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Discussion Starter · #1 ·
Final step.....Close to pulling the trigger on re-gearing my 2015 JKU Sport from its 3.21 to 4.56. The only remaining choice to be made is between Eaton Tru Tracs and Lockers. I drive my rig daily to/from work and occasionally off-roading other than rock crawling.

Based on the merits of each of those products and advice I have received so far, it makes sense to use Tru Trac on Dana 30 in the front and the E-locker on the Dana 44 in the back.

Questions:

1) For those that have switchable lockers in the front, is it hard to turn with them on? Any other issues especially in snow/ice?

2) For those with Eaton Detroit Tru Tracs in the front, any issues, especially in snow/ice?

3) Any major downside on the configuration choice I am making?

Please share any input and/or videos you might have of how each of these behave.

Absent any significant observation anyone shares, I am going with the above mentioned set up end of this month.

Thanks in advance.
 

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A more practical setup (if you want both a TrueTrac and an e locker) is TrueTrac in the rear so that you're always taking advantage of it, and e locker in the front when you need extra help climbing up something off road in 4WD.

TrueTrac both front and rear would probably be more effective for street driving in snowy conditions in 4WD. E locker up from leans more toward pure off road capability.
 

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A more practical setup (if you want both a TrueTrac and an e locker) is TrueTrac in the rear so that you're always taking advantage of it, and e locker in the front when you need extra help climbing up something off road in 4WD. TrueTrac both front and rear would probably be more effective for street driving in snowy conditions in 4WD. E locker up from leans more toward pure off road capability.
Totally agree. e locker up front TrueTrac rear.
That being said a locker is useless onroad, period! Off road in deep snow, awesome.
 

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Discussion Starter · #4 ·
I understand what both of you are saying.

My logic for the set up I was proposing was based on two concerns:

1) Dana 30 in the front may not be able to handle lockers all that well.

2) Its hard to steer with lockers on.

As such, with true trac it remains "open" until one of the wheels slips.

How do you see these concerns? Opinions/experiences?
 

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I have a friend who is running the true Trac in front and rear and loves them...probably what I'm going to do since I don't hard core off road
 

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I understand what both of you are saying. My logic for the set up I was proposing was based on two concerns: 1) Dana 30 in the front may not be able to handle lockers all that well. 2) Its hard to steer with lockers on. As such, with true trac it remains "open" until one of the wheels slips. How do you see these concerns? Opinions/experiences?
I hear you about the D30 and lockers. However, when it comes to snow rear locker is useless and downright dangerous onroad, whereas rear TruTrac (LSD) is more stable on and off-road. Front locker also useless and dangerous in snow onroad, however, off-road in deep snow it will pull you through.
The problem with a LSD front on slippery roads is it will auto lock when it senses on wheel spinning faster then the other. This could happen while you are Cornering which would cause a 4wheel drift and in the weeds you go. A locker is always open unless activated.
 

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Discussion Starter · #7 ·
All helpful point...

What I am inclined to conclude now is that I've never had an issue with traction even in our Chicago snowy weather. When I start to, switching to 4WD addresses it adequately.

So, I am thinking I don't have a problem "ON ROAD" that I need Tru Trac to fix.

That said, really what we are talking about it increasing capability OFF ROAD.

What is best for off road? I think selectable lockers front and rear.

Also, Tru Trac when on a hill or rocks won't be helpful until one of the wheels slips for the other to engage. With lockers, I can generate that extra pull and push if needed, until when stay in open diffs.

So may be I should just get lockers both front and rear. this way, they can be turned on when needed.
 

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I have Tru Tracs front and rear. Can't speak about lockers, I've never had them.

I like the Tru Tracs a lot. Just point and go, never worry about locking or not, great in snow and offroad, and don't have to worry too much about my front D30. Half the cost of true lockers, and never need to worry about air, airlines, or power cables. No worries about water/mud getting in from said lines and cables, either.

And I keep up pretty well with the guys who are locked on the trails, too.
 

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The problem with a LSD front on slippery roads is it will auto lock when it senses on wheel spinning faster then the other. This could happen while you are Cornering which would cause a 4wheel drift and in the weeds you go.
This is incorrect, at least for the TrueTrac style LSD. The TrueTrac is an input torque based LSD, not wheel speed differential based. It doesn't "auto lock" when one wheel spins faster than the other. It basically has an internal frictional force that tries to keep the two sides spinning the same speed, but this internal force is proportional to how much torque can be applied from the driveshaft, through the diff and wheels to the ground.

