Diff or half-shaft? Opinions please....

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Dr Firefly
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Thu Sep 21, 2006 7:57 pm

Arse.
Just got clutch and cambelt sorted, but now hearing a slight whiney noise from the back. Different noise to when I had a wheel bearing go on me, so I'm thinking either the diff or the uni-joint on a rear half-shaft. Any ideas on how to find out which it is?

Because the clutch was so knackered, it was shaking the drivetrain like hell, and I'm worried that's knackered the diff, there's a bit of play on the input flange now. It's a shame, especially as Stevetigger told me it had only done 75k when he sold me it. Any chance of a diff going that early if it's had regular oil changes? The oil's still really clean in it when I checked - still yellow and fairly clear.

And on a side note, if I need one, has anyone got a 3.91 diff in amazing brand new condition (for less than Ԛ£40 :D)?

But it could also be a uni-joint, as the gaitor on it has been damaged at some point, and there's a line of oil sprayed out over the bottom of the chassis. But it's been like that for ages, and I was just crossing my fingers it would last, as the actual shaft was slightly damage around the seal and even with a new gaitor wouldn't have been right - means a whole new half-shaft.

Any ideas?
SGP
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Thu Sep 21, 2006 9:33 pm

The Diffs often make a "hissing" noise, try driving it with the back seat pulled out and the fuel pump cover removed this way you'll be rable to really hear it properly.I've never heard a cv joint make a whine,in my experience when they are wrecked they make a loud clicking noise (on front wheel drive cars only)
If it ain't broke..
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Chris-W
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Thu Sep 21, 2006 10:00 pm

Quite - failed CV joints sound like a high speed Newton's Cradle.
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Dr Firefly
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Thu Sep 21, 2006 11:24 pm

Ok - well I'll assume the CV joints are ok for now then. Strange that the oil's fine in the diff tho. But it's definitely a hissing sound. Sounds like a load of cogs swishing round in liquid (wonder why that is :) ) Sigh. Well, it's only just audible at the mo - any recommendations on what oil to put in to try and keep it going a bit longer? It's just got normal bog-standard gear oil in at the moment. And it looks like I'm going to be in the market for a new (or at least under 100k) diff from someone doing a 335 or 327 conversion. Anyone got any ideas on who to get in contact with? Cheers, Ian

Oh, and could the fact that it's only a 318 diff on a 320 explain why it's gone so quickly? I wouldn't have thought the power output is that different?
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Treeman612
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Fri Sep 22, 2006 2:24 pm

Hi - had similar problem on my 320i - when cruising 70 ish on light throttle, got a slight whine on throttle lift-off. Disappeared as soon as throttle applied, not audible below 50-ish. Diff oil was clean, very little backlash. Changed to re-con diff off Zoner, done only 12,000 miles. Problem solved. :)
IMO condition of oil, backlash etc does not neccessarily mean diff is ok. relatively small amounts of bearing wear will mean some noise. If it's an open diff, you could try a thicker grade of oil, but this would only disguise the problem. Slick 50 do a diff additive which supposedly 'quietens' noisy diff, but I haven't tried it. Anyone else used this stuff?
SGP
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Fri Sep 22, 2006 7:15 pm

I have not tried the slick 50 in the diff,but have used their engine additive (in a diesel Escort)it did do something all right, but for a noisy diff the only solution is a rebuild or replacement.I had mine reconditioned at quite an expense which did quieten it down, ultimately however I ended up replacing it with a second hand unit which is perfect (thankfully).If it's any consolation,these diffs will quite happily motor on for years while noisy.Andy Everett of "The E30 bible" fame reccomends putting extra carpet under the back seat to reduce sound intrusion into the cabin.Best solution?pick up a known good one from Fab Recycling.
Regards.
If it ain't broke..
Fix it till it is :)
Dr Firefly
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Fri Sep 22, 2006 10:22 pm

In that case - as long as I'm not in imminent danger of having wheels lock up on the motorway at 80, I might leave it for the time being and see if it gets much worse. Fab Recycling? I'll look them up. Cheers everyone for the help.
SGP
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Sun Sep 24, 2006 11:05 pm

Yes, Fab Recycling are the business when it comes to beemer parts.
If it ain't broke..
Fix it till it is :)
Dr Firefly
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Mon Jun 04, 2007 12:28 pm

Just for anyone that this could be useful for, the advice on here was perfect - car's done another 10k miles since then with no problems whatsoever from the diff, and I'm now finding out what a failed CV joint sounds like - lots of clicking! Totally different noise to the hissing noise I was worried about.
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