[LukeGX]

I have been checking out diff locks for a while now and I would settle on the LOKKA from 4WD Systems but for one thing: It can not be turned off manually.

I understand in 2WD with hubs unlocked the diff lock has no affect on the front wheels so the patrol should drive like a stock truck.

In offroad situations the diff lock will always be on unless the auto disengage is triggered by turning on a hard surface.

So getting to the point...

Lets say your gunning it along in some soft sand and the lokka is engaged, all is good. Then there is a big stump on one side of the track and you have to put a wheel on it, I imagine with an ARB locker you would turn the locker off just before you hit the stump to avoid excess strain on that CV as the tyre hooks into the rock. But with the lokka you can not manually turn it off.

In this situation does the Lokka disengage and allow differentiation or does it stay locked and you have to hope for the best with CVs?

 

[SpiderM]

I think no-one will have a definate answer as there are lots of variables.
That's the reason I wouldn't have one...I'm a control freak and want to have button control!

 

[azza4.2td]

From the 4WD Systems Website about the Lokka

"LOKKA will perform the same as open and LSD differentials when the vehicle is driven under equal traction conditions, ie on road. The LOKKA allows the wheels to "differentiate" around the turn, but reverses the operation in that it transfers the engine torque (hence drive) to the inside wheel, rather than the outside wheel."

This sounds like it is not "locked" all the time. But reading further, they say it is.

It also explains normal open diff operation, but basically, a open diff "drives" the outside wheel. the Lokka Drives the inside wheel allowing the outside wheel to "overtake" the inside wheel in its operation. This form of operation causes the Lokka to "drive" the slower wheel.

and below is more on it operation.

"1. LOKKA has only 4 main parts - a pair of Cam and Axle (side) gears for each axle, there are some springs and pins, some have spacers.

2. LOKKA is normally in a fully locked state and only allows differential action by unlocking the unit when the ground driven force acting on a wheel (either during turning or when negotiating obstacles) forces that wheel to turn faster than the other driven wheel.
ie a turning vehicle's wheels actually travel two different paths with the inside wheel turning in one circle while the outside wheel travels in a larger circle, and therefore faster.

3. LOKKA makes use of two distinctly different sets of opposing forces that exist due to its design - one to dynamically couple the gears when engine torque is applied and the other to uncouple the gears when one wheel overruns.

3a. The locking force is applied by the action of the pinion cross shaft acting on a uniquely designed and shaped cam - the more torque that is applied the harder the unit locks.

3b. The unlocking action occurs due to the ramping effect between the low profile ramped teeth which force the cam away from the axle (side gear) eg when an outside wheel turns faster than than an inside wheel when cornering. Power continues to be applied to the inside axle. As the turn is completed and the wheels again rotate at the same speed, the outside lock re-engages.

4. It should be understood that only when there is an external force being applied to a wheel to make it turn faster than the rest of the drive train will LOKKA allow one wheel to differentiate. Slippery surfaces where one wheel would normally break traction in an open diff cause LOKKA to stay locked - even with one or both wheels in the air, LOKKA will remain locked."

What it basically says is that when the firm road causes the outside wheel to travel faster, the diff "unlocks" by riding up a ramp, but when a wheel has loose traction, torque is applied (from the engine) to a cam on the pinion gear shaft which increases it's locking.

So basically it's where the force comes from which determines if it's locked or not. Force applied from wheel - unlocks, force from engine - locks.

So getting to the point...

Lets say your gunning it along in some soft sand and the lokka is engaged, all is good. Then there is a big stump on one side of the track and you have to put a wheel on it, I imagine with an ARB locker you would turn the locker off just before you hit the stump to avoid excess strain on that CV as the tyre hooks into the rock. But with the lokka you can not manually turn it off.

In this situation does the Lokka disengage and allow differentiation or does it stay locked and you have to hope for the best with CVs?

I would say if you had to put a wheel up a stump, the lokka will stay locked, as you are driving it. As it is already locked there is no sudden locking force, but as you come down the other side, it is likely to unlock as there may be force from the wheel as the weight of the vehicle would cause it to go faster. Either way, if one wheel is forced by the "terrain" to travel faster, it would unlock, but as soon as the other wheel speed catches up, it would relock.

I would not see too much problem with this system in the situation you suggest.

This is the website I got the info from.

4WD Systems | LOKKA Differential Locker | Gear to Goannawhere

 

[LukeGX]

Thanks, I read thier website a few times. I guess what I am trying to get to is it is known that if you are not careful with manual locking diffs (like ARB) you can break CVs.

You don't have the choice of turning off the auto locking diffs so I would hope the design of the auto locking diffs account for this somehow.

 

[Sméagol]

Breaking a CV usually occurs as a result of a spinning wheel gaining traction, which transmits too much stress through the system ,and being the weakest link the CV breaks. In your scenario unless the wheels are spinning you wont have a problem, ie you can drive with 1 side on a hard surface and 1 side on soft/ sand etc, the wheels won't be spinning because you have positive drive through the wheel on the hard surface, the wheel on the soft surface will not spin because the diff is locked therfore the wheels will rotate at the same speed.

Where you may have a problem is where both wheels are spinning and 1 suddenly gains traction, ie driving through mud etc. In this case it does not matter wether you have an air locker or and auto locker the result will be the same.

