Omega Owners Forum

Omega Help Area => Omega General Help => Topic started by: Jan Suhr on 08 November 2018, 16:00:16

Title: Vibration in rear when turning
Post by: Jan Suhr on 08 November 2018, 16:00:16
I have a problem on my winter car. When turning under power it vibrates and sounds. Worst when starting from standing still and turning around a street corner. Most when turning right and there as well going left but not as much. It seems like it looks up briefly on and off

Brakes are OK

Doing a right turn on idle and not under power no noise or vibration it is only under load.

Nothing when going straight ahead.

So what could it be?

If it is the diff wouldn't give noise in all situations?

Could it be the driveshafts?

There is no common wheel bearing sound and driving at speed straight ahead it is quiet.


Appreciate any advise


Thank
Title: Re: Vibration in rear when turning
Post by: Doctor Gollum on 08 November 2018, 16:39:29
What condition are the tyres and road surface?

Does the TC light flash?
Title: Re: Vibration in rear when turning
Post by: Jan Suhr on 08 November 2018, 16:58:29
Tires are fresh and didn't make any sound on the car I had them on before.

No TC light
Title: Re: Vibration in rear when turning
Post by: Jan Suhr on 08 November 2018, 16:59:24
And the tires don't make any sound when driving straight on the road, eve up to 70mph speed
Title: Re: Vibration in rear when turning
Post by: Kevin Wood on 08 November 2018, 17:31:05
Does it have a limited slip diff? Just thinking that they are probably more common in your part of the world?

They tend to groan a bit when turning.
Title: Re: Vibration in rear when turning
Post by: Doctor Gollum on 08 November 2018, 17:50:37
Did you spin the wheels?

Switch the TC off/sports mode on and see if it repeats :y
Title: Re: Vibration in rear when turning
Post by: polilara on 08 November 2018, 18:20:58
Does it have a limited slip diff? Just thinking that they are probably more common in your part of the world?

They tend to groan a bit when turning.

I have (Finland) limited slip diff, it really make that sound as described by Jan Suhr.
Title: Re: Vibration in rear when turning
Post by: Jan Suhr on 08 November 2018, 18:24:48
Well it is not just a sound it is kind of heavy vibrations too. Turning on gravel the tire sort of drags and the release a short moment before dragging again.

I haven't checked yet but I believe cars sold in Sweden cam with the limited slip differential.



Title: Re: Vibration in rear when turning
Post by: Doctor Gollum on 08 November 2018, 18:55:35
It could also be the traction control doing its thing as that will brake the spinning wheel, usually the inside one as you turn :y
Title: Re: Vibration in rear when turning
Post by: Jan Suhr on 08 November 2018, 19:01:08
It could also be the traction control doing its thing as that will brake the spinning wheel, usually the inside one as you turn :y


I just came back from a little test run on a gravel road.

With TC turned off it spins both wheels, so we can say that it has a limited slip diff.

The situation with the vibration is the same with TC on or off.

What confuses me is that there is no vibration when the car just roll around a corner. It only vibrates under power.

It sounds like it could be the diff but wouldn't it also vibrates when no power is applied?


Title: Re: Vibration in rear when turning
Post by: MonzaGSE on 08 November 2018, 19:32:05
Have the exact same as you described om both my 86 Monza and the 95 Omega mv6. Typically when you accelerate from a standstill around a corner. I always thought it was the lsd working. Had both cars for years and they dont seem to get any worse.
Title: Re: Vibration in rear when turning
Post by: Andy H on 08 November 2018, 19:33:22
Have you checked the condition of the rubber bushes on the differential and the subframe?

Is it possible that you are getting metal to metal contact due to excessive movement in a worn rubber mount?
Title: Re: Vibration in rear when turning
Post by: Kevin Wood on 08 November 2018, 19:42:06
Might also be worth replacing the oil in the diff if it is a LSD.
Be sure to use a mineral oil with the GM LSD additive.
Title: Re: Vibration in rear when turning
Post by: Jan Suhr on 08 November 2018, 19:45:03
Might also be worth replacing the oil in the diff if it is a LSD.
Be sure to use a mineral oil with the GM LSD additive.

