do locking diffs save halfshafts?

[02GF74]

been thinking about a locking diff and reckon they are kinder to half shafts so wondering if my reasoning is correct. Apologies if this has come up before!

case 1.

Consider a 2 wd truck with an open rear diff with engine running at constant speed so both rear wheels turn as speed S. If one of the rear tyres loses grip, it will now spin at 2 S, other wheel will have stopped resulting in the truck not moving.

Once it regains grip, it will be stopped before the truck starts to move eventually to turn at S. I say stop since the truck itself has stopped so the wheel must too? (it will happen momentarily)

So one wheel gets stopped from a speed of 2S to 0, then both wheels move off to eventually reach speed S.

case 2

Consider an identical 2 wd truck but this time with a locked rear diff. If one of the rear tyres loses grip, both wheels continue to turn at S and truck keeps moving. If the other wheels loses grip, then both wheels spin at S with the truck not moving.

Once one wheel regains grip, it will be stopped before the truck starts to move eventually both wheels to run at S.

This time both wheels get stopped from a speed of S to 0, before both wheels move off to reach speed S.

summary

If the above reasoning is correct, you are less likely to break a half shaft wtih locked diff since the wheels will be stopped from S as opposed to 2 S for open diff. Is that right or not?

[white90]

No they are not kinder

they transmit all the power to one wheel if the other is in the air or slipping

so x2 the amount of torque it was design for is being applied.

if they were kinder why would anyone fit uprated shafts? kind of answers your question really

[02GF74]

No they are not kinder

that transmit all the power to one wheel if the other is in the air or slipping

so x2 the amount of torque it was design for is being applied.

if they were kinder why would anyone fit uprated shafts? kind of answers your question really

right; I've thought about it some more.

in my first post I did not consider the effect of torque - but was only consdering what happens when trying to stop a rotating wheel. (flywheel effect?).

I also thought about the above ^^^^^ and it is not the whole story and will attempt to illustrate.

** Torque only exits when something tries to stop something else from turning. **

Consider the case with locked diff, when one wheel is in the air.

- if the other wheel has grip, then the torque supplied by the engine and going through the drive train will be that what is required to keep the truck moving at the given speed. sine it is not being shared by both wheels, all the torque will go trhough 1 halft shaft.

- if other wheels spins, this maens there is insufficient grip to hold that tyre so there may be more or less torque than when moving, I reckon less for example consider the wheel on ice.

Now torque comes into play when the spinning wheel suddenly get gripped by the ground - the engine will try to turn the wheel increasing torque through the half shaft until either

a) the wheel start to move along the ground so nothing is stopping the wheel from turning

B) the wheel spins again

c) the engine is unable to supply more torque and stalls

d) the drive train pops due to more torque being put through it that it can take.

In the last case, because the other wheel is up in the air and nothing is stopping it from moving, torque from the engine is not shared thus will go though the one halfshaft and engine is supplying close to its maximum torque.

[John_T]

Tony is of course quite right in his reply. However, we are talking thoery as opposed to actual use.

My understanding is (and I am happy to be corrected) that the majority of halfshaft breakages are caused by the shock loading resulting from a spinning wheel suddenly regaining some grip. As opposed to the scenario Tony is citing of loadsa power being transmitted to one wheel. As the chance of a single wheel spinning is reduced by a locker it follows that breakages should be less and hence lockers are kinder to halfshafts.

Of course, all of this depends on how the truck is driven but I am assuming average driving technique and some sympathy for the transmission!

[will_warne]

02, with my front diff open I never break front axle components, with it locked I break quite a lot

If 3 wheels have lost grip you're putting a lot of load on the only corner that has drive.

[john cranfield]

Tony is of course quite right in his reply. However, we are talking thoery as opposed to actual use.

My understanding is (and I am happy to be corrected) that the majority of halfshaft breakages are caused by the shock loading resulting from a spinning wheel suddenly regaining some grip. As opposed to the scenario Tony is citing of loadsa power being transmitted to one wheel. As the chance of a single wheel spinning is reduced by a locker it follows that breakages should be less and hence lockers are kinder to halfshafts.

