Vibration

[Ivaan]

My car has a vibration similar to that of a wheel out of balance. It comes on at around 70mph. It's of a similar frequency, but not as strong amplitude. It's not wheel balance as I've recently had them checked.

I think it comes from the rear, as it doesn't effect the steering wheel.

It's a Ital live axle, so I'm wondering if it could be a bent half shaft? There's no run out on the wheels, but if I hold the wheel at 9 - 3, there's play in the bearing. There's no movement 12 - 6. The play is only a mm or so, but it's enough to produce a slight clonk.It's the same on both sides. Don't know if it's related to the vibration.

It's a TRT prop with a flexible centre bearing in the tunnel approx level with the driver's knees.The  UJs are in good condition and it's all marked to keep the same alignment when the engine is removed / replaced.

The vibration has been there for quite a while ( a couple of years ), but it's only noticeable on flat A roads. On winding B roads it's no problem, but I'd like to trace and cure it.

Open to any suggestion you may have. Is there an easy way to trace a cause of vibration?

Thanks in advance.

Clive

[elie boone]

Are the A frame bushes in good condition ? if it's a bearing then it should show play in all planes, are the bolts on brake back plate tight ?

[Ivaan]

Hi Elie,

 

I've regularly replaced the bushes below the axle diff, but never the chassis end. Do they wear much?

 

I'll get under and see if there's any movement there.

 

I agree with you about the bearing play, the movements definitely only in the front - back plane, so probably not bearings. You've got me wondering if it's something to do with the disc conversion. Perhaps the backplate or the disc/ hub not sitting quiet right. I'll dismantle and check.

 

Have you had a bent halfshaft? I believe you've done the Rakeway conversion. Might be time to shell out?

 

Thanks,

 

Clive.

[elie boone]

Ivaan, Yes I have done the Rakeway conversion recently, if you are thinking of doing the conversion ask Rakeway to mount the wheel studs. I have seen 2 axle breakages on the same 7 ( track used ) but I think that this is more to do with the 1970's quality of the half shafts.

[John Vine]

An off-the-wall thought...

Could one or both rear tyres be out of round?  What happens if you swap front and rear wheels?

JV

[Ivaan]

Hi John,

I've carefully inspected the wheels / tyres and recently had the balancing checked, so I don't believe it's that.

I need to dismantle the hubs to see if the discs are flat and true against the hubs as they sit between the hub and the wheel. I also need to check the A frame bushes where it meets the chassis.

It's just a question of checking and eliminating the possible causes.

Elie, I assume the studs are a bugger to fit into the hub then?

Cheers,

Clive

 

[elie boone]

Ivaan, not really but the material of the flange ( too soft IMHO ) was pushed out round the stud making a correct fit of the drum impossible.

[Ivaan]

I've had the rear wheels off this afternoon and found the problem.

The drivers side half shaft is floating in / out of the axle, only held in place by the disc and calliper. This also explains the wear on the outside of the disc. When going around a right hand bend, the wheel is pulled towards the outside of the car, with the disc then pressing against the outside brake pad. Must have been like this for some time!

Am I right in thinking that the best fix is the Rakeway conversion?

 

Clive

[elie boone]

You could shim the half shaft to prevent it sliding on the bearing. You do need a pulley for the hub and normally a press for the bearing but as your half shaft is sliding on the bearing I suppose it will come off easily. Then you will have to see of the half shaft is still ok and if the bearing is still ok.

[Ivaan]

Hi Elie,

It's been shimmed before by Road and Race back in 2005 for Ferrino. I still have the receipt.

How much was the Rakeway kit? I understand there could be some knocking about from the Graduates bulk buy a few years ago?

Regard,

Clive

[elie boone]

Unless your bearing is knackered the half shaft shouldn't be moving if it has been shimmed, the raceway kit is about 885+vat

[CharlesElliott]

We haven’t had any issues in Graduates since we mandated the Rakeway conversion. 

[Ivaan]

Thanks.

It's a call to Redline to get new bearings for a temp repair ( I know someone who can tack the bearing and make new shims if necessary ).

Then it's a case of waiting for Santa!

Clive 

[elie boone]

Never tack the bearing onto the half shaft !!!!!!!!!!!!!!!!!!!!

[Ivaan]

[Ivaan]

I need a bit more advice.

I've dismantled the hub and pulled out the half-shaft. The bearing is loose on the shaft, and will side up / down a couple of mm or so.

 

 

 

I'll need a puller to get the hub off off the shaft, to fit the new bearing. ( I can bporrow one from work ) I assume the shims then fill the gap between the hub and the bearing, though I can't see them at this stage.

I can't understand why the bearing is able to move? Do the shims wear?

From what I can glean, Tony Ivatec ( Ferrino ) had new bearings pressed on the shaft and shims made by McMillan back in 2005.

What's the best way of checking the shaft itself is okay and not bent? Is it a simply a question of rolling it on a flat surface?

Thanks,

Clive.

 

 

 

[elie boone]

You have a pm as I can't see the pictures. to check the half shaft you need a lathe. In those 12 years someone might pulled the half shaft out disassembled and the reassembled without shim ?

[Ivaan]

Hi Elie,

 

Bugger! Photo's appeared fine on my machine at home! Now not visible.

 

I've got your Blatmail, so I'll send over the photos later tonight.

 

Thanks,

 

Clive.