Basically, the harder you try to accelerate (with adequate traction to support the acceleration), the harder the TrueTrac will work to keep the two wheels spinning the same speed. Driving responsibly in snow will not cause sudden dangerous "lock up", because you'll be driving gently. Hammer the throttle, though, and you'll definitely get into a full 4 wheel drift more easily than with open diffs.


A speed differential based LSD would definitely cause problems in the front, even in 2WD. Even torque based clutch pack LSD (like factory rear LSD) can cause problems in the front in 2WD, because they are usually preloaded to resist speed differential even when there's no input torque.
 

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Question to the OP. I am in the same position as you (3.21 need to re-gear to 4.56).

My question is have you already considered the Auburn Ected Max which is both an LSD and an electric locker? Perhaps you have decided already decided against it. Just curious what your selection process was to narrow down your options to the TruTrac and and the Eaton e-locker.
 

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Discussion Starter · #11 ·
Decision made: going with a Tru Trac front and rear with re-geared to 4.56. While the differential is going to be operated on, save on labor and add on improved traction mechanism. Tru Trac is ideal for me for its low maintenance and lock when needed characteristics in all weather and light/moderate off roading.

Here are some of my reasons.

My shortlist of Eaton products was based on the most positive and reliable history of performance coupled with the simplicity of the device and maintenance free aspects of it. Lots of research including wheeler and installers.

Key points for deciding that I researched quite a bit, consulted experienced wheeling friends, installers, etc.


1) The Jeep currently powers equally both left/right wheel on the engaged axel until one slips, when only the slipping wheel gets all the power (http://www.youtube.com/watch?v=yxHQeO-Y7GU).

2) e--Lockers rear or front increase the turning radius for sure and have to be dis-engaged after getting unstuck,

3) they are mostly useful for straight on driving when stuck,

4) Tru Trac DOES not use a clutch that wears down quick, instead it uses helical gears (better),

5) TT DOES NOT need more than a fraction of a second's worth slippage on one wheel for the other one to lock on and kick in,

6) TT is not bad in snow/ice unless you are going at high speeds, which contradicts safe driving in slippery conditions to begin with, thus not likely,

7) e-lockers require drilling a hole into the differential, even though sealed, its still one more thing to check up on,

8) e-lockers cost about $1200 more than TT,

9) I do not like rock crawling....which is the only thing TT sucks at...that's OK,

10) TT basically is totally automatic and maintenance free that locks in when needed and open when not,

11) the up hill scenario where stuck half way, when in 4LO, ALL 4 Jeep wheels are powered, unless one or two are slipping....within a fraction of a second, the other one will lock on and increase traction to keep climbing,

12) it won't be making a wheel spin divot losing momentum much at all before the other side locks on and lets you move up......

SO, unless one does rock crawling, TT is the best thing to get.....getting 4.56 gears and TT by Eaton (Detroit)....deposit on the job is going in tomorrow....last night to change my mind ....LOL...but been very thorough concluding based on the merits of what I have and want.


Also, its about the Return on Investment too....I sure could get an iron clad unstuck insurance policy with a locker, but for that rare scenario where TT does not work, i.e. one wheel is up in the air, not worth spending an additional 1200. ROI is important. I could use that money for the big brake kit or something else....LOL....thank you all!!
 
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Decision made: going with a Tru Trac front and rear with re-geared to 4.56. While the differential is going to be operated on, save on labor and add on improved traction mechanism. Tru Trac is ideal for me for its low maintenance and lock when needed characteristics in all weather and light/moderate off roading.

Here are some of my reasons.

My shortlist of Eaton products was based on the most positive and reliable history of performance coupled with the simplicity of the device and maintenance free aspects of it. Lots of research including wheeler and installers.

Key points for deciding that I researched quite a bit, consulted experienced wheeling friends, installers, etc.


1) The Jeep currently powers equally both left/right wheel on the engaged axel until one slips, when only the slipping wheel gets all the power (http://www.youtube.com/watch?v=yxHQeO-Y7GU).

