Damage to differential?

Damage to differential?

Author
Discussion

NDA

Original Poster:

22,326 posts

232 months

Saturday 28th December 2019
quotequote all
Just having two new rear tyres fitted on my Range Rover - the fronts are fine.

The guy fitting them said that I should change all 4 tyres as any difference in tread depth would damage the differential.... I’ve not heard this one before.

Test driver

348 posts

131 months

Saturday 28th December 2019
quotequote all
Technically he is right if you read the owners manual. Rotating the tyres helps but it’s scaremongering you sell more tyres really .

NDA

Original Poster:

22,326 posts

232 months

Saturday 28th December 2019
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The Range Rover is a tank - I can’t believe a few mil of tread depth would knacker the differential.

camel_landy

5,085 posts

190 months

Saturday 28th December 2019
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Bear in mind, depending on the age of your Range Rover you might have a vicious coupling instead of a diff-lock... This might get 'upset' if the rotational speeds, between axles, are too far out of sync.

M

bigblock

778 posts

205 months

Saturday 28th December 2019
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On a tyre size of 255/55/20 a 5mm reduction in tread depth equates to about 1.5% reduction of the circumference or 36mm. I think this would be well within the tolerances set by the manufacturer to allow both the differential and the traction control systems to operate correctly.

skyrover

12,686 posts

211 months

Wednesday 8th January 2020
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It will eventually destroy a viscous coupling 4x4 system.

It wont have much effect on standard open differentials.

NDA

Original Poster:

22,326 posts

232 months

Thursday 9th January 2020
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3mm of tread difference will 'destroy' a 4X4's coupling system?

Seems extreme.

skyrover

12,686 posts

211 months

Thursday 9th January 2020
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Plenty of examples out there. It can and will.

bigblock

778 posts

205 months

Thursday 9th January 2020
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skyrover said:
Plenty of examples out there. It can and will.
No it won't !

There is a degree of tolerance built into the coupling system of around 4% before lock up starts to occur which is more than enough to cover the difference between the rolling circumference of a new tyre and a worn tyre. If there wasn't then just fitting the new spare tyre after a puncture could cause the type of damage you are suggesting.

If you were to run excessively different tyre pressures or the incorrect tyre size then yes the coupling will sense the difference in road speed between the axles and try to lock up constantly, creating heat and wear which could eventually cause the type of damage you claim.

skyrover

12,686 posts

211 months

Friday 10th January 2020
quotequote all
I've known two ZJ jeeps and multiple Gen 1 freelanders with this issue.

One of the jeeps was mine.

The previous owner had run mismatched tyres for years... The transfer case was burnt out by 90,000 miles. No idea how many of those miles it took to ruin it.

There can be quite a difference between tyre's of different makes, especially in the off-road world.

Edited by skyrover on Friday 10th January 01:12

camel_landy

5,085 posts

190 months

Friday 10th January 2020
quotequote all
bigblock said:
There is a degree of tolerance built into the coupling system of around 4% before lock up starts to occur
The idea behind using a VC is to lock when there's a sudden change, e.g. a sudden loss of traction.

The tolerance is there to deal with situations such as driving around a corner. Whilst it's capable of dealing with occasional slippage, a constant slippage can damage them and/or other components in the driver train.

M

bigblock

778 posts

205 months

Friday 10th January 2020
quotequote all
skyrover said:
I've known two ZJ jeeps and multiple Gen 1 freelanders with this issue.

One of the jeeps was mine.

The previous owner had run mismatched tyres for years... The transfer case was burnt out by 90,000 miles. No idea how many of those miles it took to ruin it.

There can be quite a difference between tyre's of different makes, especially in the off-road world.

Edited by skyrover on Friday 10th January 01:12
I think that you are confusing a wet plate clutch system with a viscous coupling. The Gen 1 Freelanders used a Haldex centre diff with a wet plate clutch, this is not the same as a viscous coupling. After 1995 the ZJ Cherokees also used a wet plate clutch pack for the center diff. These can be much more sensitive than a viscous coupling and are prone to burning out the clutch plates with constant slippage. The OP's vehicle has a viscous coupling.


Edited by bigblock on Friday 10th January 14:56

bigblock

778 posts

205 months

Friday 10th January 2020
quotequote all
camel_landy said:
The idea behind using a VC is to lock when there's a sudden change, e.g. a sudden loss of traction.

The tolerance is there to deal with situations such as driving around a corner. Whilst it's capable of dealing with occasional slippage, a constant slippage can damage them and/or other components in the driver train.

M
The tolerance in the VC is there to deal with slight imbalances in the rotational speed of the front and rear axels caused by various factors including the difference between the circumference of a new and worn tyre within normal parameters. I don't think we need to scare people into thinking their drivetrains are going to fall apart because they have lost a few mm of tread !!

Edited by bigblock on Friday 10th January 14:56

camel_landy

5,085 posts

190 months

Friday 10th January 2020
quotequote all
bigblock said:
The OP's vehicle has a viscous coupling.
The OP hasn't actually stated...
...but if you look at the OP's garage, there is a RRS Supercharged in there.

So if that is indeed the subject matter for this 'splitting-of-hairs' commentary, the RRS actually has an eDiff, which uses a clutch system.

Either way, it is NOT an open diff, so therefore approach with caution. wink

M

NDA

Original Poster:

22,326 posts

232 months

Saturday 11th January 2020
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It is a Range Rover supercharged.

I fitted 2 new rear tyres and so far it hasn't blown up.

Nicks90

563 posts

61 months

Sunday 19th January 2020
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You'll see way more than 4% driving round a roundabout!
Does the owners manual tell you to only do tight manoeuvres 500 times before a major centre diff overhaul is required? Don't think so.

LandRoverManiac

402 posts

99 months

Tuesday 28th January 2020
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On LRs the Freelander 1 was the main one for ensuring all tyres were closely aligned - it could strain the driveline which wasn't all that robust to begin with...

Newer vehicles since have a certain amount of latitude in tyre difference front to back and and will be designed with a safety margin in mind. Older stuff cares even less so long as all four tyres are vaguely round!

Rotate the tyres every couple of thousand miles to wear them all equally and you won't have an issue.