Yes I have been thinking about it and I'll do it soon.
Title: Re: Vibration in rear when turning
Post by: LC0112G on 08 November 2018, 22:08:11
Might also be worth replacing the oil in the diff if it is a LSD.
Be sure to use a mineral oil with the GM LSD additive.

^^^ This ^^^

And you MUST use the additive. The additive is a friction modifier which allows the diff plates to slide smoothly over each other. If you don't use the additive the plates release and grab suddenly, which isn't good for any of the LSD gubbins. It causes the plates to get very hot and wear rapidly, and ultimately this wrecks the LSD.
Title: Re: Vibration in rear when turning
Post by: Jan Suhr on 08 November 2018, 22:20:49
Might also be worth replacing the oil in the diff if it is a LSD.
Be sure to use a mineral oil with the GM LSD additive.

^^^ This ^^^

And you MUST use the additive. The additive is a friction modifier which allows the diff plates to slide smoothly over each other. If you don't use the additive the plates release and grab suddenly, which isn't good for any of the LSD gubbins. It causes the plates to get very hot and wear rapidly, and ultimately this wrecks the LSD.

Yes I know about the additive and its importance. Been a GM-guy for over 40 years and on the US Muscle cars that additive were very important too.

There is no problem to get it here in Sweden too since we have a lot of old American muscle cars over here.

Some of the rear end oils already have the additive mixed in the bottle.


Thanks
Title: Re: Vibration in rear when turning
Post by: Jan Suhr on 09 November 2018, 11:10:34
I had recently the rear end lowered when I put in new springs and shocks. The rubbers that I saw wasn't damaged.

Title: Re: Vibration in rear when turning
Post by: Jan Suhr on 11 November 2018, 13:27:23
Ok I have now changed the oil in the diff.

The old oil didn't look bad or smelled more that they usually do.

I still get the vibration when turning but I think it is a little better than before. I have driven it around the blocks for a few kilometers to get the oil working.

At least I now know that I have oil in it  :)


If it doesn't get any better I guess I have to find a replacement.
Title: Re: Vibration in rear when turning
Post by: 0795omega on 11 November 2018, 21:05:38
could allways just live with it mine does this allso!
Title: Re: Vibration in rear when turning
Post by: polilara on 12 November 2018, 07:44:04
could allways just live with it mine does this allso!

Yes, as mine, but do you have it like Jan Suhr informed: "there is no vibration when the car just roll around a corner. It only vibrates under power"??

I cannot test it now as I am changing springs, shocks, wishbones etc, but I will do it when ready.
Title: Re: Vibration in rear when turning
Post by: LC0112G on 12 November 2018, 11:12:14
My understanding is that once the LSD plates are damaged they are basically scrap, and there isn't much you can do to fix them except replace.

The LSD plates can warp or become pitted. Warping happens when the oil gets too hot. Pitting is caused by micro welding where the heat of the slipping diff causes the plates to instantaneously weld together and then break free again. This roughens the surface and causes more heat/micro welding/pitting. Ultimatley it's down to the oil breaking down or no/insufficient friction modifier.

Replacing the oil can help quieten things down again for a while, but it can't fix any warping or pitting.

It's also possible that one of the bearings inside the diff is damaged, but you'd expect that to show up when driving/accelerating/overrunning straight and level too.
Title: Re: Vibration in rear when turning
Post by: Jan Suhr on 12 November 2018, 11:23:07
My understanding is that once the LSD plates are damaged they are basically scrap, and there isn't much you can do to fix them except replace.

