Z3 3.0i differential unit.

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Flight
Joined: Mon 16 Sep, 2013 20:43
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Z3 3.0i differential unit.

Post by Flight »

I intend rebuilding my diff during the winter, but as spares are very limited, and apart from bearings, are unobtainable.
With this in mind, does anyone know if our diffs are common to other vehicles in the BMW range. I believe a torsen LSD is fitted.
Many thanks
Flight
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Brian H
Joined: Tue 16 Dec, 2008 19:55
Posts: 2505

  Z3 roadster 3.0i

Re: Z3 3.0i differential unit.

Post by Brian H »

Looking at Realoem it seems that the diff is not a common part, have a look here.

http://2009.bmwfans.info/parts/catalog/ ... xle_drive/

If you click on the prt number it gives the option of usage.
kkkrisss
Joined: Thu 13 Jan, 2011 09:15
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  Z3 roadster 1.8
Location: Munich

Re: Z3 3.0i differential unit.

Post by kkkrisss »

E30 diffs are pretty much the same. I think the outer flanges are different but can be easily swapped.
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Southernboy
Joined: Thu 07 Oct, 2010 12:39
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  Z3 roadster 3.0i
Location: Johannesburg

Re: Z3 3.0i differential unit.

Post by Southernboy »

I believe I have seen "new replacement parts" on eBay. I thing the crown and ring gears are what was being sold. That may be of use if you need those parts. The LSD diff has 2 bearings. They are well worth replacing with a set of "matched" cup and roller sets. Matched means the bearing components are a matched set which were made for each other at manufacture. This is important so that there is a perfect marriage when fitted and the results will be sound mechanics for many years.

Output shafts are perhaps going to be the most difficult part to find without buying a complete spare diff and salvaging parts. If you go that route it may be best to have one diff fully reconditioned by a specialist shop, and sell off your "old" diff once you have the re-con fitted and tested. Selling your old diff will give you some return on investment. Alternately you could consider buying a really cheap "dog" and use it whilst your own diff is re-built to factory spec if you absolute need your car mobile. ?

This link might be interesting if it applies to your car...
http://www.ebay.co.uk/itm/BMW-LSD-frict ... 35ed770e21

and this looks very interesting at the price...
http://www.ebay.co.uk/itm/BMW-Z3-M-Road ... 35e644c3af
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c_w
Joined: Thu 19 Aug, 2004 16:50
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  M roadster S50

Re: Z3 3.0i differential unit.

Post by c_w »

Why are you attempting to rebuild it?

The 3.0 diff will be a Torsen LSD, so very rare in this diff as BMW didn't use this style LSD in anything else AFAIK. So no friction plates in them etc. You can have the bearings changed (but not a quick job as it takes some setting up by a professional to do it right), but can't think of any other parts you would need/want to swap on it. But these diffs are extremely strong and hardy, it would be rare to find one that needs rebuilding unless it's suffered oil contamination or something.

If you were to rebuild a clutch type LSD like in the M then you can get kits from http://www.driveandtraction.blogspot.co.uk/ think it is around £70.00 for new plates and dog rings. I fitted 3 plates in my diff when I rebuilt the LSD pack. Didn't touch the bearings as they are ok and my diff is from a 1980s e30!
Flight
Joined: Mon 16 Sep, 2013 20:43
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Re: Z3 3.0i differential unit.

Post by Flight »

Hi. All. Thank you all for your comments.
My reason for investigating my diff is to ascertain if my transmission clunk can be attributed to it.
I have tried to locate the source of this clunk for over a year, including a gearbox rebuild with new shift pins.
All that is left is the diff. I have heard it said that they all clunk, just forget it. However the facts are, they should not clunk, and if they do there has to be a reason. The car runs well apart from this noise, and I love it dearly but every time I hear this knock it reminds me there is a fault somewhere. The car is low mileage 35000 ish so I wouldn't expect too much wear, my money is on a design fault or a mechanical failure. Any how, we will see.
Best wishes
Flight
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c_w
Joined: Thu 19 Aug, 2004 16:50
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  M roadster S50

Re: Z3 3.0i differential unit.

Post by c_w »

It's tru they are prone to it. You will be disappointed when you spend your money - also not many people[companies] can rebuild these diffs despite what they may tell you and you may end up with a unit worse/with a short life.

In my experience the Torsen diff is slightly more clunkier than the others due to the amount of gears it has in it.
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Southernboy
Joined: Thu 07 Oct, 2010 12:39
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  Z3 roadster 3.0i
Location: Johannesburg

Re: Z3 3.0i differential unit.

Post by Southernboy »

Ah...the "clunk" issue..... There is absolutely no way the clunk can be completely resolved. Your concern is "BMW Universal" with regards the e30/36's. I know of a chap here in SA who had the diff re-engineered at enormous cost in an attempt to sort the problem. He had parts engineered with finer tolerances and although this reportedly improved the issue, it didn't remove it 100%. This was done on a brand new BMW.

I personally believe the issue is a combination of the diff and the prop shaft. The prop shaft has the rubber guibo which is fitted between the prop shaft and the gear box. This is a flexible coupling which absorbs transmission "shock" between the components in the drive train. As you can imagine, the torque forces involved on acceleration and deceleration have a "spring" effect as it twists this flexible coupling. I would take a close look at that guibo and assess it's serviceability, and perhaps replace it as a first step. Next issue is the splined linking joint in the prop shaft. This splined coupling has a little play. ie. from front to rear section of the shaft. The next 2 joints to examine are the 2 universal joints on the prop shaft to ensure there is no play in those. Finally the diff can be considered. The drive shaft to wheels is next. These also have a little play which is due to the diff internal gear components, plus the CV joints on these shafts.

The resolution the chap out here resorted to was to replace the diff, prop shaft and gearbox with Toyota components after spending thousands trying to resolve the respective BMW components. The benefits included a six speed box. Again, the cost incurred in fitting the Toyota box, diff etc wasn't cheap, but did ultimately satisfy the owner.
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gookah
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  Z3 roadster 2.8

Re: Z3 3.0i differential unit.

Post by gookah »

You could spend a lot of time and money chasing the holy grail, especially if trying to rectify a design fault.
spend the money on a louder stereo and enjoy the car with all its foibles... :D
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c_w
Joined: Thu 19 Aug, 2004 16:50
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  M roadster S50

Re: Z3 3.0i differential unit.

Post by c_w »

How the car is driven makes a big difference too, especially clutch control in first 2 or 3 gears.
Joycey
Joined: Mon 11 Jul, 2011 22:15
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  M roadster S52
Location: Basingstoke

Re: Z3 3.0i differential unit.

Post by Joycey »

I've been looking into this too. My LSD on my Z3M has started giving me some grief. I found one place with all the parts needed to rebuild the diff at www.bimmerdiffs.com but I couldn't find out the preload I needed on the pinion bearing. I think that bit of information would have to be trial and error.

So playing it safe I dropped it off to a guy in Hampshire who's doing a full rebuild for £240. Be the only job I haven't done myself on my M :lol:

Lee
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