2) e--Lockers rear or front increase the turning radius for sure and have to be dis-engaged after getting unstuck,

3) they are mostly useful for straight on driving when stuck,

4) Tru Trac DOES not use a clutch that wears down quick, instead it uses helical gears (better),

5) TT DOES NOT need more than a fraction of a second's worth slippage on one wheel for the other one to lock on and kick in,

6) TT is not bad in snow/ice unless you are going at high speeds, which contradicts safe driving in slippery conditions to begin with, thus not likely,

7) e-lockers require drilling a hole into the differential, even though sealed, its still one more thing to check up on,

8) e-lockers cost about $1200 more than TT,

9) I do not like rock crawling....which is the only thing TT sucks at...that's OK,

10) TT basically is totally automatic and maintenance free that locks in when needed and open when not,

11) the up hill scenario where stuck half way, when in 4LO, ALL 4 Jeep wheels are powered, unless one or two are slipping....within a fraction of a second, the other one will lock on and increase traction to keep climbing,

12) it won't be making a wheel spin divot losing momentum much at all before the other side locks on and lets you move up......

SO, unless one does rock crawling, TT is the best thing to get.....getting 4.56 gears and TT by Eaton (Detroit)....deposit on the job is going in tomorrow....last night to change my mind ....LOL...but been very thorough concluding based on the merits of what I have and want.


Also, its about the Return on Investment too....I sure could get an iron clad unstuck insurance policy with a locker, but for that rare scenario where TT does not work, i.e. one wheel is up in the air, not worth spending an additional 1200. ROI is important. I could use that money for the big brake kit or something else....LOL....thank you all!!
Wow, both well researched and articulated. I appreciate it.
Thank you.
 

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5) TT DOES NOT need more than a fraction of a second's worth slippage on one wheel for the other one to lock on and kick in,

11) the up hill scenario where stuck half way, when in 4LO, ALL 4 Jeep wheels are powered, unless one or two are slipping....within a fraction of a second, the other one will lock on and increase traction to keep climbing,

12) it won't be making a wheel spin divot losing momentum much at all before the other side locks on and lets you move up......
These statements contain much incorrect understanding of how TruTracs (and LSD in general) works.

LSDs do not "lock up" after a tire "starts slipping". Once a tires starts slipping (spinning faster than the other tire on the same axle), this means that you have exceeded the LSD's capabilities to keep the diff "locked", and the only thing that can cause the LSD to "lock up" again is to either encounter more traction on the spinning side, or reduce throttle to reduce the total torque demand at the axle.

Some explanation of how different types of differentials work: Your differential and µ - How traction works.

The TrueTrac has about a 3:1 torque bias, meaning that it withstand up to a 3:1 torque split across the axle before the differential itself will "slip", allowing the two tires to rotate at different speed (this is what the "limited slip" refers to; not slipping of the tires).

Examples...

To keep things simple, imagine driving straight in 2WD up a hill at a steady speed. Cruising along steadily, let's say it requires 40 ft-lbs torque at the axle to maintain speed. We will also ignore BLD for these examples.

Both rear tires have equal traction right now, so that torque is split evenly between both sides (20 ft-lbs per tire). You encounter a patch of snow on the right side that can only support 15 ft-lbs torque from your tire before losing traction. Once the tire starts slipping, the tire can only transmit 10 ft-lbs torque to the snow-covered road (kinetic coefficient of friction is less than the static coefficient) (btw - I made these numbers up for the sake of example; doesn't matter whether the exact numbers are correct, the concepts still apply)..

If you have an open diff in the rear, your right tire will start spinning when it hits the snow, and will only be able to apply 10 ft-lbs to the snow. Since open diffs always split torque 50:50, your left tire will also only be able to apply 10 ft-lbs to the road. So you end up with only a total of 20 ft-lbs torque applied to the road and snow (not enough to maintain speed), and a spinning right tire. The only way to stop the right tire from spinning is to reduce throttle so that that there is less than 20 ft-lbs total is applied to the rear axle and wait for the right tire to slow down and match the speed of the left tire (stop slipping). Once the right tire regains traction, you could increase throttle up to a total of 30 ft-lbs at the axle (still not enough to maintain speed) before the right tire starts slipping again.

If you have TrueTrac in the rear, it will maintain full traction and keep the axle "locked" as long as the torque demand across the axle is split no more than 3:1. With our total torque at the axle being 40 ft-lbs, that comes out to a 30:10 split at most. The right tire on the snow can exert up to 15 ft-lbs without slipping, so the TrueTrac will stay "locked" in this example. You'll continue driving up the hill without any tires slipping. The TrueTrac does its job without any drama, and the driver isn't even aware that anything special happened.