The LSD plates can warp or become pitted. Warping happens when the oil gets too hot. Pitting is caused by micro welding where the heat of the slipping diff causes the plates to instantaneously weld together and then break free again. This roughens the surface and causes more heat/micro welding/pitting. Ultimatley it's down to the oil breaking down or no/insufficient friction modifier.

Replacing the oil can help quieten things down again for a while, but it can't fix any warping or pitting.

It's also possible that one of the bearings inside the diff is damaged, but you'd expect that to show up when driving/accelerating/overrunning straight and level too.

Well that explains it in my case and what I suspected. The former owner was a young guy who did some burnouts with it. A lot of rubber in the rear wheel houses.

The car is in very good shape besides this, a few minor things still to fix. I will start to look for another diff.

Thanks
Title: Re: Vibration in rear when turning
Post by: Jan Suhr on 12 November 2018, 11:36:43
A question regarding this.

Is there a difference in gears between manual or automatic transmissions.

I see that for 2.5 or 2.6 litre cars there are three different gears, 3.70, 3.80 or 4.22

I have found a couple of them on Swedish scrap yards but they are all from manual cars.
The lists also show that the 2.2 litre has the same gears.

Edit: I found on https://www.opel-infos.de/modelle/omega_b2.html that the 2.2 and 2.6 with automatic trans has the same gearing at 4.22. There are a few of them available here.



Thanks
Title: Re: Vibration in rear when turning
Post by: LC0112G on 12 November 2018, 11:58:59
If you open up the diff you'll find it's basically 3 parts -

1) the input drive pinion (leave this alone)
2) the crown wheel
3) the "centre"

The crown wheel bolts to the centre, whilst the centre contains all the LSD gubbins. So....

If you get a good LSD from a scrappy but the gear ratio is wrong, then you can just open up your existing diff, whip out the centre+crown wheel, swap the crown wheel onto the centre from the good diff, and re-assemble. This means you're using your old pinion and crown wheel (so the gear ratio is the same) but a new LSD centre.

Obviously there is a bit more to it than that, and you must ensure the backlash and side bearing preloads are correct on re-assembly.

Disclaimer - I've not done an Omega diff but I am in the middle of doing a Lotus Carlton one (which uses cones not plates) so the internals are similar. Hopefully it'll be going on the car this weekend.

https://www.aussiev8.com.au/driveline-suspension/71923-btr-m78-diff-question.html
Title: Re: Vibration in rear when turning
Post by: Kevin Wood on 12 November 2018, 12:51:02
https://www.aussiev8.com.au/driveline-suspension/71923-btr-m78-diff-question.html

Someone's been busy. :y
Title: Re: Vibration in rear when turning
Post by: Doctor Gollum on 12 November 2018, 20:18:13
A question regarding this.

Is there a difference in gears between manual or automatic transmissions.

I see that for 2.5 or 2.6 litre cars there are three different gears, 3.70, 3.80 or 4.22

I have found a couple of them on Swedish scrap yards but they are all from manual cars.
The lists also show that the 2.2 litre has the same gears.

Edit: I found on https://www.opel-infos.de/modelle/omega_b2.html that the 2.2 and 2.6 with automatic trans has the same gearing at 4.22. There are a few of them available here.



Thanks
3.2 auto should have a 3.9 diff ;)
Title: Re: Vibration in rear when turning
Post by: Jan Suhr on 12 November 2018, 20:30:57
A question regarding this.

Is there a difference in gears between manual or automatic transmissions.

I see that for 2.5 or 2.6 litre cars there are three different gears, 3.70, 3.80 or 4.22

I have found a couple of them on Swedish scrap yards but they are all from manual cars.
The lists also show that the 2.2 litre has the same gears.

Edit: I found on https://www.opel-infos.de/modelle/omega_b2.html that the 2.2 and 2.6 with automatic trans has the same gearing at 4.22. There are a few of them available here.



Thanks
3.2 auto should have a 3.9 diff ;)

Yes I saw that I had edited the wrong value after I had edit and it wasn't possible to edit again :-(