Diff lock vs viscous diff?

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MikeV8SE

MikeV8SE

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OK, quick question - and yes I have searched and no, I can't find the answer I'm looking for!

We went to our first Pay & Play day today (4x4withoutaclub, Aldermaston - nice bunch and great venue!) in my mates Disco - a 1994 3.9 V8 auto with manual diff locks.

The car was great, brilliant in fact (given it was standard, bar some underbody protection!) and one thing that was really useful was if we did get a bit stuck, particularly in deep mud or cresting hills where the sills made contact, we could roll back, engage the diff lock, and it would pull us out/up/over as required! Kind of a safety net I guess, and very useful.

Now, my 1991 RRC (also a 3.9 V8 auto) has a viscous coupling rather than a manual diff lock, which means I can't choose to lock it when I want. Is this a disadvantage?

So, my question is this - which of these is the better solution in an offroad environment, and are there different techniques to using a VC rather than a manual diff lock?

Cheers! :)
 
vc is better it gives you diff lock without having to engage it.the effect is the same in that your both have locked center diffs but yours will give a bit to go round corners,the bit about v8 and auto are more preferable,as auto boxes allow you to deliver very little torque to wheels in slippy conditions or alot when required hence name torque convertor,for difflock to be really effective it needs to be applied before you get stuck but limits your steering ,vc is in all the time ,thats why i fitted mine to v8 auto disco
 
I'm currently on my 2nd range rover, my 3.9 had a viscous coupling, and my current 3.5 has the manual. I'm told by many others that the "viscous coupling will do the job for me anyway"
Problem with the viscous coupling that even though it worked fine, I do prefer my manual one because I know my front & rear proper are perminantly clocked when im on a "play and pay" site for example.
I'm im wanting 100% traction getting up a steep incline and with the viscous coupling, i'll loose traction momentarily before it engages diff lock automatically and I did find only sometimes loosing that traction momentarily was the difference between me me either climbing the incline or not :s.

Thats why I brought the 3.5 actually, as I knew I could then just leave it in diff lock, and take it out when I wanted to (providing I didnt wind the tranny up slightly)

The front & rear prop being locked up (as thats all it does on these range rovers as standard, hence both the diffs spinning at the same time) what i'd love is air locking diffs.
I would then have the standard diff lock engaged to lock up the props, then locking up whichever axel or individual wheel I choose via the air :)

Expensive :s
 
Thanks for the repsonses guys. I've been green laning in mine and had no problems, but at the pay & play day yesterday it was definitely useful to be able to lock the diffs when required! Can use it as a safety net for a start - so go everywhere without them locked but, if you do get stuck, at least you have that to fall back on!

I might add here, I'm not on about really serious offroading, just green laning and the odd pay & play day! So I am sure both options will be fine, but I think ideally I would like the control of manually locking diffs. Oh well!
 
MikeV8SE said:
Can use it as a safety net for a start - so go everywhere without them locked but, if you do get stuck, at least you have that to fall back on!

I might add here, I'm not on about really serious offroading, just green laning and the odd pay & play day! So I am sure both options will be fine, but I think ideally I would like the control of manually locking diffs. Oh well!
Click to expand...

T'is best to read the terrain and engage diff lock before you get stuck ;) :D
 
Bromsgrove Defender said:
T'is best to read the terrain and engage diff lock before you get stuck ;) :D
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Yes and no! I do agree to an extent, BUT if you get stuck with diff locks engaged then that's it, you're stuck! So until you can get a tow/winch out, you're staying put!

However, if you leave them open until such time you get stuck then you've got the diff lock as a last resort to get out of trouble, which can be very useful!
 
MikeV8SE said:
Yes and no! I do agree to an extent, BUT if you get stuck with diff locks engaged then that's it, you're stuck! So until you can get a tow/winch out, you're staying put!

However, if you leave them open until such time you get stuck then you've got the diff lock as a last resort to get out of trouble, which can be very useful!
Click to expand...


:doh:

You will damage your centre diff is your not careful its far worse to the transferbox unlocked ANYWHERE where grip may be reduced i.e (Non Tarmac) especially if you get stuck and spin up ONE wheel or one axle than to run it locked on Tarmac. I for see many a worn centre diff coming your way if you Honestly do not lock your diff when off any surface that has high grip.
 
MikeV8SE said:
Yes and no! I do agree to an extent, BUT if you get stuck with diff locks engaged then that's it, you're stuck! So until you can get a tow/winch out, you're staying put!

However, if you leave them open until such time you get stuck then you've got the diff lock as a last resort to get out of trouble, which can be very useful!
Click to expand...