Of course, all of this depends on how the truck is driven but I am assuming average driving technique and some sympathy for the transmission!

From personal experience both of the above scenarios are correct so a judgement has to be made. In the conditions you are likely to be driving will a lack of a spinning wheel cause a torque over load on the wheel with grip or will a spinning wheel suddenly grab and expose the 1/2 shaft to a high shock load?. I have noticed that the torque over load is more likely to happen but hard to detect by the driver. If the open diff allows a wheel to spin the driver can back off to reduce the shock.

In sumary a locker is likely to be harder on 1/2 shafts and weak diffs.

John

[reads90]

No they are not kinder

they transmit all the power to one wheel if the other is in the air or slipping

so x2 the amount of torque it was design for is being applied.

if they were kinder why would anyone fit uprated shafts? kind of answers your question really

i disagree with you tony

I have found and thought in the past that on the rear axel (and can be said fir the front). Having the locker in stops spin on one trye when going up hills or over difficult terran. And we all know that you break a half shaft when the tyre is spinning and then comes down on the ground, or grips and suddenly stops. this then buggers the shalft as the trye stops it one end and the dif wants it to turn the other end. With a locker in the trye will only spin at the speed that the other wheel is moving so hence no fast spinning tyre.

I used to over use the locker just for this case, and it worked well. After all the same does go for the front,and that was the design and idea of the gkn overload protecters, to take out the force of a spinning tyre coming to a stop suddenley

Why we are running uprated shafts tony is because the 90 came out of the factoury with 205 R16 Mich M&S

and not simex 35" tyres

[white90]

i disagree with you tony

I have found and thought in the past that on the rear axel (and can be said fir the front). Having the locker in stops spin on one trye when going up hills or over difficult terran. And we all know that you break a half shaft when the tyre is spinning and then comes down on the ground, or grips and suddenly stops. this then buggers the shalft as the trye stops it one end and the dif wants it to turn the other end. With a locker in the trye will only spin at the speed that the other wheel is moving so hence no fast spinning tyre.

I used to over use the locker just for this case, and it worked well. After all the same does go for the front,and that was the design and idea of the gkn overload protecters, to take out the force of a spinning tyre coming to a stop suddenley

Why we are running uprated shafts tony is because the 90 came out of the factoury with 205 R16 Mich M&S

and not simex 35" tyres

We'll I'm running uprated shafts as I have fitted ARB's

breakages so far have been caused only when the ARB has been engaged

always o/s CV no wheels in the air just loading the Cv with too much torque

once on M/T one on Simex so far

standard shafts may have gone first I'll never know as I replaced them with M/D.

I see the original question as "are they kinder" I can't see how they can be kinder forcing a wheel to try and move the vehicle when the other is turning in mud or the air.

[reads90]

We'll I'm running uprated shafts as I have fitted ARB's

breakages so far have been caused only when the ARB has been engaged

always o/s CV no wheels in the air just loading the Cv with too much torque

once on M/T one on Simex so far

standard shafts may have gone first I'll never know as I replaced them with M/D.

I see the original question as "are they kinder" I can't see how they can be kinder forcing a wheel to try and move the vehicle when the other is turning in mud or the air.

mmm it bit of 6 of one and half a dozen of another

The goldern rule is to engage lockers before you go in (as such) the big no no is engaging them when stuck as this does lead to what you are saying . One in the air and one stuck and the diff trying to turn a stuck wheel. But on hill climbs they are definatley kinder to the shafts.

I ran stanard shafts with locker and only had one problem and this was my own stupid fault for doing what i said was a big no no .

If you have a locker in and a wheel is stuck and another is in the air then this is the time the driver takes a bit of sense and works out he is stuck and gets the winch out before the red mist comes out

But you can still break a shaft with this if the locker is out, you have spining and the other stuck if the one that is spining gets grip it will too break a half shaft.

