Rear trailing arm front bushes

[WPR678B]

I noticed that there seemed to be a great deal of "float" in the large front bush in the rear trailing arm on my 145 so i ordered the bushes and set to the arms and changed all the bushes, including the tie rod ones.
I also have that "rocking" feeling when the car and engine are at the same speed, at neutral speed you could say, which i hoped would be cured by the fitment of these new bushes.
Sadly the new one's seem to have as much "float" in them as the one's they replaced!!
Is this a common problem and is there a "fix" out there, different arms maybe?
I would be very grateful of any feedback!

[john h]

Not sure what you mean by 'car and engine at the same speed'. Could you be more specific?

Is the rocking side-to-side? If so, likely to be Panhard rod bushes.

John

[WPR678B]

Originally Posted by john h

Not sure what you mean by 'car and engine at the same speed'. Could you be more specific?

Is the rocking side-to-side? If so, likely to be Panhard rod bushes.

John

What i mean is if you are crusing on a straight flat road, not accellerating or decellerating it feels as if you are "jumping along".
I find myself never going at a constant speed anymore as i'm always speeding up slightly and then slowing slightly to avoid it!
When the car is parked on the level with the handbrake on and you rock it back and forth there is easily 25mm of back and forth movement in the bushes, the same as the one's i took out thinking they were knackered.
I hope this makes sense!?

[john h]

Strange symptoms, and very odd that a new bush would have 25mm play!

Are you sure the play is in the bush itself? Could it be the hole on the that the bolt goes through has worn oval? Or the triangular bracket come loose?

Have you also checked the bushes at the other end of the trailing arm, directly under the axle?

Also, when rocking on the handbrake, the car can move back and forwards due to wear in the brake backing plate allowing the handbrake shoes to rotate slightly.

John

[WPR678B]

Originally Posted by john h

Strange symptoms, and very odd that a new bush would have 25mm play!

Are you sure the play is in the bush itself? Could it be the hole on the that the bolt goes through has worn oval? Or the triangular bracket come loose?

The bushes are new (from Brookhouse Volvo) and the holes are the correct size for the bolts. Nothing is loose, its purely the bush material compressing 1/2" either way when the car is rocked! If you look at the front bush while rocking the car, you can see that the bolt stays secure in the hangar and the whole arm moves back and forth inside the brackets where the rubber material is compressing!

Originally Posted by john h

Have you also checked the bushes at the other end of the trailing arm, directly under the axle?

I also replaced these bushes at the same time (worst part of the job!!)

Originally Posted by john h

Also, when rocking on the handbrake, the car can move back and forwards due to wear in the brake backing plate allowing the handbrake shoes to rotate slightly.

John

I do also have some movement on the handbrake shoes, but very slight and not a cause for concern.
I will try and maybe get a short video of it as they say a picture says a thousand words! Now all i need is some daylight when i'm not at work!! LOL!!

[john h]

You can get bushes that restrict the movement. This post from my thread shows an old (standard) bush and a new powerflex one.

http://www.volvoforums.org.uk/showpo...&postcount=127

However, I don't think your rocking is being caused by bushes. If they are all new, good quality and tight, I think the cause must lie elsewhere.

Does it happen driving at any constant speed, or is it more apparent at slow town speeds, say 10 - 30 mph? If the latter, it could be a tyre on which the inner carcass has broken down. Try swapping each wheel in turn with the spare and test driving. (The torque applied through the tyre when accelerating or braking may distort the tyre enough to mask the effect. At higher speed, the effect can also be masked by centrifgal force in the tyre, or it might feel like a wheel balance problem).

I'm no expert with axles, but I wonder if a bent half-shaft could give this effect at low speed? (At high speed, I guess you would get a vibration and/or droning noise).

Another possibility (again, at low speeds) would be a rear disc that's warped, or not mounted perfectly 'square'. (A warped front disc would give an effect through the steering). Braking might mask the effect, but can't see why accelerating would make any difference to this one.

An interesting problem!

John

[WPR678B]

A short and poor quality video to try and show the excessive movement i am on about!

http://www.youtube.com/watch?v=ePDrqD_4J7g

Hope you can view it ok!

[WPR678B]

Originally Posted by john h

I don't think your rocking is being caused by bushes. If they are all new, good quality and tight, I think the cause must lie elsewhere.

A short video in the link above will hopefully show better what i mean. They are a tight fit in the arm and are Scan-tech items purchased direct from Brookhouse Volvo. It seems the compound is just too soft maybe? The originals that i took out had the same amount of movement, hence me thinking they were shot!

Originally Posted by john h

Does it happen driving at any constant speed, or is it more apparent at slow town speeds, say 10 - 30 mph? If the latter, it could be a tyre on which the inner carcass has broken down. Try swapping each wheel in turn with the spare and test driving. (The torque applied through the tyre when accelerating or braking may distort the tyre enough to mask the effect. At higher speed, the effect can also be masked by centrifgal force in the tyre, or it might feel like a wheel balance problem).

I'm no expert with axles, but I wonder if a bent half-shaft could give this effect at low speed? (At high speed, I guess you would get a vibration and/or droning noise).

Another possibility (again, at low speeds) would be a rear disc that's warped, or not mounted perfectly 'square'. (A warped front disc would give an effect through the steering). Braking might mask the effect, but can't see why accelerating would make any difference to this one.

An interesting problem!

John

It will happen at any constant speed, but the faster the more you notice it i would say. The discs were all skimmed by a local and trusted engineering shop when i rebuilt the brakes so i would rule them out.
The tyres were also all brand new less than 4000 miles ago and as i said previously, its only when the car and engine are at a "matched" speed. At all other times it is smooth and without any jerkyness (if that is a real word!).
I am personally convinced that these bushes are where the problem lies and was wondering if anyone else had encountered the same.

[john h]

There does seem to be a lot of movement. I wonder if the bush is fitted correctly? I suspect that the cut-out section should be top & bottom, not front and back?

Even if the the bush is too soft, I am struggling to imagine what, specifically, could make it cause the effect you describe. Driving at a steady speed, there is very little force acting upon that bush. There's enough engine torque to offset the aerodynamic drag, but the torque reaction on the front bushes is not large (because of the length of the trailing arm), plus it is a constant, steady force, not something that would tend to start a rocking movement.

Try driving along and, when the rocking effect is happening, dip the clutch.

If it carries on rocking when coasting, then I can't see how the bush is the cause because there is virtually no forces acting on it when coasting.

If the rocking stops immediately, then it is related to engine torque. I would check the engine mounts... perhaps some wierd 'resonance' between soft/broken engine mounts and the rear bushes? Although I'm doubting that, to be honest!

John

[WPR678B]

Originally Posted by john h

There does seem to be a lot of movement. I wonder if the bush is fitted correctly? I suspect that the cut-out section should be top & bottom, not front and back?

They were fitted the way they are now before i removed them and both the "green" Volvo workshop manual and the Haynes both say that the cutout should be 90 degree's to the arm, which is how they are fitted.
Are the Superflex bushes you have used round or do they still have the cut out?
I will try the clutch dipping which i suspect will stop it straight away in the same way that slightly slowing or speeding up does.
Don't get me wrong, the car is not "lurching" along when it does it, but it is noticable but then i am used to Morris Minor commercial suspension which has as much give as a go-cart!
I was planning on replacing the engine and gearbox mountings when i fit the overdrive, but i may fit the engine mounts a bit sooner!
Any advice on these as i'm sure i've read somewhere on here there is a certain brand to avoid!