 

[Mo GU]

Had a lokka on my GU for 5 1/2years never had a problem .Lock the hubs in manual and of you go dont even have to worry about switching the lockers on and off .Airlockers are great if you can afford the readys for them .All the best with your decision mate MO

 

[LukeGX]

Where you may have a problem is where both wheels are spinning and 1 suddenly gains traction, ie driving through mud etc. In this case it does not matter wether you have an air locker or and auto locker the result will be the same.

Ahh, this is what I was getting at, So if you have an auto locker you have to be carefull of the above situation occuring whenever you are in 4WD but with manual locking diffs you only have to worry about it when the locker is engaged. (as far as damage direct form diff locks go anyway).

 

[Troyyyy]

i had a lokka ordered and paid for the last 3months and they keep saying none in stock so cancelled and airlockers are goin in as we speak

 

[the evil twin]

Breaking a CV usually occurs as a result of a spinning wheel gaining traction, which transmits too much stress through the system ,and being the weakest link the CV breaks. In your scenario unless the wheels are spinning you wont have a problem, ie you can drive with 1 side on a hard surface and 1 side on soft/ sand etc, the wheels won't be spinning because you have positive drive through the wheel on the hard surface, the wheel on the soft surface will not spin because the diff is locked therfore the wheels will rotate at the same speed.

Where you may have a problem is where both wheels are spinning and 1 suddenly gains traction, ie driving through mud etc. In this case it does not matter wether you have an air locker or and auto locker the result will be the same.

Agree totally with the "all 4 wheels spinning and 1 gets traction scenario" as that indeed puts a shock load thru the drive train on the axle that suddenly gets the traction...
BUT... thats not the only reason or scenario as the wheel's don't have to be spinning to get the torque to blow the CV.

It will also happen because with a Locker (Air or Mech) where once the wheel/s with the least traction would break and commence spinning taking the torque off the CV of the wheel/s with more traction what happens now is more and more torque is is sent to that CV and the Wheel with traction.

When the diff is locked you lose that "warning" of uneven traction of a wheel spinning up.

Think of it this way purely for illustration...
All 4 wheels on the ground and locked diffs means the engine torque is distributed approx 25% to each axle.
Lift, say, the back two wheels and left front, or put them in mud, sand or whatever, doesn't matter because now up too potentially 100% of the engine torque is going to the right front wheel until either the vehicle moves or something lets go and what lets go is the front right CV 99/100

That issue is for both air or mech lockers. It is just that mech lockers are always engaged but air are not so it "appears" to happen more to mech lockers.

The whole idea of locking is to give more controlled traction to all corners so you no longer need to rush a challenge to get the aid of momentum so if you back off a tad you shouldn't have many CV drama's. I had a LOKKA in both my prev rigs (one was a severely tweaked TD42 Turbo with very nice power figures) and had no problems with CV's as long as a bit of care is exercised.

Go at that rock climb or whatever like a bull at a gate and you'll ned a box of CV's

 

[james86]

i have had in the front of my gq for 2 years and never broken a cv i am running ntn s but not cheap $50 e bay specals now it s in my gu the only thing i dont really like bout it is when you drive it on the beach in high 4x4 the heavy steering i get over a bit but for the price compared to the air locker it works a treat its locked when you really need it has nt let me down
just make sure you have a tight lsd rear or locked rear coz im not sure what type of driving you do but when you get into harder terain if you dont have something pushing from behind ie rear locker if your not really carefullyou will breck cvs and axels every time most times they blow out through the free wheeling hub so does make a real mess

 

[adam higham]

I broke a CV not long after fitting an auto locker. But that was due to loading the front end up with one wheel in the air and coming down and the wheel grabbing traction. This will also happen if you have an air locker with the locker disengauged. The CV or the hub are generally the weakest links in the drive train and when put under to must stress/strain will break. Having the locker engauged just about guarantees that you don't break the diff itself. Good luck smashing a patrol front diff in normal conditions though anyway.

Just my 2c from experience

 

[GUWorks]

By the time you buy the Lokka, install etc and then break a CV / Axle - you have basically paid for an air locker.

I have never seen the advantage in a locker that you cannot turn on and off???

 

[badgu82]

if your to scared to run a locker and break a cv to tackle some good solid tracks buy a car... air lockers dont instantly disingauge anyways. it takes a few seconds and also backing off to disingauge... your not going to be going hard up a climb or through some mud or etc and then go "oh no i better disingauge that might break my cv" and then hit the switch! thats just plain stupid.. i have front and rear air locked and run 37's beadlocked and aired down,reduction gears,4.7 diff gears and punish mine!!! it takes some wild tracks and lots off air time and going hard to break a standard one really. either that or or incopatantcy... but given your question and some off the replys it you only want a locker for added traction and you dont really do any hard stuff and your not a twit you have nothing to worry about in the breaking cv's department... personally id rather break cv's then spit tail shafts and smash gearbox etc..

 

[sim79]

I have never seen the advantage in a locker that you cannot turn on and off???

I can, they are simpler, cheaper, steer better and rarely fail. I have seen heaps of air locker fail when they were most needed.

 

[EagleBay]

Plus once its in you just forget about it. My mate is constantly failing an obstacle, backing up locking the air locker and trying again.

 

[badgu82]

Good reply sim79 mine play up a bit. the solinoids like to bleed a bit off air now and then and the pump is always cutting in and out when they do, other times its fine!