Tip # 57 By Request: Diff-Locks, the Two Types, Advantages and Dangers!

Submitted: Friday, Aug 05, 2005 at 23:18
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For those of you in the “Planning Stage” there are two basic types of Diff-Locks, and that is what this Tip is about… Pros and cons of the two…And a follow up to Tip # 55 on Off-Road Towing... As there is a very serious danger involved.. Being and enthusiast I have owned both extensively, so here goes…

Part of this comes from how to use your Diff Locks in
Bushtracker Tip # 16, Extreme 4x4 - Diff locks priorities, and then I move on to practical use of them and a danger involved.... (I digress a moment for those that don't know what Diff-locks are....) This is the differential locking device that locks up both wheels evenly like a tractor... Without it, most 4x4's will just transfer the power through the differential to the least loaded side (and the one that is in the bog just spins while the other on firm ground just sits there doing nothing) Ha! Now a differential is necessary to allow your drive axles to go around curves so the outside wheel can turn more than the inside.... However, it makes most 4x4's in the mud only sort of have one wheel driving in front and one in the back, if two of the wheels are slipping you have nothing and "Bogged" again... Each differential with a diff-lock engaged increases your 4x4 ability by about 25% in the right conditions…

One style of Diff-Lock is like the “Detroit Locker”, and it is engaged all the time, to mechanically disengage itself as necessary… Now that is OK, one type drives a little funny and clicks as it disengages while you go around corners, and the Japanese one in the larger trucks, gives a funny little lurch now and then in town when it disengages, sort of a feeling like you ran over a little bump with one wheel… But that is not the problem.. The problem is that it pretty much stays on except when you go around corners, and you cannot manually disconnect it !! Believe it or not, there are some times when Diff-Locks are a disadvantage, particularly when you are slipping sideways on greasy ground, loosing traction on a steep slope side on down a hill… I first learned this in about 1973 trying to get along a steep slope to pick up a load of firewood I had cut… I could not disconnect a diff-lock, and the even traction was a disadvantage… I went sideways more than forward.

With the other type of Diff-Lock, like the one ARB makes, it is operated by air. I bought electric Diff-Locks for my 1993 Troopcarrier out of a Sahara, but they both have one thing in common, you select when you want them in, and select to disconnect them… The ARB ones have the added advantage of being run by a compressor, that you can buy a hose for, to fill your tyres. The point is that in the same situation as above, sometimes in funny circumstance you are better off not having a Diff-Lock engaged… Believe me, it happens..

Now here is a "Safety Warning"…. On my 100 Series, I have the ultimate: Diff-Locks front and rear... But that takes talent to drive, as in the mud with both wheels turning and biting in the front, if one wheel grabs some firm ground it will lurch and over-steer in that direction... Let me emphasize that point!!!! In off road conditions, the front Diff-Lock is the greatest, but you have to learn how to gingerly drive it or you will hit a tree.... With both wheels evenly grabbing mud it is fine; but as one gets a hold of some serious traction it will lurch severely and pull the front end that way and oversteer... You have to take it slow and careful... But I have to tell you that with all four locked up, my 100 Series Cruiser will darn near tow another Cruiser where it could not go by itself with standard slipping differentials.... It is a real Beast! Just know that in most conditions, you would not run down a greasy track with the front Locker engaged... And if you did you have to be really careful as the one side can catch serious tracktion and oversteer lurch to one side a metre or two.. OK?

The important thing to remember is to drive very slowly with the front locker engaged, as it will feel just fine if everything is nice and greasy, but you will tend to build speed, but when you hit a firm spot with one wheel and it will scare Hell right out of you. It can be dangerous if you have much speed on, as it really can jump sideways a couple of meters… You don’t want to get to overconfident, building speed, to have that happen; or you will find yourself having a close encounter with a tree or ditch before you know what happens..

Also when getting into the poo, and you sense “this is trouble”: Keep something in reserve, or you will find that you ran into trouble with all capabilities already running, and nothing in reserve to get you back out. One of the greatest things about Diff-Locks is to get you OUT of trouble… If you use them liberally all the time, guess what, they will get you further INTO trouble with no reserves to get out.. The one sort of exception that comes to mind is the big 20 metre bogs in the track…. For example: You can see where you are going, dry ahead through a 50-60 foot muddy bog, and it is ALL OR NOTHING. So, a little run at it and Diff-Locks engaged, and a good gear maybe third in low range (depending on the tow vehicle), and power on through it without hesitation.. But in unknown messy ground, in general, save the Lockers to get you out if you run into trouble rather than using the Lockers to get you further into the BOG…!

Additional trick: (For older Cruisers and Patrols, and some other vehicles)
I have had two of my own Cruisers in twenty years with front and rear Diff-Locks in 4x4 Clubs, and where they will go is awesome! I still have one… Plus I have the old 1989 Sahara with another trick combo that I have fully restored for my Son. It came with an LSD (Limited Slip Diff) in the rear. They do not last long as clutch pack discs LSD, but you can rebuild them with a spacer and bigger spring to get an excellent over performance LSD, and it will not wear out fast if you put it in the front on a vehicle with “Free wheeling hubs” as it is not turning on the highway. (In the older Cruisers the front and rear diffs were interchangeable). In those conditions it really gets no wear, only in 4x4 with the hubs engaged. So on my old fully restored 89 Sahara Turbo, I have an ARB Locker in the rear, and a custom built LSD in the front, that used to be the rear one. On the older 4x4’s the diffs front and rear were interchangeable. So it is now almost as good as having twin ARB Air Lockers ! What a difference it makes, you can crawl over things that lift a wheel off the ground front or rear or both and still keep going… Really almost doubles the traction over a normal 4x4 in the right Conditions…

Cheers from the Ranger, Still doin’ it in the Bush…….

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