diver_matt

That last thread I found was about 6 months old and didn't want my question to be 7 pages into it. Read all the posts and some were very informative. I'm considering doing a single locker in the rear with gears or doing gears and trutrac front and rear. Most have said to go with Aussie up front, though. Couple questions:


An aussie would lock both in if a tire slips but, it slipped for a reason. That doesn't mean the tire that slipped will actually gain traction, right? Example: A tire is slipping on a wet rock. The aussie locks them but the wet rock is still just as slippery. So while both might turn together, it doesn't mean the slipping tire is actually gripping the surface. If it's not, then what's the point of sending power to that tire?

Same scenario but with a trutrac. The spinning tire would get less power. Therefore, the side with traction has more power available to push over/through the obstacle, right? Having this in the front and rear sounds like a great idea.

I'd LOVE to hear from actual experiences or industry professionals. Thanks!!

Dynatrac

Think of a time where a rig with open diffs has two tires spinning and the rig isn't moving. Frequently, this is on a hill where one front tire is in a hole spinning and the opposite side tire on the rear is also in a hole spinning. The tires not in the hole have traction but no power is being transmitted to those tires. In an open diff the power is transmitted to the axle with the least traction coefficient. The hole is your 'slippery rock'.

In the case of a locker, equal torque is sent to both sides. This means that the tire not in hole can provide torque to move the vehicle. Both tires are provided equal torque and the tire on the ground has sufficient torque to move the vehicle.

In the case of a Truetrac LSD, the amount of torque transferred is determined by the bias ratio designed into the devise. A Truetrac has a bias ratio of about 3-1. This means that up to nearly 3 times the torque available to the spinning tire can be pushed over to the tire with traction. A tire in the air has zero torque available so zero torque (3x0=0) will be sent to the other side. If the tire in the hole, despite spinning, is generating 75 lbs of torque (friction) then 225lbs (3x75=225) will be sent to the other side. Usually this extra torque will help the vehicle move but not in every case. Frequently adding braking will provide additional resistance which the differential senses as torque. This causes more torque to be sent to the side with traction.

In the case of a factory Trac-Loc LSD which wears out over time ands has a bias ratio of less than 2-1 new, the example shown above would only generate 150lbs (in perfect condition) of torque to the side with traction. Obviously, this difference is frequently the difference between moving and stuck.

In your example, you're talking about the slippery rock. It's not the slippery rock that is the variable, it's the other side and what it can do to help move the vehicle. You're right, slipping is slipping- but if the other side doesn't receive torque to move the vehicle, you're stuck.

porters

Since you are in California you probably don't have a lot of ice to deal with as that is where the disadvantage of the Aussie lies. For anyone else reading the thread considering an Aussie, they can be dangerous on ice as ice does not provide enough traction to unlock the Aussie in corners. When the Aussie can't unlock the tires push through turns breaking traction and instead of turning you go straight. Aussies are not recommended for front diff application in icy areas.

mkjeep

Aussie is a great cheap way to lock the front. I'm about done with mine though. When I change my front axle, i'm going selectable up front, it makes it hard on switchbacks and tight turns with an auto locker in front. Great for wide open crawling though. I do love my detroit in the rear though.

Dynatrac

There is no perfect system. A selectable locked is harder to steer than an auto locker. The JK doesn't have the best power steering system and its flaws show up pretty quick with a locker up front with a hard packed surface. It's a good idea to address your steering by going to a ram assist. I also like 2WD low range kits to help you get the gear reduction but no 4WD. In a perfect world we'd all have t-cases with twin sticks like an Atlas. Being able to have 2 lo front or 2 lo rear is a big advantage.

diver_matt

I've read all about the auto locker in icy conditions. Thing is, I am planning on doing some snowboarding in the winter and probably every winter thereafter. That's why I'm leaning to the truetrac front and rear or just a locker (Detroit) rear. Based on the explanation provided, it certainly seems truetrac is more what I need than two fully locked axles.

Only remaining concern....just how sensitive is the detroit locker in the rear? In "Lockers 101" it says even a slight variance in tire diameter can throw it off. Slight meaning a couple psi? 10 psi? I don't want to have to worry about that constantly or when airing down. ??? Thanks!!

nthinuf

A TrueTrac front, Detroit rear combo would work out great for you. You'll get used to the quirks of a rear autolocker fairly quickly, and I would imagine that you won't be on ice more than a few times, and for fairly short time periods, each season. I ran this combo for almost 10 years and really liked it.

I actually started with front/rear detroits, but spent too much time on icy roads and freeways up in the mountains, so swapped the TT in up front. A pair of TT's would have fit my needs better, as I don't spend a lot of time in the rocks, but the rear auto wasn't nearly as bad as the front.


I think that caution is more for a situation like having a brand new tire, and one with 30% tread left, on the same axle. I rotated every 3k, keeping the tire heights on each axle as close as I could, and never had an issue with it.

mkjeep

I haven't tested it , but a couple psi or so won't throw it off, 10 maybe , but not just a few. One way to make sure is to measure both tires and if one is worn a good bit more, you'd have to add more air to that tire. (Ex. if you have a spare thats worn down way more than the other tires.) Thats really the least of your worry with owning a Detroit.