Locked diffs

[Mark Whiteside]

Not lc
on vehicles with manual locking front hubs ie Suzuki sj and vitaras
Is it right that when the front hubs are locked in,the front axle is not crossed locked?
Or do i have a problem with one of the hub locks?
So does that mean in reality that when in 4 wheel drive with front hubs locked in
they are only 2 wheel drive.
i ask this question because both my boys Suzuki's only spin one front wheel

 

[Chris]

Mark, when you engage the hub locks you are simply locking each wheel to the end of the drive shaft - that drive shaft is coming out of a front diff. So no, the wheels are not cross locked. The reason for having the hub locks is generally (and note I say generally) because these vehicles do not have a proper centre diff and therefore are not happy to run continuously in 4x4. In your case, you are now in 4x4 mode, but one wheel can still spin. It is only when you fit diff locks to the front and rear diffs that the opposite wheels are cross locked. Having a center lock then means that you are diagonally locked too. It's an odd thing to explain, but 4x4s are nothing without grip. If you place 3 wheels on sheet ice and one on tarmac you will go absolutely nowhere.

if you jack one front wheel off the ground and turn it, you will feel if it's connected to anything. If it spins freely then yes, you have a hub lock problem

Chris

 

[Mark Whiteside]

Thanks Chris
nicely explained in English

 

[Chris]

No problem. Like I say - 4x4 mechanisms are not that easy to grasp when the public view is that they are something unstoppable. Reality is that a 4x4 without at least one diff lock is no better really than a normal car. OK when you have traction control and other trickery, that's different. People are often surprised at how poor their 4x4s are when they try them for the first time, expecting to look smug. What really helps is good tyres. This stops individual wheels from spinning so that the 4x4 mechanism can send drive to all of the wheels. With poor tyres on, all of the drive will go to the wheel with least grip. Which isn't helpful!

Glad we could help


Chris

 

[Mark Whiteside]

So then Chris
An import 80 with a LSD
in extreme conditions( like you said on ice)
An LSD is pretty useless then

 

[Dave Docwra]

Hi Mark, An LSD is better than an open diff, but not as good as a full diff lock, you would be suprised how effective they are when working correctly.

 

[Mark Whiteside]

so then
whats the different between an LSD and and open diff
or what i am trying to say how does an LSD work
i do understand how a open diff works



traction control
am i right in thinking that it works by braking the wheel/wheels with the least friction
so i am right in thinking in extreme conditions again it would not be very good

 

[Jon Wildsmith]

a (working) LSD only allows limited speed difference between the two wheels on the axle, so as one wheel spins it will start to engage the LSD mechanism (there are different sorts) which transfers some of the torque to the other wheel. Active traction control (as apposed to just ordinary traction control that usually only has control over engine output) applies the brakes to the spinning wheel so that torque is transfered to the other one. Given that the wheel was spinning and not providing any traction in the first place you don't really lose anything by having it braked. Where you do lose out is that it takes time for the system to work out what's happening, apply brakes for a short length of time, see what happens when they're released again etc so it's good for surfaces where the traction only goes away for a short time but not su good for a long mud run where you do start to run out of steam.

 

[Mark Whiteside]

a (working) LSD only allows limited speed difference between the two wheels on the axle, so as one wheel spins it will start to engage the LSD mechanism (there are different sorts) which transfers some of the torque to the other wheel.


so then a working LSD you should have drive to both wheels
or what im trying to say is that if one wheel was lifted off the floor you should have some drive to the other wheel
or if not how would you diagnose a LSD inop

interesting stuff

 

[Chris]

You're about there Mark. The LSD typically works on some friction plates inside the diff which has to have special LSD oil in there. The two wheels always have drive as long as they are on a surface with grip - as we've explained. When you lift a wheel or lose grip, the split as I understand is is around 80 - 20 or thereabouts. So the wheel with grip doesn't get full drive. As has been said, in good condition that really can be surprisingly effective, but I did read that they are generally only good for about 50k miles before they wear out. It depends how many corners they've been around!

If you jack one wheel up you should be able to feel the resistance of the LSD when you turn the wheel. Not very scientific, but if it is hard to turn, then that's how much grip you are getting to the wheel that's on good ground. If it spins easily then it probably 'out to lunch'.

Chris

 

[TonyP]

Great thread.... never knew LSD's worked. Thanks

 

[Jon Wildsmith]

or what im trying to say is that if one wheel was lifted off the floor you should have some drive to the other wheel
or if not how would you diagnose a LSD inop

With one wheel lifted a working LSD should try to drive it off the jack yes I have no personal experience of a LSD but I'm not sure you'll feel any difference just turning the wheel back and forth, I think it takes a bigger and more sustained spinning of the wheel to engage the LSD bit? From reading on the net it sounds like they're often worn out by the time owners who are actually interested in them get the truck!

