Sporadic Vibration through chassis and steering wheel

[bad devotions]

Hi all,

It's been a while since my last post, but i am hoping you can help me work out what to do/check next.

I experience vibration either through the steering wheel or through the chassis or both from any speed above 60mph. It doesn't persist at any speed. E.g. i could be doing ~70mph and the car will be fine, then all of a sudden i'll get the vibration, then it'll go away. but it's happening more often than not and on occasion it's very noticeable. I've tried to detect a pattern but nothing that i can work out is making the vibration happen.

I've already checked and balanced the wheels and made sure front and rear are aligned. Whilst the garage was doing the work I asked them to check for play in the track rod ends and also to check the tyres for eggs or signs of failure. All of which are fine.

The only handling mod i have done is put a super-pro ALK on.

So.... what do i check next? suspension seems ok, but could it be a cracked spring? Is it a problem with the ALK? is it possible to install these incorrectly? Could it be an aero thing? maybe some of the undertray is causing the vibrations??

it's doing my head in so any recommendations would be useful 

[Dan_FR]

When does it happen?

• Cruising at a steady speed i.e. Cruise control on
• Gentle acceleration
• Heavy acceleration i.e. loading car up in high gear)
• Transition from acceleration/cruise to deceleration/engine braking
• Deceleration/engine braking

Is it definitely wheel/suspension related or could it be engine/gearbox? i.e. an engine misfire, odd/rough running due to some other fault, a worn DMF, gearbox/Differential issue etc.

[bad devotions]

hi dan,

i can't detect a pattern. I drove for three and a half hours last night. cruising straight will sometimes do it sometimes not. When i take a bend a load up one side, it subsides, but not always. If i accelerate hard or slowly it makes no odds either. It just starts to happen at around 60mph+.

It feels like something is loose somewhere. Could it be a bump stop? could it be that when the ALK was installed one of the bolts wasn't put on properly? or it was put on the wrong way round? I don't think it's engine related. Not sure what a DMF is to be fair so can't comment on that.

I've read that if you can feel it in the chassis (i.e. through the seat) then it's likely to be a problem at the rear.  TBH i think it's the ALK that's at fault. I rarely do motorway driving so haven't really noticed the problem before, but pretty sure it didn't exist before I had it installed. But if it is at fault i have no clue why.

[pudding]

You drove for 3.5 hours and you couldn't determine what rpm it happens at, or whether it's on over-run, or on the throttle???!

Are you sure it's a vibration and not a wobble?  Steering wheel shake is suspension / wheels.  Vibration is drivetrain.  Worn mounts, worn CV joints, knackered or bent driveshaft...that kind of thing.

A thrumming noise at specific speed is wheel bearings or saw toothing rear tyres.

[bad devotions]

You drove for 3.5 hours and you couldn't determine what rpm it happens at, or whether it's on over-run, or on the throttle???!

Are you sure it's a vibration and not a wobble?  Steering wheel shake is suspension / wheels.  Vibration is drivetrain.  Worn mounts, worn CV joints, knackered or bent driveshaft...that kind of thing.

A thrumming noise at specific speed is wheel bearings or saw toothing rear tyres.

I know right? i was trying all sorts. Doesn't matter what RPM the engine is in, it's just the minute i go above 60 i start to notice it. The faster i go the worse it can get. Driving straight will sometimes vibrate and sometimes not. More often it will. Driving through bends, where the wheels are loaded, reduces the issue, but then when i go back to straight it either re-appears or goes away.

Maybe it is a wobble that is causing the vibration. I get both steering wheel and vibration through the chassis. I can feel it in my bum and also through my left foot whilst at rest to the side of the clutch pedal.

[pudding]

I would say it's probably chassis related then if it's speed specific, and I'm leaning on warped brake discs.   Easily mistaken for tyres out of balance.  A slight warp can cause a shake at speed, but not warped bad enough to cause the brake pedal to pulse at slower speeds.  That is where i'd look first!

[bad devotions]

I would say it's probably chassis related then if it's speed specific, and I'm leaning on warped brake discs.   Easily mistaken for tyres out of balance.  A slight warp can cause a shake at speed, but not warped bad enough to cause the brake pedal to pulse at slower speeds.  That is where i'd look first!

maybe - although not convinced on that as it's not constant. it's intermittent.

The car needs a service anyway so i'll ask them to check when it goes in.

thanks for the suggestions so far though 

[bad devotions]

Day before yesterday i had my return leg up the m40 / m6 back home. 4 hours of driving and still no way of identifying any kind of pattern. sometimes the shaking would be there, other times not.

Anyway, took it back to the garage that did the alignment and wheel balancing and got it up on the ramp. Wheel bearings seem to be fine. Front tyres were fine. no play in control arm bushes. no cracked springs. The rear tyres were worn un even and out of shape so we replaced them. Took it for a quick spin and still the same. I think it may have resolved any shaking through the wheel at 50ish, but up to motorway speeds and it returns (then goes away / then comes back... repeat).

FWIW the front disks were replaced somewhat recently. I had managed to warp them with some enthusiastic driving in the lakes once upon a time and therefore had to replace them. oops. Is there a way to check these at home?

I think i am going to have to drop it into VW to see if they can work it out because i am beat on this :S 

[AJP]

If you get the wobble on throttle as well as braking, I'd say it's unlikely to be just the discs. You might have warped discs on top of another issue - so in fact two different causes causing symptoms that are sporadic and hard to determine.

One thing worth noting, when I got a couple of new tyres on the front they balanced the wheels as expected, but straight away I was getting that tell tale wobble at motorway speed. I took the car to a different place that I use for alignment etc, and they rebalanced the wheels. Problem solved. The main man there explained that not all wheel balancing machines are equal. Some are much less accurate than others. So it might be worth seeking out a place with different/better kit.

[bad devotions]

yeah i was thinking maybe it's more than one issue piled on top of another. TBF i rarely do motorway driving so this may have been an issue for a while that i hadn't noticed. I really don't think it's disks. it doesn't come up on braking its speed related and i can't drive through it if that makes sense. the wobble starts at lower speeds and gets worse the faster i go.

Noted about the balancing and . I'll try a VW garage next and see if they can pinpoint the issue.  It's due a service anyway.

[Ripstop]

One other area to consider is the protective plastic subframe air deflectors. I often see them bouncing around on cars when I follow some. They can start a flutter at certain speeds and cause a standing vibration wave through the chassis and steering. Its also dependent on wind direction as well, sounds silly but they can move quite a lot.  Incorrect tyre pressures maybe?The other would have been wheels need balancing. Other than that ... I don't know.

[pudding]

I'm still leaning on warped discs and/or worn front dampers.   These things tend to have specific resonant frequencies (just like wheels out of balance) which annoyingly always occur when cruising at the national speed limits!

You can check them with a magnetic dial gauge for run out.  You can get cheap but accurate (enough) ones from Amazon.....or for the cost of a set of standard discs, throw a new pair on and make sure the hub faces are spotlessly clean and flat.

[Ripstop]

Just to add to pudding's comment... I had a wobble somewhere that caused the passenger front seat to vibrate at certain speeds. Some days it would be bad and others it would be tiny. I have noticed that after replacing the dampers with new B4's its almost gone. I also think tyre pressure/wheel balance and temperature causes the tiny wobble I have now but the old dampers exacerbated the previous larger wobble. So following on from that it still looks like it could point to a wheel suspension anomaly.