Diff whine is common on the Omega and difficult to 'place'. The noise is generated at the contact frequency of the crownwheel and pinion teeth and is most noticable on the overrun at any speed, although it may also be noticable at 55-65mph cruising.
I have rebuilt one of these diffs and they are very difficult. You must use 'engineers blue' to set the pinion teeth contact pattern (adjustable via spacer washers and a crush collar) and backlash (about 7 thou IIRC). DIY job with new bearing kit etc. is about £100 in parts. Exchange unit will probably set you back at least £400 (from an independent rebuilder)
Make sure diff oil level is correct.
A good rebuilder (does mail order exchange units) is Nicol Transmissions, Kidderminster. Speak to the owner, Nick Bevin. He does rebuilds for fleet customers (eg AA) and has a very good reputation without being OTT price wise.
Omegas are such troublesome cars, esp. V6, I wonder why people persist in buying them.
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PS - when diff gets quite worn you can 'play' this noise on the throttle - i.e. as you ease on and off throttle the noise will come and go. HTH.
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Thanks Aprilia.
Good luck Smokie.
I think I can probably leave mine for now until it all becomes more noticable.
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For what it's worth, Goodyears. I suspect Aprilia has the real cause.
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Thanks all
I'm not handy enough to carry out this kind of work myself - often wish I was.
Jon, the tyres were Avons - maybe that's the cause, but I doubt it. Although when I bought the car the fitted tyres gave horrendous tramlining, which was cured with the next set I bought.
At present the noise really isn't THAT bad - I really only noticed it last weekend when driving some considerable miles with no ICE on.
So unless anyone suggest to the contrary, I am going to do the same as Scotty - wait until it becomes more intrusive (and probably easier to diagnose!)
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Re cost of new diff, Vx only want c£2,500 for a complete unit!!!! I got a really good one of the net for £150.
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Just a brief update now that I've spent nearly £900 tracking this noise down...and hopefully curing it
Mech thought it was os wheel bearing, changed it, no change
So used old (good) o/s wheel bearing on n/s - no change
Changed front pads & discs - no change
Swapped wheels front to back - no change
Due to uneven tyre wear on n/s front, went to Micheldever today for tracking and two front tyres.
Tracking was spot on.
All 4 Avon tyres were "out of shape" and badly stepped (although not yet illegal)
New tyres *seems* to have cured the problem. Goodyears, £99 per corner.
Tyre mech said I should never have used Avons...
But then he would!!
Anyway, top marks to JonM for identifying this accurately at the top of this post!
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I have come across cars where the tyres are making a noise, but I've found that weather makes quite a difference (i.e wet or dry road) because of the lubricating effect of the rainwater; whereas with a 'mechanical' noise it tends not to alter with the weather.
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Out of interest which Avons were they, and what Goodyears did you replace them with, I had problems with my Omega when I have Goodyear Eagle F1s on the front, it would tramline and chase the camber of the road, going back to more of a 'comfort/grand touring tyre' cured the problem.
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The Avons were ZZ somethings I think. The Goodyears are Eagle F1s.
I bought the car with original tyres (can't remember if Pirelli or Michelin) and it tramlined awfully.
Swapped them for B F Goodrich which hardly tramlined at all, and were good, grippy and reasonably priced.
Then the Avons, now the Goodyears.
IIRC you can get camber/toe in adjusted to reduce the tramlining effect - not sure where I read it, probably here somewhere. Da man at Micheldever deliberately offset (?) mine yesterday to help it out.
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Well, you have the best tyres for grip, that's for sure, I hope you have no tramlining, I also think the F1s are smooth and quiet too, compared to the Pirelli P6000 Js I replaced them with! I still keep F1s on the rear, hate mixing them on a car, but they are so grippy in the wet, it defies belief!
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I too had problems with Avon ZZ1's on the Omega and also thought it was the diff when I first heard it. Astonishing what difference switching to Conti Premium Contacts has made, only wish I had done it earlier.
With regard to the vibration on braking (assuming it is an auto, can you feel it through the gear selector too?). Mine also does it. I have it on good authority that this is most likely to be failed lower suspension arm bushes. The most common one to fail is the large rubber bush with the bolt going vertically through it. When this fails it often causes the inner edge of the tyres to wear as they toe out at speed. It may not show up when the tracking is checked as the bush returns to normal when the car is not moving. If the front of the car is jacked up the rubber centre of the bush can be seen to have torn away from the metal surround.
In the case of the vibration however I am told this due to the front bush on the suspension arm, which the bolt goes through horizontally. The experts say it is better to have the whole arm (complete with new bushes) replaced but this is not cheap. They also suggest doing both arms (all four bushes) at the same time then getting a full geometry check and adjust (castor, camber and toe) not just the tracking as done at most tyre centres.
This is the next job to attend to for me, will report back if it is a success.
Jon L (not the same one as higher up the thread)
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Jon
You are spot on i too have a 2.5 Omega had the same problem but with michelins tramlining and sounding like bearings gone my garage said lower bushes had these change no difference i was then told i was silly just changing bushes i should have changed the whole rms this i did £75 each from Andrew Pages no different suspect bearings changed these no different. On my other cars i have always had Avon so i wrote to avon and they said there was a problem with zz1 but the new zz3 was better and told me to increase the toe in. I fitted the tyres and it made no diference to the tramlining but the noise went. I was on holiday a couple of weeks later and got talking to a chap who was a mechanic for the police force and when i told him i had omega with probs he gave a wry smile and said the answer is to increase toe from 0.10 to 0.20 in millimetere is 7mm toe in this i did and voilla car runs absolutely perfect i wish i had took his address so i could thank him propely he talked of putting protractor on a straight pencil line to work it out in miilmetres as not many garages have equipment that toes in degrees
Robert H
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I'm not technical, but I had a look at these bushes when the car was up in the air. They looked OK to me. The new discs and poads seem to have cured the small judder when braking (for now anyway!).
There is a Vauxhall owners cluib on Yahoo which I subscribe to where someone has posted the following:
Auto Parts Online are selling wishbones at £26.00 each.
sslrelay.com/buypartsby.co.uk/wishbonelh_details.p...0
Whether those are the parts you need I'm not sure, but they look cheaper tham you mention. Also www.autovox.com had the same parts at £45 each IIRC. Hope that helps!
(NB there was once discussion either here or there, can't recall which, that the cheap parts do not use good rubber in the bushes...)
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Said I would report back when I had done the front bushes.
Well it has cured the vibration completely. These bushes, unlike the verical ones, were apparently a nightmare to remove(needed drilling and hacksawing)cost me an extra £10 each to remove and replace.
On reflection I think replacing the whole arm is the best policy. Lets face it if one of the three anchoring points has failed the chances are the others will soon need replacing and if you do both bushes and the ball joint you might as well do the whole arm, especially as the ball joint has to be drilled off!
If you have a friend in the trade Vx part is about £45 each apparently, The bushes have been modified somewhat because of the failure rate I suspect, so would not recommend non Vx.
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I was going to get the arms done in their entirety, it was the next step after the tyres. Yep, £45 from the trade catalogue, also from AutoVaux I think.
When I had the wheel bearings done I could have just got the bearings, or the bearings with hub. Price differential was quite large but my mech said he'd go for the full assembly as it can sometimes be impossible to break them apart.
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