 

[Chris]

I have tried it on a Hilux Jon and you can feel the drag for sure.

C

 

[Jon Wildsmith]

I have tried it on a Hilux Jon and you can feel the drag for sure.

That's useful to know, I didn't think they engaged that easily. A working LSD should be quite a handy thing to have then.

 

[Dave Docwra]

Mine has done 120k miles & to my suprise both LSDs are still working, Some time back I was in a Mud hole of a pay & play place between Milton Keynes & Bletchley & on the day I could not understand why I had so much traction & was getting through areas where discovery's were struggling, I also had very worn tyres, I checked & found I had LSD diffs fitted & since then I have tried the simple test of jacking up one side of the vehicle & gently trying to drive forward to which the vehicle was very keen to do.

One thing I did notice, was whilst it was jacked up it was doing the same as Chris has said, the wheel's felt like they were binding & the faster you tried spinning it by hand the heavier it got.

 

[Chris]

Dave, you beat me to it. Yes, the faster you try to turn the wheel, the more you could feel it. Very slow turns gave no particular feedback at all. Now my mate's Lux is pretty shagged.(It's for sale by the way ) and I don't think he's got my LSD left. His new one has a locker - shocker!

C

 

[Mark Whiteside]

Thanks guys
very helpful as always

 

[Ben]

Mark, when you engage the hub locks you are simply locking each wheel to the end of the drive shaft - that drive shaft is coming out of a front diff. So no, the wheels are not cross locked. The reason for having the hub locks is generally (and note I say generally) because these vehicles do not have a proper centre diff and therefore are not happy to run continuously in 4x4. In your case, you are now in 4x4 mode, but one wheel can still spin. It is only when you fit diff locks to the front and rear diffs that the opposite wheels are cross locked. Having a center lock then means that you are diagonally locked too. It's an odd thing to explain, but 4x4s are nothing without grip. If you place 3 wheels on sheet ice and one on tarmac you will go absolutely nowhere.

if you jack one front wheel off the ground and turn it, you will feel if it's connected to anything. If it spins freely then yes, you have a hub lock problem

Chris

No problem. Like I say - 4x4 mechanisms are not that easy to grasp when the public view is that they are something unstoppable. Reality is that a 4x4 without at least one diff lock is no better really than a normal car. OK when you have traction control and other trickery, that's different. People are often surprised at how poor their 4x4s are when they try them for the first time, expecting to look smug. What really helps is good tyres. This stops individual wheels from spinning so that the 4x4 mechanism can send drive to all of the wheels. With poor tyres on, all of the drive will go to the wheel with least grip. Which isn't helpful!

Glad we could help


Chris

part time 4x4's such as suzuki 4x4s, daihatsui 4x4s, and certain toyota 4x4's like my LJ70 and my mates hi-lux dont have centre diff locks because there not full time 4x4 and therefore dont need a centre diff lock.

when a part time 4x4 vehicle is put into 4 wheel drive, the power is split to the front and back wheels, and is in effect locked just like a centre difflock. thats why using part time 4x4's, in 4 wheel drive on dry roads results in transmission wind up because the power cant slip out any where as the drive is equal and constant front to back.

i hope that makes sense.

 

[Chris]

Ben, I was avoiding that issue in case it offended anyone - the reality is that vehicles that have these front FWHs do so because the manufacturer have cheapened off the design and haven't fitted a proper centre diff. Therefore they HAVE to have locking hubs to avoid the major problems that not having a CD brings. But I don't think that it's the case that all of them actually act as a locked centre diff. They are still open, but quite crude in design. I know - I drove a Freelander once!!!!

How's the wooden bumper coming along?

Chris

 

[Ben]

Chris, no offence received, i just think youve got it slightly wrong.

they dont have to have front locking hubs!

suzuki 4x4's come with either fixed locked hubs, manual locking hubs, or automatic locking hubs.

they will work perfectly fine with the hubs locked in 2 wheel drive, and wont wind the transmission up. the only reason the manufacturer fitted free wheeling hubs is to improve fuel economy, by reducing the drag of the front drive terrain constantly turning.

i may be wrong but i think freeloaders are a different setup to most other part time 4x4's.

dont get me wrong, having an 80 series which is full time 4x4 with 3 locking diffs is defiantly a lot better, i was just trying to explain that a centre diff lock isnt neccesary on part time 4x4 vehicles as it essentially already has one.