Outer Limits 4x4 Board

hey all,

i've read a few times that people feel that a front arb will unlock quicker than a front MD, in the same situation...

so how do you come to this conclusion? because the switch light(arb) tells you?

just wondering from a design/engineering point of view..

all coments appreciated.

cheers, serg

Maxi drives do take some time to disengage, as the locking system on MD lockers is externally mounted on the axle via the locking dog. Air lockers take time to disengage as well, but release much quicker. Any diff lock under load will need to be unloaded to disengage

At least the MD lockers warning light is still illuminated til it is diengaged properly

Regards,

Trav

ARB is a high pressure setup with a stiff return on it. The maxi is a low pressure vacuum setup which makes it slower.

Slunnie wrote:ARB is a high pressure setup with a stiff return on it. The maxi is a low pressure vacuum setup which makes it slower.

The ARB locker only uses air pressure to lock the diff. The return spring is what does the unlocking. The MD locker has a detent so it stays locked until the 15psi or pressure/vacuum (I use pressure for mine) does the unlocking.

But serg has a good point - how do you know it is unlocked - because the light has gone out or because you can steer properly again?

I was under the impression that the return spring on the ARB required 85psi to activate it, assuming that the return pressure is a little less than this, it would still be a more positive action than the vacuum pressure.

ARB, I guess I don't know if its in or out by any light. Flick the switch and its usually just in or out judging by the way the vehicle acts. Sometimes it sticks when there is wind up in the axles, but its normally pretty quick. How much quicker..... dunno, and the speed of it probably makes no or little difference for consumer 4WDing as you stop, check, lock, drive, stop, unlock, watch others.

just one of those things that i think is more myth than science....

then again i don't have a front locker nor have used one, thats why i asked

from what i know the ARB uses the spring pressure to unlock and MD uses the vacuum, these both may be closer than you think... Mal said that the vacuum when unlocking equates to about 50psi

MD locking ring has a small amount of play in it.... its loose by design. ARB locking ring is a tight fit, so i would have thought that this helps the MD

you all know i'm a big fan of Maxi-Drive... but as i slowly learn more there seems to be alot of missinfomation out there...

we want fact not hersay

take trav's point for example(NOT HAVING AGO MATE) now trav's done way more 4x4ing than me so i will listen to anything he has to say..... but what does having the locking dog externaly mounted change?

imo maby its more mental than fact as the lights on MD stay on via the actuator.... so you know when its unlocked.... but switch the ARB off and its out of your mind..so to speak

cheers, Serg

thanks for your time guys

The ARB DOES disengage quicker, no not as quick as the crappy idea for ind. suggests, you can simply tell by the charecteristics of a locked diff and how the vehicle drives

By the way one of my rangies has maxi F+R and the other has a rear Maxi and front ARB, does that mean I qualify for an opinion

uninformed wrote:just one of those things that i think is more myth than science....

then again i don't have a front locker nor have used one, thats why i asked

from what i know the ARB uses the spring pressure to unlock and MD uses the vacuum, these both may be closer than you think... Mal said that the vacuum when unlocking equates to about 50psi

MD locking ring has a small amount of play in it.... its loose by design. ARB locking ring is a tight fit, so i would have thought that this helps the MD

you all know i'm a big fan of Maxi-Drive... but as i slowly learn more there seems to be alot of missinfomation out there...

we want fact not hersay

take trav's point for example(NOT HAVING AGO MATE) now trav's done way more 4x4ing than me so i will listen to anything he has to say..... but what does having the locking dog externaly mounted change?

imo maby its more mental than fact as the lights on MD stay on via the actuator.... so you know when its unlocked.... but switch the ARB off and its out of your mind..so to speak

cheers, Serg

thanks for your time guys

Serg, you've also got to question your own assumptions and work out if they're correct and if your having a go at somebody that has contibuted is justifyable and if they will bother in the future.

How does the vacuum equate to 50 psi. It either is or it isn't irrespective of it sucking or blowing. No doubt the way it happens relates back to Travs comments about the external actuator and probably through any lever action that this design uses to create the actuation. This is probably also why Mal reckons his setup generates 50psi worth of force from a vacuum setup that probably starts life as 1/4 of that. Its 50 psi at the locking dog. ARB appies that 50psi directly to the locking mechanism from the actuator (actually over 100psi), Maxi does not. Maxi low pressure system is slower to work due to less pressure and has further to travel at the actuator to gain the equiv travel which probably makes it slower again, but when its locked in, its held with 50psi of pressure.

Why does the Maxi have more play? Probably because its slow and it wont snap in/out as quickly when the pressure comes on/off the locking dog from alternate directions. That means it has more lash also, not that it'll matter.

Perhaps the milkman told me all of this and its hearsay, or I just made it all up.

uninformed wrote:we want fact not hersay

<snip>

imo maby its more mental than fact as the lights on MD stay on via the actuator.... so you know when its unlocked.... but switch the ARB off and its out of your mind..so to speak

You got the answers already.

thanks slunnie,

as i said i wasn't having a go at trav... just that what he said came of more as a statement than an explination. then again i'm a little slow to pic things up from reading.

from what i've read over time, it seems statements are more prolific than explinations.

you have explained yourself very well and this makes me think more.

i know the ARB is a good product otherwise they wouldn't dominate the market... there arn't that many sheep out there.

its easy to for people just to say it does because it does, and they may be 100% right. but that doesn't help others understand why and how.

cloughy, your a great candidate for this question, but that doesn't mean i won't listen to people "less qualified"

i'm probably the "least qualified"

cheers, serg

Speak of talking out of asses. I thought the Maxi locker worked the actuator through a pivot, but looking at the section it seems it doesn't. You can see in the actuator that it has a large volume of air that the vacuum pump needs to remove, which is probably why its slow. As for producing 50psi of force.... I don't know how it does this.



Compared to a high pressure ARB setup that drives directly onto the dog with minimal air volume, the maxi will still be slow.

Just adding my 2 cents,

The MD system follows the LR idea of illuminating a light when the difflock is actually ENGAGED. This is by far the best thing, not really important how fast it locks or unlocks, its whether it is locked or unlocked thats important isn't it?

JC

the reason for most that speed is important, i guess, is to regain the ability to control steering.

i think the harder people drive, especialy in competition this becomes more important.

always looking for the edge to gain that split against the clock

i see what you are saying slunnie and it makes sense... i have no idea how vacuum works but a spring is quite easy to understand

cheers, serg

AH. I see. Competition and ticking clocks.

I used to get so frustrated watching competitors in event prologues ambling around, I guess they hadn't realised the clock is running so they are starting right down the order every minute.

In your case then, speed is certainly important.


JC

How much difference to the locking speed would having the canister near the diff make? (yes, solenoid needed).

Does line size play much of a part in it with low level vacuum ?

justinC wrote:AH. I see. Competition and ticking clocks.

I used to get so frustrated watching competitors in event prologues ambling around, I guess they hadn't realised the clock is running so they are starting right down the order every minute.

In your case then, speed is certainly important.


JC

no im not into comps at all, would like to but $$$$$ aren't big in my pockets.

this is just a question out of curiosity..

serg

The MD system has a buffer tank with several times the volume of the actuator cylinder. Thus pump capacity has very little to do with the speed of the system.

With dash mounted Clippard valves, you do not even have to look at the light, you hear a secondary sclooouch when the piston moves and know that the dog has gone in/out.

I have very limited experience from ARBs, and it MAY be a tad faster, but I am still very fond of my MD lockers. They have operated trouble free for a couple of years now, while a lot of other components have needed attention.