Leaking rear diff

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Boosh
Joined: Sun 30 Nov, 2014 22:40
Posts: 324

  Z3 roadster 1.9i

Leaking rear diff

Post by Boosh »

Hi all,
My differential seems to be leaking, and it looks like it is the gasket failing. Is it just a case of draining the diff before opening it, spraying a good squirt of degreaser, wiping clean, applying new gasket from a tube, before closing up and refilling? If so, I'm tempted to have a go myself. Any special tools needed? Of course, I noted to loosen the fill-up plug first, to make sure I'll indeed be able to refill the diff at the end!
Thanks for your advice,

Boosh.
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Southernboy
Joined: Thu 07 Oct, 2010 12:39
Posts: 6436

  Z3 roadster 3.0i
Location: Johannesburg

Re: Leaking rear diff

Post by Southernboy »

You're about right about the simplicity and procedure of DIY. There is a paper gasket available from BMW which fits between the two surfaces. You will need that and some gasket sealer to apply to both metal surfaces before re-assembly. Bolts need to be torqued correctly. The paper gasket is really cheap from BMW. Check on realOEM for the part number etc.. You may as well replace with fresh diff oil at the same time, and also give the innards a good clean especially at the bottom of the diff case where gunk tends to settle. :wink:
"Normal is overrated"
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Boosh
Joined: Sun 30 Nov, 2014 22:40
Posts: 324

  Z3 roadster 1.9i

Re: Leaking rear diff

Post by Boosh »

Thanks, Barry,
I shall give them a ring about the gasket and enquire about the type of oil, though I had it flushed and replaced last year, so I should have the receipt in my files. How do I found about torque for the bolts? I've only got a long torque wrench, so I might have to invest in a smaller one, for I doubt access is great.
Thanks again,

Boosh.
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Southernboy
Joined: Thu 07 Oct, 2010 12:39
Posts: 6436

  Z3 roadster 3.0i
Location: Johannesburg

Re: Leaking rear diff

Post by Southernboy »

The bolts require 64nm of torque.
"Normal is overrated"
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Boosh
Joined: Sun 30 Nov, 2014 22:40
Posts: 324

  Z3 roadster 1.9i

Re: Leaking rear diff

Post by Boosh »

Human Z3 encyclopedia! Thanks again.
Well, I looked into it a bit more and put RedZed on high heels to have a proper butcher's from underneath. While it all in theory seems pretty straightforward, I'm a bit puzzled by the location of the diff hanging bracket: it is an elongation of the cover plate that needs to be removed in order to replace the gasket. The way I gather the job needs to be done is this: 1.- loosen fill up plug on diff, 2.- drain oil out, 3.- support diff with axle stand or similar, 4.-remove all 6 (16mm) bolts that hold the cover on the main body of the diff,5.- loosen bolt on hanging bracket, in order to: 7.- pivot cover off diff body. Then, clean mating surfaces and inside of diff, replace gasket with new one (€3.20 from BMW!), and put everything back together, tightening bolts in star pattern, then finally filling diff up with new oil.
I'm probably over-thinking this, but I'd rather plan ahead and do it right, than get stuck and have to get somebody out to rectify what I might have messed up.
Also, am I correct in assuming that my 1.9 diff is not slip-limited, and therefore requires 75w90 GL4 oil, and not 75w140?
Thanks in advance,

Boosh.
Boosh
Joined: Sun 30 Nov, 2014 22:40
Posts: 324

  Z3 roadster 1.9i

Re: Leaking rear diff

Post by Boosh »

Anyone?
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Southernboy
Joined: Thu 07 Oct, 2010 12:39
Posts: 6436

  Z3 roadster 3.0i
Location: Johannesburg

Re: Leaking rear diff

Post by Southernboy »

Your removal / replacement procedure is correct. Also, the diff is not an LSD unless there is a stamped LS and the number on the diff.
"Normal is overrated"
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Boosh
Joined: Sun 30 Nov, 2014 22:40
Posts: 324

  Z3 roadster 1.9i

Re: Leaking rear diff

Post by Boosh »

Thanks, I wanted to follow the 6P rule (Perfect Planning Prevents Piss-Poor Performance). I'd like to avoid being stuck on the drive with a car that can't move...

Thanks again,

Boosh.
Del
Joined: Sat 19 Nov, 2011 18:35
Posts: 2136

  Z3 roadster 1.9

Re: Leaking rear diff

Post by Del »

GL5 rated gear oil for the diff (GL4 gearbox) - the standard 1.9 diff will hold a fraction under 1 litre (75W-90) so you only need 1 bottle :) I would tend to go for the Castrol/BMW recommendation. :)
Boosh
Joined: Sun 30 Nov, 2014 22:40
Posts: 324

  Z3 roadster 1.9i

Re: Leaking rear diff

Post by Boosh »

Thanks for that.
Just bought a size 14 Allen key and 2l of GL5 oil (didn't have anything smaller). All I need now, is to check whether the rubber hose I have fits on my pump. And nice weather on my next day off. Probably the hardest part...

Boosh.
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