Most about off road driving is to look after the truck and to admit when you are stuck and not to cause damage or more damage

I pride myself that on my 90, i did only one half shaft on the rear (stanard was with a simex the one mentioned above) and no cv's on my truck at all in all the time i owned it (even before i had the GKN overload protectors fitted to it), but was never seen to be holding back

as for your breakages have you thought that it might be your driving style after all from what i have seen of your truck it does like to eat parts at events

I watched you at the last slindon event take a hill at speed and reving the nuts of your truck trying to get to a punch. You had the wheels in the air and coming back down with a thump. It took you ages to get to the punch and alot of stress on your truck Me and tonk were watching you waitng for the noise which you were lucky did not come. We did it quicker and did not even drove it just winched up to the pucnh and winched back down

[Tonk]

so wot u're sayin ali is summat that we already know, tony cant drive

personally i think lockers r better engaged cos its stops one wheel spinning up, a spinning wheel which is suddenly stopped when it comes back to earth normally breaks summat imo

[white90]

O my word a comedy double act!

Eat parts at events?

1 CV and 1 shock can hardly be described as eating parts can it?

the CV was my fault trying to reverse out with the front locker in

The shock who knows the welded eye just snapped off.

Last Slindon and since I've bust nothing, probably because it is well put together with decent parts who knows?

As for driving style thats purley personal horses for courses I guess I'm always happy to watch and learn

not being an expert an all.

Mark

ooo how I laughed!

[RPR]

If you don't have lockers, you're more likely to break halfshafts when the shock of a spining wheel returning to the ground breaks it. If you have lockers, your going to be able to drive bits that apply higher than acceptable torque to one or more half/shaft, but you might break CV's too. If you use a Land Rover as God intended, you're going to break bits, the only questions are which ones and how.

[02GF74]

If you don't have lockers, you're more likely to break halfshafts when the shock of a spining wheel returning to the ground breaks it. If you have lockers, your going to be able to drive bits that apply higher than acceptable torque to one or more half/shaft, but you might break CV's too. If you use a Land Rover as God intended, you're going to break bits, the only questions are which ones and how.

so both my posts we right!! I agree with this ^^^^^^^ and wot you write is a good summary.

but I notice no mention of white90's driving ability.

[FridgeFreezer]

What RPR said - if you haven't got lockers you'll stop with a wheel spinning and that's where a shaft will break if it's going to. Shock loads are hugely stressful on things compared to steadily applied pressure - that's why we all have hammers for removing rusted parts

You can break anything if you try hard enough.

[will_warne]

What RPR said - if you haven't got lockers you'll stop with a wheel spinning and that's where a shaft will break if it's going to. Shock loads are hugely stressful on things compared to steadily applied pressure - that's why we all have hammers for removing rusted parts

You can break anything if you try hard enough.

Well, ther's a crate of beer for you when you break your first axle component on the rebuilt truck

[geoffbeaumont]

Speaking from a position of almost total ignorance (some would drop the 'almost' ), if 'kinder' to the transmission is what you're after, would limited slip diffs not be the route to go? Or are they any better than lockers? I'm struggling to think of an example of how they'd help with the situations discussed above - for instance I don't think they'd stop the problem of a spinning wheel suddenly gaining grip.

[Turbocharger]

Nobody's mentioned the huge (static) load that appears when you turn a sharp corner on tarmac (or rock etc) with a locker engaged - could this break a shaft?

(Still ROFL @ Ali telling Tony how to drive sensibly)

[02GF74]

What RPR said - if you haven't got lockers you'll stop with a wheel spinning and that's where a shaft will break if it's going to. Shock loads are hugely stressful on things compared to steadily applied pressure -

Let's talk flywheels now and my logic is gonna be a bit woolly.... When the spinning wheel suddenly stops, as it is gripped on the tyre and not the axle, all the energy is going to be asborbed in the tyre and surface. All One end of the axles at the diff is being spun at 2 S the other suddenly stops - is that enough to twist and snap it? Can't see how else it get's broken - engine torque comes into play a little later.

