"Clang" on hard throttle

domino · Jan 19, 2015

I've had this problem since I got the car however I always put it down to the tyres. After having a friend who's a mechanic drive it, he reckons it's something to do with a driveshaft or similar.

Basically, from a stand still (or driving slow) if you plant your foot on the loud pedal there are loud clangs to be heard and felt. The only way I can describe it is as though the wheels are skipping, losing traction, and the resulting noise/feeling is the wheels regaining traction. The noise is akin to a clang/pong type thing - like tension is being applied and then lost. I don't know if that makes much sense?

It has mud/snow tyres on it at the moment (on 3 corners) but as I say, he thinks it's something else and not tyre related.

I also get a noticeable vibration above 70mph on the motorways.. similar to what you'd experience with unbalanced wheels but more noticeable. The wheels have all been balanced and are spot on so I know it's not that but again, he thinks it could be related?

fanatic · Jan 19, 2015

Transfer box chain

Saint.V8 · Jan 19, 2015

Have you checked the VCU?

wammers · Jan 19, 2015

You should not be feeling this on the motorway. The speed limit is 70 MPH.

domino · Jan 19, 2015

fanatic said:
Transfer box chain

Wouldn't this affect the transmission in general, too? It's very smooth otherwise and changes up and down without issue.

Saint.V8 said:
Have you checked the VCU?

Forgive my ignorance.. but what's the VCU?

wammers said:
You should not be feeling this on the motorway. The speed limit is 70 MPH.

I was, uh, in Germany at the time?

Saint.V8 · Jan 19, 2015

domino said:
Wouldn't this affect the transmission in general, too? It's very smooth otherwise and changes up and down without issue.

Forgive my ignorance.. but what's the VCU?

I was, uh, in Germany at the time?

The Viscous Coupling Unit....

As the Range Rover is a permenant 4WD vehicle, when going round corners on hard surfaces, the front and rear axles will turn at different speeds, to combat this, there is a centre differential. This allows the two axles to rotate a different speeds but maintain drive.

Now, when you head to the slippier stuff (mud, etc) if one axle gets bogged down, or if finds low friction...and is slipping, a normal differential will send power to the axle with least traction (not what you want off road and you're stuck!) so to lock the centre diff, they used a Viscous Coupling that works very similarly to a gearbox torque converter...

Inside the VCU attached to each propshaft is a rotor..in the middle (I think) there is a stator (a fixed rotor)...

When one axle starts turning faster than the other, the rotors start spinning the fluid on oneside faster than the other...this swirling of the fluid across the stator to the other rotor warms the fluid inside the VCU and it starts to thickens up and starts to drag the other rotor attached to the other propshaft around with it....essential locking the two propshafts together to give maximum power to both axles simultaneously.

In some cases when they get old or over used they can lock up permenantly causinf knocking and scrubbing of tyres etc...this can lead to diff failure or gearbox issues!

To test....

Jack ONE wheel up, gearbox in Neutral, handbrake off (I think - others to confirm) and turn the raised wheel...it should be very stiff, use a wheel nut spanner as a lever...if it is locked solid....likelihood is the VCU is duff and locked up....

Datatek · Jan 19, 2015

Saint.V8 said:
The Viscous Coupling Unit....

As the Range Rover is a permenant 4WD vehicle, when going round corners on hard surfaces, the front and rear axles will turn at different speeds, to combat this, there is a centre differential. This allows the two axles to rotate a different speeds but maintain drive.

Now, when you head to the slippier stuff (mud, etc) if one axle gets bogged down, or if finds low friction...and is slipping, a normal differential will send power to the axle with least traction (not what you want off road and you're stuck!) so to lock the centre diff, they used a Viscous Coupling that works very similarly to a gearbox torque converter...

Inside the VCU attached to each propshaft is a rotor..in the middle (I think) there is a stator (a fixed rotor)...

When one axle starts turning faster than the other, the rotors start spinning the fluid on oneside faster than the other...this swirling of the fluid across the stator to the other rotor warms the fluid inside the VCU and it starts to thickens up and starts to drag the other rotor attached to the other propshaft around with it....essential locking the two propshafts together to give maximum power to both axles simultaneously.

In some cases when they get old or over used they can lock up permenantly causinf knocking and scrubbing of tyres etc...this can lead to diff failure or gearbox issues!

To test....

Jack ONE wheel up, gearbox in Neutral, handbrake off (I think - others to confirm) and turn the raised wheel...it should be very stiff, use a wheel nut spanner as a lever...if it is locked solid....likelihood is the VCU is duff and locked up....

Handbrake on.
Three tyres of one type and an odd one will not help.

domino · Jan 19, 2015

Datatek said:
Handbrake on.
Three tyres of one type and an odd one will not help.

Hey Keith. Yep, the tyres issue is in my mind though ultimately I don't think this is the cause of either the clunking or the wobble at speed however they will all be getting replaced in the next few months.

Datatek · Jan 19, 2015

domino said:
Hey Keith. Yep, the tyres issue is in my mind though ultimately I don't think this is the cause of either the clunking or the wobble at speed however they will all be getting replaced in the next few months.

Different rolling radius's can stress the VCU and knacker it.

wammers · Jan 19, 2015

Datatek said:
Different rolling radius's can stress the VCU and knacker it.

Won't do the diff on that axle a lot of good either.

holidaychicken · Jan 19, 2015

fanatic said:
Transfer box chain

+1

Thats where my money is..

How To: Replace transfer case drive chain

ovalandrover · Jan 20, 2015

Check bolts holding the handbrake drum

domino · Jan 20, 2015

holidaychicken said:
+1

Thats where my money is..

How To: Replace transfer case drive chain

And looking at that post I either need to get very friendly with the local indie or cancel the wedding! :O ££££

Grrrrrr · Jan 20, 2015

fanatic said:
Transfer box chain

Is there a way to test this? Maybe rock forwards and backwards or something?

holidaychicken · Jan 20, 2015

I know its been diagnosed and misdiagnosed using a 6 way diagnostic electronic stethoscope, well I partially misdiagnosed mine as I still have further issues to solve.
Have a look at my clunk thread although it's much more common on the P38.

The electronic stethoscope has 6 separate microphones which you clip to various parts of the vehicle and then switch between the mics to see which is loudest and gradually narrow it down

domino · Jan 20, 2015

I've got an LR specialist coming to see the car tomorrow evening. Will have him out in it so he can have a listen and take it from there

Thanks all!

tomcat59alan · Jan 20, 2015

While you are under, check the torque converter is bolted tight to the flexi plate.

"Clang" on hard throttle

domino

Well-Known Member

fanatic

RESPECT IS EARNED, BEATINGS ARE FREE ;-)

Saint.V8

Dyed-in-the-wool 100% RR Junkie

wammers

No longer with us, RIP

domino

Well-Known Member

Saint.V8

Dyed-in-the-wool 100% RR Junkie

Datatek

Well-Known Member

domino

Well-Known Member

Datatek

Well-Known Member

wammers

No longer with us, RIP

holidaychicken

Well-Known Member

ovalandrover

Well-Known Member

domino

Well-Known Member

Grrrrrr

Technician, Bodgit & Scarper Ltd

holidaychicken

Well-Known Member

domino

Well-Known Member

tomcat59alan

Well-Known Member

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