Diff for 2003 e85 with M54B25 at 3.23 ratio or diff rebuild kit

Z4ZeeGermans · Post by **Z4ZeeGermans** » Wed Aug 23, 2023 2:47 pm

To begin with the context: So I took my Z4 to the garage for a few repairs and the MOT a few weeks ago. One of the repairs I asked them was to replace the rear wheel bearings, as I already did the fronts, and there was a metallic whine in sync with wheel spin especially while reversing. I would actually like to take care of that myself, but as luck would have it I was busy with movig house at the time.

It turns out it's not the wheel bearings making the noise, it's the rear diff bearings... Funny enough, MOT does apparently not care for the state of the diff, so it's not even mentioned as an advisory

Anyway, I now need either a nice example of a 3.23 ratio rear diff (part number 7514149), or a bearing kit to fix it myself. Anyone have either of these?

: new (old) alloys too ^^; Z4.jpg (189.88 KiB) Viewed 592 times

Street · Post by **Street** » Wed Aug 23, 2023 3:56 pm

I have that diff, it’s been sat in my garage for 4 months.
£50. I’m up in the North East though so you might need to account for couriers etc. It’s pretty weighty!!

Z4ZeeGermans · Post by **Z4ZeeGermans** » Wed Aug 23, 2023 4:48 pm

Hi mate, can I ask what the mileage/model year this is? Or can you confirm the condition of it? (probably will be better than mine but oh well)

Spriteracer · Post by **Spriteracer** » Wed Aug 23, 2023 5:23 pm

If you can't find a suitable one you could try www.bearingkits.co.uk. I bought the kit for the coupe. Although I have stripped the diff I haven't fitted it yet. The chap there, Mark I think was his name, was very helpful and happy to chat if you needed advice.

Street · Post by **Street** » Wed Aug 23, 2023 5:28 pm

It came off a 53 plate with ~106k miles
Ex forum car if I remember rightly

enuff_zed · Post by **enuff_zed** » Wed Aug 23, 2023 5:42 pm

Tbh, for that money I would consider buying it, overhauling it and then fitting it.
You end up with a known quantity and your car is not off the road for long.
You'd probably then be able to overhaul the old one and sell that on as well.

Z4ZeeGermans · Post by **Z4ZeeGermans** » Wed Aug 23, 2023 9:42 pm

Yes I was thinking a similar thing. @Street, I'm not too south either here in Beverley, how much would it cost to send it over you reckon?

Street · Post by **Street** » Wed Aug 23, 2023 10:07 pm

I’d say it’s got to weigh a good 25kg+. We could try a Shipley quote to see if anyone would pickup? Drop me a message with your address and I could get a quote.

Although for a bit of petrol money I could meet you half way if you want to put it in the boot?

Z4ZeeGermans · Post by **Z4ZeeGermans** » Wed Aug 23, 2023 10:16 pm

PM sent

Z4ZeeGermans · Post by **Z4ZeeGermans** » Thu Aug 31, 2023 9:09 am

Didn't have the time to check it over but diff arrived! Thanks Chris

Street · Post by **Street** » Thu Aug 31, 2023 12:31 pm

Excellent. If you end up returning it I’d be interested to know how it goes. I’m interested in doing similar myself one day

Z4ZeeGermans · Post by **Z4ZeeGermans** » Thu Aug 31, 2023 6:02 pm

Well I have a bit busy few weeks ahead, so I'll get stuck in it afterwards. The plan is to swap this one in, open up the old one and assess any damage, and then refurbish it with new bearings. Will keep you posted

Z4ZeeGermans · Post by **Z4ZeeGermans** » Thu Jun 19, 2025 2:19 pm

Well... Turns out life has its way of getting in your way sometimes... Since I got this diff from you I got a section 21 eviction due to landlord selling the house, broke my arm (well, fractured), almost got deported because of a mistake my stupid employer made, and have been wating for a conclusion from solicitors, etc. everything finally finally is ok now, and I've started seriously getting into my Zed...

@Street, don't know if you give a toss after all this time, but contrary to what my local garage told me, I think my diff did not really have a problem after all.

I managed to remove it the other day and compared it to the one I got from you. Backlash and the operation of the flanges feel almost exactly the same. And better yet I still have a squeak on my rear drivers side wheel when it rolls. Means the diff wasn't the culprit.

Meanwhile I got in the mood of "while you're in there" and planned for a significant, if not major restoration of the underside. I'm not really documenting it but maybe I should start another thread somewhere.

I really want to drive this thing come July! She sat for more than a year at this point.

The diff below is the one from my Zed. Bearings look surprisingly in good condition (the car has 110k miles on the clock at this point)

I actually found a leak from passenger side output flange. Replaced both seals.

: IMG_20250617_135054.jpg (217.93 KiB) Viewed 79 times

: IMG_20250617_141211.jpg (120.21 KiB) Viewed 79 times

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NO LONGER WANTED Diff for 2003 e85 with M54B25 at 3.23 ratio or diff rebuild kit