No sorry your wrong. :D

If you've got your Diff Locked you're less likely to get stuck in the first place ;)

Which is why if you look at any Off Road driving technique manual, or ask anyone who regularly drives off road it/they will tell you always engage Diff Lock in any situation where traction may be lost, before traction is lost.
 
jai_landrover said:
:doh:

You will damage your centre diff is your not careful its far worse to the transferbox unlocked ANYWHERE where grip may be reduced i.e (Non Tarmac) especially if you get stuck and spin up ONE wheel or one axle than to run it locked on Tarmac. I for see many a worn centre diff coming your way if you Honestly do not lock your diff when off any surface that has high grip.
Click to expand...

Errr I've not got a clue what your on about :confused:

You seem to be saying that you should have your diff Locked at all times when off road :(

If your saying it's not good to high rev and spin out a wheel in Low range I agree I think..... :D
 
Last edited:
Honestly. Lock that diff! On grass, on gravel on anything thats not a high grip surface. Don't be scared of Trans wind up and failure will only occour if you drive for hundreds if not thousands of miles on a high grip surface with decent tyres. It Will increase drivetrain wear but not blow up or destroy itself unleass already knackared. The tyres chirping, drivetrain tighness and heavy steering will notify you that difflock is engaged unless you have absolte no feel for the vehicle. Not engaging the centre diff and spinning up ONE axle Will damage it the centre diff is not made to take much differential for any period. The differential between front and back speeds are not huge when on road with grip.
 
We do sometime unlock the centre diff and hold the handbrake on around tight corners while accelerating but this is for competition and if you've cocked up a turn trialling but this puts serious stress on the diff.

Bottom line:

If traction is likley to be broken engage difflock.

VC are good and very smooth if you see how much differential it takes to "lock" the VC then you will understand how little differential there is between axles when driving on road with grip.

Down side to VC is the ratio they are all 1: 1.208 or somthing similar whereas you can get an LT230 from 1:1.003 1:1.22 1:1.4 & 1:1.6 ratios so its swings and roundabouts. both will do fine borg warner is considered better but when it goes wrong is expensive to repair Lt230 is fine after all your main concern is that the centre diff is locked and doing this manually is just fine.
 
Honestly. Lock that diff! On grass, on gravel on anything thats not a high grip surface. Don't be scared of Trans wind up and failure will only occour if you drive for hundreds if not thousands of miles on a high grip surface with decent tyres. It Will increase drivetrain wear but not blow up or destroy itself unleass already knackared. The tyres chirping, drivetrain tighness and heavy steering will notify you that difflock is engaged unless you have absolte no feel for the vehicle.[/quote]


This is so wrong and why viscous diff's were invented :(


jai_landrover said:
Not engaging the centre diff and spinning up ONE axle Will damage it the centre diff is not made to take much differential for any period..
Click to expand...

Nearly right it's not designed to take excessive differential for any period.

jai_landrover said:
The differential between front and back speeds are not huge when on road with grip..
Click to expand...

Untill you want to go round corners ;)


jai_landrover said:
If y ou are likley to spin a wheel or likley to break traction lock that diff
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Absolutely spot on :D :D
 
when you go around corners the differential between front and rear propshaft speed is surprisingly small.

VC were only fitted to the RRC the hi end of the then luxury SUV market considered more expensive and a better but stretched chains and seized coupling puts me off.

Be honest How many transfer boxes have blown up because they have been driven in Difflock on the road? I bet there are a few but they never went bang straight away it was only if driven for many many many miles. Most causes were Farmers wives that knew no better and drove for hundreds or thousands of miles before failure occoured. how many trans boxes broken by leaving them in th eopen positionand spinning up wheels I've seen soo many I can't couont them by numpties at P&P just blatting about in fact its paid for many of my own LR parts selling them good used parts
 
With so many seized VC's on Borg warner boxes and Freelanders how many of those have broken any other part of the drive train on the road? Excessive wear Yes and agreed its not good for anything but this Wind up scares people into not putting difflock in.

How many seized VC's RR and Freelander have made somthing fail on the vehicle? Tyres might scream, drive train under more stress but the tyres will usually slip especially if they are offroad biased way way before breaking anything and any half decent driver will know there is somthing wrong way before damage or excessive wear likley to cause issues occour.

People just seem scared to put difflock in these days
 
jai_landrover said:
VC were only fitted to the RRC the hi end of the then luxury SUV market considered more expensive and a better but stretched chains and seized coupling puts me off.
Click to expand...

Nuthin worse than stretched chains and siezed coupling :eek: :eek: :eek: :D

I'm slowly coming to the conclusion that in the most part I agree wiv ya, but I never engage Diff Lock unless I suspect that traction will be lost and then disengage it at the earliest opportunity.
But then again thats because I think I read the terrain well enough to do that..............
I've never spun a wheel when out of Diff Lock .......................YET :eek: :D
 
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