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[doz]

I've still got a transmission vibration which is making the car almost undriveable. I'm running out of ideas. I've changed the wheels,rear discs,rear drive shafts. So I can only see me having 3 options left. Diff, prop shaft or gearbox. Diff is an X ros LSD. It works well and is still actually working as an LSD. So my symptoms are at 56 MPH There a very abrupt vibration which is bad enough to wobble the gearstick (auto) sun visors and even the front passenger seat. Can be felt through the floor of the car, it's almost a thud,thud,thud but softer. Is there anything in the diff which could go out of balance enough to cause this? I can't for the life of me think what would. The vibration feels to slow to be the prop. I've checked all the flange couplings and all are ok. I'm running out of time as well. I fear I'm going to have to buy another car and break this one for spares to recoup my LPG conversion costs. Oh and there's no wheel wobble etc and all wheels are now round!!!!!

[terry paget]

Is the prop shaft central bearing rubber support OK? They thump when they feel like it and the rubber is torn.

[2woody]

I had just that from a pair of knackered front wishbone bushes.

[doz]

Will double check the prop bearing but I have given the prop a good going over. Can you explain more about the wishbones? My problem is very speed specific. It's not related to road surfaces or engine load. In fact I can replicate it in any gear as long as I'm doing 56 MPH. It seems to build with speed from say 40, peek at 56 and is gone by 70. I really am at a loss.

[05omegav6]

Have the wheels been rebalanced

[VXL V6]

Probably not relevant but I have a cabin vibration / gear stick vibration on my 2.6 which I know is down to an oval rear wheel.

The wheel used to be on the front of my diesel and gave out of balance symptoms.

Really must get one of my spare sets of wheels refurbished and some tyres sorted.

[doz]

Tried different wheels  Even had 2 new tyres fitted and had a repair done to a rim as it had a flat on the inside rim

[Entwood]

Daft idea number 4000 and odd .......

Is it worth trying to get it either on a rolling road, or to jack the back end up, then jack the wheels to level, and run it "off the ground" That was how I found that my noises were Diff and not bearings .....

That way you can investigate whilst the drive train is in motion but the car is not .. if that makes sense ........

[doz]

Yea, I've been thinking that I'm just not brave enough to stick me head under a car doing 56 mph on axle stands 

[Kevin Wood]

It'll be something at wheel rotation rate at that speed. Gearbox output will be 2-3000 RPM at that speed - too fast for such a vibration, so that narrows it down to wheels, tyres and driveshafts. Are you sure you haven't got a bulge in a tyre? Also, as said, any failed bushes will make any inevitable slight imbalance in the wheels many times worse.

[chrisgixer]

Could the dif be slipping?

Or another way of putting it, is the vibration the same as when the dif slips when turning. (As mine does)

Although, I'm struggling to see why the dif would slip when driving straight ahead, unless there's an odd sized wheel, or maybe something severly dragging on one side.


Actually that seems unliky tbh, although seemingly running out of ideas maybe...?





... Failed shock? No damping can see a slightly out of balance wheel banging up and down like a good one. You may have seen it in other cars on motorways? Vans mostly, especially if the bad shock is unloaded on the inside of a turn, on a slip road say.

[chrisgixer]

Has it got poly rear donuts, and as this sounds a long term issue, did it get better or worse when poly fitted... If the issue was there prior to of course.


I presume there is no sensation of this through the steering wheel itself. Or at least only residual vibration from surrounding components...?

[chrisgixer]

Although....

Getting a bit imaginative now it must be said...

Is the car well set up geometrically ? Just wondering if the set up could be out enough for the rear axle to be pushing the car out of straight, so that as far as the dif is concerned its constantly cornering. Although I guess the slip would have to be set exceptionally tight and the set up to be way out for this to happen...

...so much so that I doubt its possible tbh. At the risk of getting way "outside the box" but just trying to think the dif idea through.

If wheels, drive shafts and discs have been changed, what's left? Brake calipers, hand brake set up, suspension, dif, prop shaft, bushes. ...?

[2woody]

Will double check the prop bearing but I have given the prop a good going over. Can you explain more about the wishbones? My problem is very speed specific. It's not related to road surfaces or engine load. In fact I can replicate it in any gear as long as I'm doing 56 MPH. It seems to build with speed from say 40, peek at 56 and is gone by 70. I really am at a loss.

that's exactly what it was.

No vibration up to 50.

Felt like the entire front end was coming off from 50 to 70

Fine from there on up.

vibration strong enough to make you lose focus

[chrisgixer]

I've had that flapping wheels vibration from failed front bushes, and found the vast majority if the vibration was felt through the steering wheel, in a left right left tight left right manor in very quick succession, in my case.

Ime the steering is quite insulated from the rest of the car, so a fault there is felt through the steering wheel, a fault elsewhere is felt everywhere else except.... Or at least its the the last place affected if it is indeed a fault at the rear of the car. Ime.