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Well, I've been working on a brumby as of late and for the life of me can not work out the vibration issue.
Its fairly stock but has been converted to RWD.

Recently had all 4 shocks changed, all swaybar bushes, the pivot rear diff mount bush, both mustache bar diff bushes, tail shaft uni joints( both), gearbox mounts, ball joints and tie end rods.
It has a Y-pipe back straight through exhaust but the vibration was there before the exhaust was done.
The vibration is only there after 90kmhr or if you put it under serious load. Ie; 4th gear at 50kmhr.
4th gear at 70kmhr does not do it. If you put it in neutral at 100kmhr it is still there and does not change. Nor if you accelerate from 100kmhr onwards it does not change it.

The vibration is so bad you can barely hear the stereo, you can't even hear the road noise from everything ratting and you can physical ly not see out of any of the 3 mirrors.

Im thinking CV's, wheel bearings in the rear, engine mounts or tyres unbalanced.

Any ideas?

How old are the tyres?

To me it has to be tyre related - or wheel related anyway.

Are all of them round? Are the rims straight/true?

Are all hubs/axles straight? I found one of my hubs bent so bad it made a wheel wobble...

You've got some further investigation to follow.

Or worst case scenario there's something wrong with the rear diff or the gearbox...

Cheers

Bennie

Thanks ElFreddo

I've got some spare wheels and tyres I'll try out tomorrow.
Um unsure or how old the tyres are.

I know the front wheels are slightly unbalanced as there is some minor steering wheel vibration at some speeds.

The other thing I've thought about is the drive shafts - I had a set on my L that would oscillate at speed, the vibration wouldn't be there, then with a bend in the road the car was undriveable!

A new set of shafts did the trick. Might work for you too.

Why are you running rear wheel drive, apart from trying to be a P plater punk?

And was the vibration there before you made it rear wheel drive? Have a gearbox on hand for when the rear drive gears let go

Cheers

Bennie

+1 as they say- for tyres

RWD because FWD is utter crap. Hideous for carrying loads in the back ss the front wheels basicalky come off the ground.
In general just drives like a different car, much smoother and better round corners.

They'll only break if you abuse it.

I thought about the tyres but it also does it when you load it right up in 4th gear at low speeds, unless that is an entirely different problem all together.
No it didnt do it FWD, but it didnt do it RWD for quite a few months.

Would be looking at gearbox and diff mounts, as well as rear wheel bearings, if the spare tyres don't change the vibration issue.

TOONGA

Toonga,
All diff mounts and gearbox mounts are brand new.
Im thinking CV shafts or wheels. .. will have to check it out tomorrow. ..

Could be CV's/axles. I remember some unwanted vibrations disappearing from my ute when I put new shafts in, but they were front ones. So do you just run it in high range all the time? Thought you weren't supposed to exceed 60km/h in 4WD mode.

not exceed 60 kph ?? no one told me have a favourite stretch where the Brumby feels so well balanced at 110 in the dirt

Yeah High range all the time. Sometimes use low if im carrying 2-3 motors in the back.
Seems to run fine, flushed the gearbox and out some half decent (free :P) oil in thanks to City Toyota in Perth.
In the owners manual it doesnt state a max speed for 4wd high, just low range.
Runs good on the freeway and highway when in RWD, the steering is so much easier to drive with as you dont have any power at the front wheels now.

I have just finished changing the totally stuffed rear wheel bearings in the MY wagon and can say that while the bearings were not totally dry of grease they were water effected. There had been water ingress and grease leaking out onto the brake shoes from the seals.
I was experiencing a sort of whirring/grinding noise that could easily drown out the stereo at low to medium volume.
At no point was there any evidence of vibration. Just the horrid noise.

i had a severe wobble/shudder due to a bent front outer cv joint. although this was mainly only when under braking.

Had a shudder at 100ks+ on a car I owned turned out to be a tyre that had a high spot in the center of the tread on the rear

+1 for checking age of tyres ...

As the older they are the harder they get & more prone to damage ...
( Found that out the hard way, see my Brumby thread )

Cheers, Bantum ...

Found a set of stock 175/70R13's so I through them on all 4 corners.
Low and behold the vibration is still there.....

Put her back into FWD, without front shafts and ran her upto 110km/hr to see if any vibration occurred. This would help me investigate if it is any form of engine, gearbox or exhaust mounts.... anyway she was smooth as butter.

The wheel bearings seemed fine from my self diagnosis so I am leaning towards rear CV shafts or rear diff...
More investigation to be done in the meantime.

I've been thinking about this - my money is on rear drive shafts. They're probably the factory units, and since they're the ones doing all the work now I'd say they've worn out quickly yet quietly.

Replace them and you'll be sorted. Have fun getting them off if you've never had them off before! A slide hammer will come in handy

Cheers

Bennie

From the looks of the torsion bar they come out by dropping the rear diff out??

Remove/drop the diff to get them that last little bit off the output stub.

Cheers

Bennie

Too easy, thanks.
I'll attempt it at a later date...