Now lets say you try to accelerate a bit as you hit this patch of snow. You press the throttle and try to apply 80 ft-lbs torque. The most split the diff could handle is 60:20 (3:1 split of the total of 80). 20 is more than the 15 that the snow can handle, so the right tire starts spinning. Now the spinning right tire can only exert 10 ft-lbs against the snow. The TrueTrac still maintains its 3:1 torque bias, so the left tire gets 3 times the right tire's torque = 30 ft-lbs for a total of 40 ft-lbs at the axle. No matter how much throttle you give it at this point, as long as the tire is still spinning, no matter how fast it spins, you still put a total of 40 ft-lbs to the ground, which for the definition of this example, is exactly enough to maintain speed, but not accelerate.

So then you let off the throttle until the tire stops spinning and more gently re-apply the throttle this time. The right tire on the snow can support up to 15 ft-lbs torque on the snow before slipping. Multiply that by 4 to get the total torque at the axle that the TrueTrac can handle before its torque bias is exceeded: 60 ft-lbs. So you can press the throttle up to the point of 60 ft-lbs torque at the axle before the right tire starts spinning, which is more than the 40 requires to maintain steady speed, so you will accelerate.
 

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Discussion Starter · #15 ·
These statements contain much incorrect understanding of how TruTracs (and LSD in general) works.

LSDs do not "lock up" after a tire "starts slipping". Once a tires starts slipping (spinning faster than the other tire on the same axle), this means that you have exceeded the LSD's capabilities to keep the diff "locked", and the only thing that can cause the LSD to "lock up" again is to either encounter more traction on the spinning side, or reduce throttle to reduce the total torque demand at the axle.

Some explanation of how different types of differentials work: Your differential and µ - How traction works.

The TrueTrac has about a 3:1 torque bias, meaning that it withstand up to a 3:1 torque split across the axle before the differential itself will "slip", allowing the two tires to rotate at different speed (this is what the "limited slip" refers to; not slipping of the tires).

Examples...

To keep things simple, imagine driving straight in 2WD up a hill at a steady speed. Cruising along steadily, let's say it requires 40 ft-lbs torque at the axle to maintain speed. We will also ignore BLD for these examples.

Both rear tires have equal traction right now, so that torque is split evenly between both sides (20 ft-lbs per tire). You encounter a patch of snow on the right side that can only support 15 ft-lbs torque from your tire before losing traction. Once the tire starts slipping, the tire can only transmit 10 ft-lbs torque to the snow-covered road (kinetic coefficient of friction is less than the static coefficient) (btw - I made these numbers up for the sake of example; doesn't matter whether the exact numbers are correct, the concepts still apply)..

If you have an open diff in the rear, your right tire will start spinning when it hits the snow, and will only be able to apply 10 ft-lbs to the snow. Since open diffs always split torque 50:50, your left tire will also only be able to apply 10 ft-lbs to the road. So you end up with only a total of 20 ft-lbs torque applied to the road and snow (not enough to maintain speed), and a spinning right tire. The only way to stop the right tire from spinning is to reduce throttle so that that there is less than 20 ft-lbs total is applied to the rear axle and wait for the right tire to slow down and match the speed of the left tire (stop slipping). Once the right tire regains traction, you could increase throttle up to a total of 30 ft-lbs at the axle (still not enough to maintain speed) before the right tire starts slipping again.

If you have TrueTrac in the rear, it will maintain full traction and keep the axle "locked" as long as the torque demand across the axle is split no more than 3:1. With our total torque at the axle being 40 ft-lbs, that comes out to a 30:10 split at most. The right tire on the snow can exert up to 15 ft-lbs without slipping, so the TrueTrac will stay "locked" in this example. You'll continue driving up the hill without any tires slipping. The TrueTrac does its job without any drama, and the driver isn't even aware that anything special happened.

