[Jezzza]

Hi all,

I have a weird vibration in my 95 Vitara SWB
No lifted shocks or springs
New tyres to front, but had a full wheel alignment done (I think.. not actually sure if they did rear)
Tread looks even on both tyres
Feels and sounds like it is coming from the rear
Replaced whole exhaust recently, and still had same issue as with old exhaust

It only happens between 75-85km/h, once over the speed, its smooth and no vibration. No vibration under 75km/h either
I had the tailshaft uni joints done which fixed a really bad vibration in the rear. The only thing I question when the shop did my tailshaft, is that I handed my old one in to get unis done, but when I got the tailshaft back it looked like it wasnt actually my one but an already recon'ed unit

The vibration isnt that bad.. but can definitely feel it
Basically, if I put some coins on top of the dash in the "dipped" area, they will rattle

Any ideas what to look at?

[Grags]

If the tailshaft was out of balance or bent, then the vibration won't come and go, it'll just get worse
If it was the wheels out of round or out of balance they would just get worse as you went faster so we can also rule them out so..
Sounds like a 'harmonic' issue, without actually looking at the car I'd be looking at:
First is to determine if the vibration is related to engine speed or tailshaft speed (or road speed) eg is the vibration the same at a particular rev range( in 3 or 4th or 5th) or will it vary according to engine speed
If you spin up the motor while stationary, will you get a vibration?

If it's at tailshaft speed (or road speed), look at the parts that are related to the mainshaft of the g/box back to the diff
rear diff pinion angle, be sure it's as per factory specification (hopefully the a arm mount on top of the diff is on right way round)
check lower control arm bushings are OK and that the arms are not bent, all of which will mess with the pinion angle
Gearbox & engine mountings are nice and firm, not broken or sagged and the right ones for your car, crossmember not bent
The uncommon ones- going deeper, remove the tailshaft and check that the uni joints nice and free or are they binding, are they even on right? are the uni joints phased right (will be very uncommon that one look that up) is the g/box output shaft OK, not sure if anything in the transfer case can be a contributor, maybe some one else here has experience with that. is there any play in the diff pinion itself.
I should also mention, if the vibration was really bad with the old tailshaft and now it's slightly better, there's a chance that the gearbox output or diff pinion might have copped damage as a result of the bad tailshaft so pay special attention to those areas

if the vibration is engine speed related then check if:
Exhaust is mounted correctly, yes you have had it replaced but doesn't mean that it's mounted right
brackets, other mounts etc attached to the engine, all of which can rattle/vibrate at certain revs if not mounted correctly or cracked/broken etc

One thing I came across on another brand of 4wd, of the freewheel hubs are dry of grease, then the shims etc in there might do a bit of harmonic style chatter but you'd know it was in the front

Hope that helps you narrow things down, good luck
cheers

[30ONA]

Check the easy things first. Like above try to eliminate components. Unlike above I disagree on the tyre/wheel roundness. Because you have dampers and springs they will try to counter an out of round wheel or tyre. You can balance an out of round object. Ever watched myth busters driving with square wheels? At the right speeds you won't feel out of round. Also check wheel bearings.

[alien]

Check the wheel studs are all done up =)

[Gwagensteve]

All/any vibration can be speed dependent.

Check balance/roundness of rear tyres firstly.

Tailshaft can't be out of phase- there's no slip yoke in the rear tail shaft of a vitara.

Excessive suspension lift can cause vibration, so could a bent gearbox crossmember - as has been pointed out, due to pinion angle. SWB Vitaras are quite sensitive to changes in pinion angle.

Steve.

[Grags]

Just saying I've seen repaired tailshafts out of phase so check it none the less and tick it off the list if it's OK

[Gwagensteve]

Ah yes - now I see what you're getting at - welded up out of phase. Yes, well, I guess that's possible, eek!

[30ONA]

I've had this too on a300zx. Brand new shaft made for the car but the tube was bent. Balanced but that's at a fixed speed. Then wack it on a car at various speeds. It is usually pretty obvious though and the whole car shakes, you feel it through the seat.

[Jezzza]

Grags wrote:

Just saying I've seen repaired tailshafts out of phase so check it none the less and tick it off the list if it's OK

What do you mean out of phase?

Thanks all.
Will rotate rear wheels on the weekend
It feels like it comes from the rear, only at 75-85km/h

Even in 4th gear it does it. So leaning towards something suspension related

I was speaking to a mechanic mate, and he said could be the tailshaft not being balanced properly?
I gave my old tailshaft to a reputable shop in WA.. I marked the tailshaft and diff joint.
When I got it back, it was clean as a whistle, and no marks on the diff end
Also, the tailshaft didnt actually appear to be mine, as it had a small plate welded to the side of it (for balancing?)
I havent had experience with getting unijoints done before.. only ever took out my old one and put it back in to do gearboxes
I assumed that if the tailshaft is balanced, then doesnt really matter how it connects? Sort of like tyres, if they are balanced, they can go front or rear, left or right
Would this be an issue? I got it done a few months back.. not sure if the shop would remember me now
Im going to try and rotate the tailshaft on my diff

[alien]

If it's the tailshaft and you have some stands - jack up the rear end, chock the front and spin dem wheels up! Bonus points if you have someone else to that part while you look around at what's wobbling.

[Grags]

Phasing is the alignment of the yokes at either end of the tailshaft
Typically the yokes on a one piece shaft are aligned exactly like for like so if you drew a straight line from the centre of the uni-joint cap of the front yoke (that is welded to the tailshaft), then it should be precisely aligned with the corresponding rear yoke (that is also welded to the tailshaft)
I might add I've see an occaisional tailshaft twisted but that's after a big horsepower event involving slicks and a sticky drag strip.......probably not the case here hahar

[BlueSuzy]

Does it have weights on it?

Tailshaft repairs and the way they are made NEW can be pretty agricultural. I've had a standard jimny jackshaft on a lathe to shorten it for my sierra. The tube was at least 1mm off centre where it was welded to the uni section...


Phasing:




Check your pinion angles. On standard uni's. They must be equal degrees. Bent crossmember can make it go out. Worn diff bushes and top ball joint can make the angle go out also.

[vet 180]

My bet is tyres/wheels out of balance.

[alien]

can't be bothered reading above again - but if you've driven any mud recently - is there mud in the rims? Cos that'll give a good wobble!