Help needed on identifying mystery noise

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baldrick56

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OK confession time - its not French - but it could be (at least for RWD French). I'm getting a noise I think from the driveline of my (new to me) Ute, up to about 70 kM/h its not there (or at least too quiet for my ancient ears to detect), but over that speed there's a 'booming' (or like incredibly rapid drum-roll) getting progressively worse until about 95 kM/h after which it appears to recede a bit. The other major factor is it disappears instantly on the overun. So if you're on cruise control it comes in and goes out dependent on slope / headwind etc.

Vehicle is RWD with non full-time 4WD, selected by rotary switch on console (must be electric servo to actually move the gears) - I haven't used 4WD at the sort of speeds listed above to see if its any different. The front hubs are 'freewheeling' so I guess the front propshaft shouldn't be rotating at all when in 2WD? Only had the veh a few months (& irritatingly test drove it only in urban surroundings no never got more than about 60kM/h :(). Recently needed to go to Melbourne (ca. 900kM) in it and prior to that journey I jacked it up, checked levels on Rear axle, Front axle, gearbox, transfer case. Also hit all the greasepoints on the UJ's with generous squirt of grease (they'd probably never been done). Overall its nine years young & done under 100,000 kM, can't say the Melbourne round trip has made things noticeably worse (or better) - that might've been 'cos I had the musak turned up high enough to make my ears bleed for most of the trip :rolleyes:

Any ideas where to look next?
Thanks,
Rob
 
Is there a brand-specific forum out there? They can be very good. For example, the Renault UK forum is excellent for Scenics, since they sold so many there, relative to here.

It might be a single minor thing that is model specific. I had what we thought was an exhaust noise, most irritating and eventually it was a damaged bearing retainer bracket on the intermediate bearing on a front drive shaft. It was found by accident - I'd not have found it in a lifetime.
 
It hasn't been played with height wise? Fitting a lift kit can upset the driveshaft angles enough to cause symptoms similar to what you describe.🤷‍♂️
 
Having re-read the first paragraph in post #1 I'd like to revise what I think it might be, because you say it disappears on overrun I would say that the noise is coming from the crown wheel and pinion.

Wheel bearing noises come and go with speed and load variations but do not go away on overrun.
 
My experience is with old LandRover, but free wheeling hubs only disconnect the drive power at the hub using a one way clutch.

Noise disappearing in over-run could be a gear in some part of the transmission, not only the diff set up. but also a transfer gear. Most 4WDs and commercials don't use hypoid diffs, but setting the crown wheel and pinion correctly for them is a fiddle not thought of by many home mechanics. With simpler Landie and truck diff geometry with the pinion centred on the wheel there is still a lash and float procedure. You can find videos.

Is there a possibility of a repair before you got it?
 
You might have the front wheels free, but I bet the transfer case is still turning the front prop shaft and diff. Try lifting the rear wheels and look under the car to see if the front driveline is spinning.
 
That depends on transfer locking. Not everyone has full time 4WD. The red knob in a series LandRover engages/disengages front drive in the transfer case by direct mechanical connection. There was no centre diff.

This vehicle discussed has an electric engagement. The hub clutches can still want to turn the prop shafts, but with no power.
 
Being a lateish model 4x4 ute I'd be checking whether it has had a suspension lift as first point of call. Even a 2" lift on many of these later vehicles can cause issues. Often a spacer is required to lower the center bearing to prevent harmonics that present themselves as described in the OP symptoms.

Same but different. A guy I know had a 2" suspension lift, and slightly wider wheels and tyres fitted to his 300 Series Landcruiser. It wasn't a Toyota authorised company that did the suspension work, but it was a very reputable, well known, nationwide supplier.
It randomly would start to shake the steering wheel driving down the highway and this would escalate to the point where the entire vehicle would start shuddering and veer off the road.
He had it checked by 2 different Toyota dealers (it only has 20K kms on it) and a couple of independent mechanics and they all said "there is nothing obviously wrong".
The fix? He put it back to standard.
Best part is, his brother has the same model vehicle with similar kms and very similar mods and has not had the same problem.🤷‍♂️
 
Greenpeace said:
Being a lateish model 4x4 ute I'd be checking whether it has had a suspension lift as first point of call. Even a 2" lift on many of these later vehicles can cause issues. Often a spacer is required to lower the center bearing to prevent harmonics that present themselves as described in the OP symptoms.

Same but different. A guy I know had a 2" suspension lift, and slightly wider wheels and tyres fitted to his 300 Series Landcruiser. It wasn't a Toyota authorised company that did the suspension work, but it was a very reputable, well known, nationwide supplier.
It randomly would start to shake the steering wheel driving down the highway and this would escalate to the point where the entire vehicle would start shuddering and veer off the road.
He had it checked by 2 different Toyota dealers (it only has 20K kms on it) and a couple of independent mechanics and they all said "there is nothing obviously wrong".
The fix? He put it back to standard.
Best part is, his brother has the same model vehicle with similar kms and very similar mods and has not had the same problem.🤷‍♂️
Click to expand...
Funnily enough the design engineers set the 4X4s up correctly for angles fo driveshaft joints, high speeds on the road and all that. They know what they are doing, like wheel and tyre sizes. Then owners go and mess up just one aspect, like ride height in isolation from quite a few other things that WERE part of an intergrated design. Other factors then come into play. Who'd be surprised?
 
Thanks Guys,
some food for thought there - it's not been 'lifted' height wise - springs / shockers are stock (leaf at rear, torsion bars front). It could've had some repair done on rear axle - its definitely been 'used' for 4WDriving - there's impact damage on the lowest bolt-on crossmember (this doesn't seem to support anything transmission-wise).
Regards,
Rob
 
Turned out to be a combination of Tailshaft centre-bearing & worn universal joints. Garagiste managed to find a good secondhand tailshaft that lessened the financial blow somewhat. Seems like driving a Rolls Royce now - comparatively :rolleyes:
 
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