Now lets say you try to accelerate a bit as you hit this patch of snow. You press the throttle and try to apply 80 ft-lbs torque. The most split the diff could handle is 60:20 (3:1 split of the total of 80). 20 is more than the 15 that the snow can handle, so the right tire starts spinning. Now the spinning right tire can only exert 10 ft-lbs against the snow. The TrueTrac still maintains its 3:1 torque bias, so the left tire gets 3 times the right tire's torque = 30 ft-lbs for a total of 40 ft-lbs at the axle. No matter how much throttle you give it at this point, as long as the tire is still spinning, no matter how fast it spins, you still put a total of 40 ft-lbs to the ground, which for the definition of this example, is exactly enough to maintain speed, but not accelerate.

So then you let off the throttle until the tire stops spinning and more gently re-apply the throttle this time. The right tire on the snow can support up to 15 ft-lbs torque on the snow before slipping. Multiply that by 4 to get the total torque at the axle that the TrueTrac can handle before its torque bias is exceeded: 60 ft-lbs. So you can press the throttle up to the point of 60 ft-lbs torque at the axle before the right tire starts spinning, which is more than the 40 requires to maintain steady speed, so you will accelerate.

Well, thanks for a very technical explanation. You must be a mechanic or an engineer!! I helps understand further some more details.

I do not think I misunderstood the concept at all. Although, I never felt the need to get into this much technical research.

The goal was to just learn how it behaves and be able to articulate it in layman terms so I can relate to the practical scenario based analysis of its benefits.

Bottom line: the wheel with lower traction, i.e. the one spinning on loose or slippery surface normally gets ALL the power in a Jeep. WITH Tru Trac, the other stationary wheel gets power distribution to move with it to get you out. It engages the stationary wheel quick enough to be effective, no clutch to wear quick, uses helical hears, etc. Perfect balance between nothing and lockers, considering cost/benefit.

Thank you for taking the time to explain the technicalities though.
 

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Yeah, I'm a software engineer with general curiosity in math, physics, and how things work. And I have a brother that has multiple college degrees in math and physics that is also quite interested in understanding how vehicles work. And a father in law that is an engineer at GM. I get involved in some incredibly geeky research, discussions, and analysis of how stuff works. It's great family bonding.


With the LSD, I think the biggest thing to understand that many people seem to ignore in descriptions of what they do, is that the LSD helps prevent a tire from slipping in the first place. It doesn't require a tire to start slipping before it will "engage".

And particularly important to the TrueTrac design is that the effect of the LSD is proportional to the amount of torque applied to the axle. So a TrueTrac in the front will behave just like an open diff when in 2WD, and even TrueTrac in the rear will act just like an open diff when coasting through a corner, and very near like open diff when maintaining speed or only gently accelerating through a corner. So they won't interfere with how the Jeep corners when driving "normal"/gently.
 

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Be sure to report back with your thoughts on how TrueTrac front and rear. That's exactly what I want to do with my Jeep when I can come up with the money for a regear and 2 TrueTracs. After I come up with money for tires and wheels...
 

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Question to the OP. I am in the same position as you (3.21 need to re-gear to 4.56).

My question is have you already considered the Auburn Ected Max which is both an LSD and an electric locker? Perhaps you have decided already decided against it. Just curious what your selection process was to narrow down your options to the TruTrac and and the Eaton e-locker.
From what I have heard, Auburn lockers are garbage. They fail all the time. Even if you get one that doesn't fail, it's still a clutch based system, so the clutch will eventually wear out anyway.
 

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Discussion Starter · #19 ·
With the LSD, I think the biggest thing to understand that many people seem to ignore in descriptions of what they do, is that the LSD helps prevent a tire from slipping in the first place. It doesn't require a tire to start slipping before it will "engage".

And particularly important to the TrueTrac design is that the effect of the LSD is proportional to the amount of torque applied to the axle. So a TrueTrac in the front will behave just like an open diff when in 2WD, and even TrueTrac in the rear will act just like an open diff when coasting through a corner, and very near like open diff when maintaining speed or only gently accelerating through a corner. So they won't interfere with how the Jeep corners when driving "normal"/gently.[/QUOTE]

Well, your knowledge of the mechanics was obvious!!

Learning the first segment above actually makes it even a better device than I thought.

I did learn and understand the second portion about it being open until it kicks in.

Thanks
 
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Discussion Starter · #20 ·
Be sure to report back with your thoughts on how TrueTrac front and rear. That's exactly what I want to do with my Jeep when I can come up with the money for a regear and 2 TrueTracs. After I come up with money for tires and wheels...
Sure, will do. Installation is set for March 8th. Will report back after that.
 
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