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[SMD]

 

Car used to rumble/vibrate at 40-50mph when lifting off the throttle but now it is constantly there between 20-50mph and there is a steering wheel wobble when braking from high(ish) speed, discs are 6 month old GM with OE pads. It needs wishbones and tyres, will get round to doing those when the poly doughnuts arrive. In the meantime, just wondering if it can be anything else?

[omega1oon]

mine did the same when both my wish bones had gone as thay wer floping all over the place but you need to sort them out fist to see if there is any other reason for it 

[symes]

Bottom arms flexing due to knackered bushes you answered your own question mate

[feeutfo]

Wobble is wishbone bushes as you say.

Rumble could be related, if the wishbone has slid down the bush and is resting on the subframe maybe.

Rumble....How old is the exhaust? You've had the dif serviced. Is the rumble front or rear?

[SMD]

It's not exhaust, that was changed August last year. Diff + oil was changed recently. Is the diff oil supposed to be sealed for life? Could it be low on oil?

It's not clear where the rumble is coming from. I would say central(ish). But I will pay more attention to it next time I'm out.

[omega1oon]

if it is central then it could be prop shaft out of balance as thats what happens with the trucks i work with just a thout but not thet likely

[SMD]

If it is the prop shaft, what/how to cure it? Sounds complicated and expensive

[omega1oon]

need to rool out the other possibilities first as it is highlt un likely but we send our shafts off to a place called HLSmiths for ballancing and center bearing replacement.
just replace the bushes first before you get to worried 

[SMD]

Ok - had new wishbones, rear donuts and tyres and problem is still there between 40-50mph. As already mentioned problem is there when coasting i.e. foot off gas pedal but goes away when cruise is engaged.

[feeutfo]

Hmmm, if it was dif or drive shaft related I would have expected poly rear donuts to make any vibration worse tbh.

Yet its better. Strange.

[SMD]

Hmmm, if it was dif or drive shaft related I would have expected poly rear donuts to make any vibration worse tbh.

Yet its better. Strange.

In the cabin, its queiter than its ever been. I don't think its the wheel bearings, I've had it on other cars and its not the same. 

[feeutfo]

Is the spare wheel secured tightly? Jack screwed in tight. That sort of stuff?

[SMD]

Is the spare wheel secured tightly? Jack screwed in tight. That sort of stuff?

Yes and yes. A while ago I had an annoying rattle and then squishy sound from the rear which was firstly the spare wheel not being secured properly (rattle) and then too tightly (squishy)    Everything at the back is now sound.

Could it possibly be onset of a gearbox related issue? Although currently no issues with gearbox other than a knocking sound when lifting of at 20mph which Kevin Wood says could be a side effect to the ECU update which he gets too.

[feeutfo]

I doubt it's an issue with the box. But on that subject it might be worth getting yours sevices btw.

But tbh, the only rumble like you describe that I've encountered was on Entwood the king pikeys car. Eventually cured when the dif was replaced. Iirc.

[Entwood]

I doubt it's an issue with the box. But on that subject it might be worth getting yours sevices btw.

But tbh, the only rumble like you describe that I've encountered was on Entwood the king pikeys car. Eventually cured when the dif was replaced. Iirc.

Mine was far more severe than described ... it didn't stop at 50 mph, it just got louder !!

It also got worse very quickly over a fairly short time/distance

There was never any vibration felt through the steering either.

It "might" be worth you trying what I did to eventually trace mine after a rear wheel bearing change made no difference....

Jack car up both sides as high as you can get it SAFELY on to good axle stands, then using bottle jacks or similar jack the wheels up (I used the bottom shock mount) until they are sitting in the "right" place relative to the wheel arches - you could always measure this before and after - I just guessed). This gets the drive shafts etc into their "natural" position

Now, hand brake off, run the car and drop it into gear .. on mine it very quickly settled down at just under 40mph without me touching the throttle !!

I could then crawl under the car and listen for the 'orrible noise ... quickly apparent it was the diff .. and pulling on the handbrake cable each side to stop each wheel in turn was pretty conclusive as well... 

Diff changed and all went quiet !!

Now, this might NOT solve your problem .. but it might eliminate the "back end" as the source and just leave the front as suspect