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Aussie Locker - how does it work?

sureshot007

NAXJA Forum User
Location
Kenmore, NY
I wasn't sure where to ask this question, so if there is a better forum, feel free to move the thread.

I have been trying to figure out if an Aussie Locker (or similar style) will work for me. The reading I've done says that it will automatically unlock when one wheel is turning faster than another, ie street driving and turning. What exactly makes it unlock? If it does unlock in a turn, and I stomp on the gas, will it lock up again?
 
You can think about it as similar to a socket and ratchet. Hold the ratchet in one hand and the socket in the other hand, the ratchet represents the driveline and the socket represents the wheel. If you turn the ratchet the socket has to turn in that direction, but if you turn the socket in the same direction it will click and spin ahead. Exactly the same thing happens in an automatic locker (Aussie, Lockright, Detroit, etc) on each side. The center pin in the diff puts pressure against the side gears of the locker putting outward pressure that forces the dog teeth to stay engaged and the locker locks both axles together. Under light to moderate throttle as long as the wheel trying to spin ahead puts more force back against the side gear than the center pin puts against the side gear then that one side will unlock and that side wheel will spin ahead freely while cornering. If lots of throttle is applied it will lock up.

The unique driving characteristics of an auto locker are because only the inside wheel is getting power around corners, which can feel like a push around corners sometimes or a wiggle in the rear when changing cornering directions on a winding road since the driving wheel keeps changing sides.

Sometimes there is a tire chirp when starting out around a corner, like from a stop sign and making a right hand turn. The tire chirp is because only that inside tire is getting power, the weight is transferring to the outside removing weight from that tire, and a little too much throttle is applied casing that tire to spin until it catches up with the unlocked outside tire and the dog teeth side gears engage again, then the outside tire spins ahead again, the inside tire chirps to catch up, etc, etc, and you ge that chirp chirp of tire spin. If you can be a touch easier on the throttle it won't chirp, or if you really mash the throttle then the locker will stay locked and you'll just get tire spin.
 
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Yes it will lock up. Basically you have side gears attached to each axle shaft. In between those are 2 more pieces with teeth that engage the side gears but springs keep them separated from the side gears so the teeth aren't engaged when you are off the gas.
The 2 middle pieces have an ovaled hole that the cross pin goes through. When you hit the gas the cross pin rides up on the ovaled hole and causes the middle pieces to overcome the springs and engage the side gears. At this point you are locked. As soon as you let of the gas the springs come back into effect and disenage the middle pieces from teh side gears.

^^ looks like we were posting at the same time
 
The unique driving characteristics of an auto locker are because only the inside wheel is getting power around corners, which can feel like a push around corners sometimes or a wiggle in the rear when changing cornering directions on a winding road since the driving wheel keeps changing sides.

This is the specific circumstance that I am curious about. I'm building my new rally truck (2wd XJ), and I'll be racing down twisty roads on loose surfaces. I'm trying to decide if it will be better to weld the diff or pick up a cheap automatic locker. The downside to welding is that I have to drive the truck on the streets between stages. I need something that is very predictable. Sounds like an automatic locker is not going to work for me. Am I wrong?
 
I got a Rear Aussie about a month an a half ago and I love it. I had the same questions and uneasy feeling that you have about getting a automatic locker. I am VERY happy with my Aussie locker.

I use the jeep as a daily driver in the winter and take out out to Rausch during rest of the year. By daily driver I mean everything from city driving (White Plains, NY) to Highway speed up to 70-75. As far as drivablity, I really don't notice a huge difference at all, other than a light clicking around turns. My wife is very picky when the jeep makes funny noises (but all jeeps do). I don't think she has even really noticed the clicking over the radio.

To simplify how it works, as you go around a sharp right hand turn, the outside wheel will be turning faster than the inside wheel. The locker will unlock and ratchet for the difference in speed, thereby preventing your tires from chirping.

But what about when I'm taking off from a light.. and turning right.. all while going up a hill??? Well that is about the worst case on-road scenario that I could think of. From my personal experience with the Aussie, I have to say that as long as you are not mashing the gas, the locker WILL STILL unlock and ratchet. If you hit the gas and send enough torque to the rear wheels, it will remain locked and chirp on you. I have NEVER had the rear wheels chip on me during the course of normal driving. I have tested to see if I could get it to not unlock and chirp around a corner, with just enough gas it will. The margin that you have there is very reasonable.. aka. drive like a normal responsible adult.

What exactly makes it unlock?
The hole for the cross-pin is slightly elongated so when torque is applied it holds the locker in the already locked position. Without enough torque on the locker, in a turning situation, you will be able to to overcome the spring tension with the faster wheel and the locker will open for split second by ratcheting to the next tooth.