Nobody's mentioned the huge (static) load that appears when you turn a sharp corner on tarmac (or rock etc) with a locker engaged - could this break a shaft?

not if they are made of elastic!!! I'd imagine in these circumstances most likley the tryres will lose grip otherwise it may. I've seen huge artics pulling 3 axled trailers (I think they are axles) go round sharp corners with the tryres losing grip.

[FridgeFreezer]

Ooop, meant to say/add:

if you haven't got lockers you'll stop with a wheel spinning and that's where a shaft will break if it's going to. If you HAVE got lockers you'll get further and then break something else in a different fashion

Another (perhaps unanswerable) question is how many breakages come from misuse of lockers, EG trying to turn with the front one in?

[jules]

mmm

I run Kam shaftes on the raer and standard on the front

I have never blown a rear sharft in 11 years of off roading

I have gone from 10 splind to 24 due everyone telling me I needed to, then when I could afford it I uprated to the Kam because I reduced the ring and pinion gearing

But I will still stand that I have never managed to blow a shaft on the rear.

But that is due to my driving stile I think and my drive train set up. the 4.2 feels like it could snap a prop with the way she can put the power down.

I dear anyone to tell me I don't push my trucks to the limit.

[Hybrid_From_Hell]

IMHO almost everyone is right here !

Do not undeerestimate what lockers do.....

They allow you to try / or continue on terrain that without them you will be stuck / stooped, and therefore it is much more difficult to break bits when you are staionary and stuck.

Therefore the lockers allow you to do more, go into and through up, down out of stuff that without them you wouldn't get near, as such as you are trying that much harder the forces involed are greater and thats why lockers break shafts etc, the terrain without lockers stops you before it all goes "BANG"

There is also the fact that lockers can protect the drive train, ie cross axled wheels spiunning, then it makes contact - BANG, with lockers you can keep moving aviod a 1000,000 rpm tyre gently then biting a root and going to 1 rpm in a nano second.

Lockers should be engaged BEFORE you are spinning everything up high RPM, shove them in if in doubt before you go into it all, that way they can aklsoi protect.

With lockers enaged, and power being transmitted though the drivetrain there is always a weak link, half shafts, and on the front CVs at angles, so yer pays yer nmoney and takes yer choice.

In answer to the Q, its YES & NO........

Nige

[RPR]

I dear anyone to tell me I don't push my trucks to the limit.

Alright dearie: You're a big girl's blouse and that's why you don't break anything. There, I've gone and done it. What now? You wanna a piece of me? Bring it on!!!!!

It's perfectly reasonable that someone could drive their Landy hard and never break a halfsaft, but I stand by my previous statement. If you use a Land Rover as God intended, you're going to break bits.

[jules]

I break loads of stuff just not shafts

Axles I have a habit of bending and I have split a supposedly unbreakable shock. M-Sport would not believe me till I posted it to them, the only ones they have broken is when WRC car had actualy crashed.

Not to mention the racers that have died end over end issues in prevous years.V8's and loads of gear boxes any 4 ird's completly spit open.

I see you and I raise you

[reads90]

Alright dearie: You're a big girl's blouse and that's why you don't break anything. There, I've gone and done it. What now? You wanna a piece of me? Bring it on!!!!!

It's perfectly reasonable that someone could drive their Landy hard and never break a halfsaft, but I stand by my previous statement. If you use a Land Rover as God intended, you're going to break bits.

As mention before

You break some bit and then replace it with big and stronger bits and then bigger tyres and then break other bits so stronger and biger bits, get your self further into the mud and get yourself even more stuck and then break things

The differance is that the bits you break are alot more expensive

I think that some case a locker with save your shafts and at times the locker will cause you to break the half shafts

Hey Turbo charger

It has taken years to prefect the art of being a complete and total ruff arse with out breaking stuff

and i think that Tonk will agree i have got it prefected