have part numbers for them. Just by the way, its the bearings causing the noise not the seals, but you replace the seals when you do the bearings.

[YunzyE90]

Originally Posted by TunafishE93

If they are only charging 300 then that's a steal, or are you talking that's just the parts cost (which is about right). Those bearings are pricey, I put a LSD in mine and the bearings were the sticker shock since you can't reuse them with and new LSD doesn't come with them.

It sounds like the shop knows what they are talking about, the gears you can't get from BMW and they don't even have part numbers for them. Just by the way, its the bearings causing the noise not the seals, but you replace the seals when you do the bearings.

Yes, £300! I believe it’s pretty cheap labour, and mainly part costs. Oh okay. You see I have no mechanical background, most of my questionable knowledge comes from what I’ve been told and these forums haha! Also, did you listen to the video? Would you say it’s bearing noise? And no gear damage?

The purpose of this thread was to mitigate any chance it is the diff gear damage .

[TunafishE93]

Gear damage could happen but without tearing into the diff its hard to say. I would say its uncommon, the ring and pinion is pretty strong.. The main thing is getting the backlash set properly.. I have broke axles from torque and never had issue with the diffs gears (not bmw) so they can hold up pretty well.

[F31B48]

Originally Posted by YunzyE90

Thank you for your reply.

To be honest, I have heard they are quite a common problem? As from manufacture they used cheap/ball like materials which ultimately lead to the failure of many diffs on the E90. I’m no expert too, what so ever haha. But yes it’s already in motion, I thought reconning a diff is a better option? As bearings and seals will be brand new. I am being charged £300, so average price really. And the risk you run with buying a second hand diff is you have no idea when it’s going to go again. Giving the mechanic a call tomorrow, let’s just hope it’s only the bearings and seals, not the gears!

Yes you are right, it's a common issue with 4 cylinder diffs. They're pretty rubbish. 6 cylinder diffs (except 323i) are pretty much trouble free.

[e90yyc]

Originally Posted by EvaBmw

Yes you are right, it's a common issue with 4 cylinder diffs. They're pretty rubbish. 6 cylinder diffs (except 323i) are pretty much trouble free.

No doubt! Thanks for the info. Didn’t even cross my mind but of course they’d be using different diffs…

[mainbearing]

When it is fixed, change the oil regularly (none of the "lifetime fill" stuff, at least in the States) and make sure the differential is filled to full.

[YunzyE90]

Originally Posted by mainbearing

When it is fixed, change the oil regularly (none of the "lifetime fill" stuff, at least in the States) and make sure the differential is filled to full.

Hi guys, an update.

So the diff specialists stripped apart the diff and said the gears are fine, great news. However, they also said the bearings and seals were fine too, not much wear at all (well, if any concern). They said overall the diff was fine, if course however they replaced the bearings abs seals anyway as the diff was already stripped. The oil was not low too.

So what could possibly be causing the noise above?

A potential reason may have been that I just pretty much spotted it very early. As the noise wasn’t very loud inside the cabin, most casual drivers may not have even noticed the noise, I’m just sensitive to noises and paranoid, maybe I spotted it very early hence why the bearings weren’t badly damaged?

The diff hasn’t been put on the car yet, so will update tomorrow if the noise is still there.

Note: when car was on the ramp (before the recon took place) the noise was most definately coming from the rear differential. The mechanic can say He’s 100% sure of it. Therefore, very peculiar the diff was in a good condition when stripped!

[R3dLeader]

Originally Posted by YunzyE90

Thank you for your reply.

To be honest, I have heard they are quite a common problem? As from manufacture they used cheap/ball like materials which ultimately lead to the failure of many diffs on the E90. I’m no expert too, what so ever haha.

In fact it is the opposite, the angular contact ball bearings used on the pinion shaft are more expensive than traditional taper roller bearings. Ball bearings are used for reduced friction which results in better gas mileage. Durability suffers a little bit with the ball bearings.

OP, have them closely inspect the wheel bearings and driveshafts as those could also be the source of the noise.

[YunzyE90]

Originally Posted by R3dLeader

In fact it is the opposite, the angular contact ball bearings used on the pinion shaft are more expensive than traditional taper roller bearings. Ball bearings are used for reduced friction which results in better gas mileage. Durability suffers a little bit with the ball bearings.

OP, have them closely inspect the wheel bearings and driveshafts as those could also be the source of the noise.

Shafts have been inspected and their fine. Further to this, I will ask about wheel bearings tomorrow, however, I doubt it is as the noise increases with acceleration, a metal rattle/whine sort of noise. I honestly thought it was gearbox, but it’s coming from the rear of the car, and “travelling” towards the front. Therefore if it’s originating from the rear, no chance it’s a gearbox issue, which is of Course good.

But we’ll have to see if the noise goes when the diff is back in tomorrow

[Johnnie777]

Good ideas here

[YunzyE90]

UPDATE: turns it it was the rear diff, I just spotted it fairly early, hence why the bearings weren’t as shagged. As when most people get the diff reconditioned the noise is either very loud or the diff has failed completely! Haha! Sometimes being paranoid works out 🤔

[Ozzie335i]

Pay 'em 300 now vs 1200 later. While you claim not to be mechanically experienced you knew enough not to let something get worse, and potentially more costly.

[YunzyE90]

Originally Posted by Ozzie335i

Pay 'em 300 now vs 1200 later. While you claim not to be mechanically experienced you knew enough not to let something get worse, and potentially more costly.

You’re right man! Paranoia pays off haha. When the recondition mechanics told me there was nothing wrong with the diff I was thinking, what could be wrong then? As when the car was on the ramp, 100% the noise came from the rear differential.

They were eager to say it isn’t the issue but they of course reconditioned it anyway new bearings and seals, diff is back on the car = noise is gone.

And no, the oil wasn’t even low, so weren’t that.

Genuinely believe I just spotted it very early? As most people may leave it till the car is isnt drivable or The noise is crazy loud.

[Costafortune]

Pinion bearing wear and failure is common on these diffs. It's worse on later ones that use Koyo bearings from around 2008 onwards. You can buy a good used diff these days for around £300 or less so it's not always worth rebuilding a knackered one.

[Costafortune]

I should add, I always have good used diffs for around £250 and can get them fitted for £70.