If it does unlock in a turn, and I stomp on the gas, will it lock up again?
Absolutely YES.

Sorry that was long. Hope that helps.
 
It just does.

Oh wait, that's the posi-trac rear end on a Plymouth.
 
This is the specific circumstance that I am curious about. I'm building my new rally truck (2wd XJ), and I'll be racing down twisty roads on loose surfaces. I'm trying to decide if it will be better to weld the diff or pick up a cheap automatic locker. The downside to welding is that I have to drive the truck on the streets between stages. I need something that is very predictable. Sounds like an automatic locker is not going to work for me. Am I wrong?

For the purpose described,I say p/u a Trac-Loc(factory posi) and rebuild it with an up-graded spring/clutch pack.
 
Welding it will give you poor drivability on the street and make it very loose under rally conditions. You are much better off with a locker.
Welded = loose under rally conditions? How would a locker be any better, since it would "lock" under rally conditions?


For the purpose described,I say p/u a Trac-Loc(factory posi) and rebuild it with an up-graded spring/clutch pack.
I have a trac-lok in the comanche, and I'm not all the impressed with it. It would cost me the same to get a trac-lok as it would an aussie locker (while it's free to weld it).
 
Welded = loose under rally conditions? How would a locker be any better, since it would "lock" under rally conditions?
Unless you're hard enough on the throttle to spin a tire you will have differentiation and therefore not slide excessively. At speed the stock engine does not have the power to keep the wheels under alot of torque all the time. Under acceleration you will be locked, at cruise speed you will have a differential action.
 
I have been DD'ing my XJ for about 2 months now since I did the 8.8 swap with a Lockright. As far as I know the Lockright works the same as the Assuie... My XJ also has the AX15 and believe me you will definitely notice that the locker is back there if your driving a manual.

My shifts seem "harder" and I have noticeable... I guess the term is "torque steer" when I shift fast while getting on it (the whole jeep jerks sideways a little). Also, when coasting through a tight turn with the rpms up high enough (like after downshifting into a turn) there seems to be enough resistance/torque in the drive line to cause the locker to lock-unlock rapidly. This causes the jeep to jerk loudly as the slop in the drive line is allowed to load and unload quickly. My remedy for this is to simply just push in the clutch, coast through in neutral, or just don't downshift and stay in a higher gear.

Anyways my point is that from my experience, installing an automatic locker will have more of an impact on your driving style with a manual trans, as opposed to an auto.
 
This is the specific circumstance that I am curious about. I'm building my new rally truck (2wd XJ), and I'll be racing down twisty roads on loose surfaces. I'm trying to decide if it will be better to weld the diff or pick up a cheap automatic locker. The downside to welding is that I have to drive the truck on the streets between stages. I need something that is very predictable. Sounds like an automatic locker is not going to work for me. Am I wrong?


The spool and the locker would work the same on a loose surface under power, so it won't make a difference. The locker will differentiate around a corner with little power. The locker will differentiate on the pavement. Depends on what's important to you. I don't know about rallying, but plenty of desert race trucks run spools in the back. But, desert race trucks don't depend on going fast around corners. I think on a fast corner under power on dirt the locker, the spool, and the limited slip will all spin both tires, so what you want in the other situations should probably determine what you do.

Right now I'm doing a basic set up on an XJ for rallycross, which is different from rallying, and the customer wants the rear end open but he's running 4wd.

BTW, all automatic lockers work the same, Detroit, Aussie, Lockright, etc.
 
Personally, there is no way I'd ever want an open diff on the rear of anything 4wd/awd. There is a misconception that it reduces understeer.


From what perspective? Road racing? Dirt racing? Rock racing?

I love my open rear diff in the buggy, wouldn't want it any other way. But that's another subject. In rallycross the turns are likely tighter and slower than in most of rally racing, so slightly different handling issues. It seems like in rally racing you want the rear to kick out as you power around corners, so a locked or spooled rear diff would be fine. In rallycross you have to stay between the cones in tight corners so keeping the rear in line could be more important.
 
It all depends on the course. If you have enough room and speed, you can just flick the car to get it sideways and modulate the gas to rotate it. If you find that you don't have enough room to do that, then you just add a bunch of toe out in the rear and it will rotate all on its own (but don't use that setup for anything faster than 2nd gear courses, because it gets sketchy at higher speeds).

Moral of the story, it's my personal experience that most people don't toss the car enough at rallyx to get it to move the way they want. Most of my rallyx experience is with Subarus, and and STI with an LSD front/rear and the center diff locked is just a beast...but you really need to know how to drive it.
 
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