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Anti-Spin Differential Rear Axle Options?

6.2Blazer

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To address a couple posts above.

I'm not sure how 4 low could possibly make BLD (brake based traction control) work better versus 4 high. The comments about increased torque don't apply since you are looking at the torque difference between the left and right side tires, and that percent difference is the same. I would suspect any difference in operation would be because the BLD has a different algorithm it uses when the vehicle is in 4 low that is basically more aggressive (applies heavier brake application to the tire with less traction). The vehicle will be travelling slower when in 4 low and you make the assumption in off-road only conditions which requires more "traction" and less possibility of the negative handling it could cause. Again, I really don't understand how mechanically being in 4 low somehow makes BLD work better without the actual programming/electronic part of the system being different.

In regards to the Rubicon rear differential, at least back in the TJ years the rear diff was a LSD that could be completely locked up by activating the switch. Been out of the Jeep game since recently but seems like the current Rubicon rears are open diffs until locked and rely on the BLD (brake traction control) otherwise. I have a Power Wagon with locking diffs but the rear is an LSD under normal circumstances.

The combination of BLD and factory LSD is pretty effective off-road. Not the same as a locker (though I think if you programmed the BLD for off-road it would be better). I've been off-roading for 30 years and have ran a rig with Dana 60s, lockers front and rear, and 40" tires for 15 years and during that time have seen lots of stock-ish rigs on the trails. Have to admit to being fairly impressed with the JK's and JL's with just open diffs and BLD. Again, they don't work better than a locker but are much more capable with the BLD.
 

five9dak

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It is always working. It is a mechanical device. It will transfer up to about 3 times the available torque to the tire with the most traction with negligible delay if any. It doesn't "kick in" like BLD. It is so smooth it is almost impossible to notice when it is working. If the torque bias between both tires is higher than 1:3, meaning the tire with traction needs 3 times more than available torque to move the vehicle forward, it wont work at all. It is a torque multiplier, the tire with less traction needs a little traction to work, then whatever that traction is gets multiplied by 3.

" Please note that the wheel with grip receives 4 times the grip the other wheel can transfer to the road. It does not mean 100% of the engine torque can be used. Let’s say the engine puts out 300 Nm of torque and the spinning wheel can only transfer 50 Nm of torque to the surface it is on. In a regular open differential, the other wheel would receive 50 Nm of torque as well. The total amount of torque to the wheels is 100 Nm. In a Torsen differential with a 4:1 bias ratio, the other wheel will receive 200 Nm or torque. The total amount of torque to the wheels is now 250 Nm. "

https://www.kmpdrivetrain.com/differentials/torsen-vs-plated-limited-slip-differential/

Tires slipping doesn't mean your LSD isn't or is working. A lot of people confuse BLD with their limited slip, thinking that when BLD kicks that's the limited slip. it isn't
I was under the impression the stock LSD was a clutch type unit, not a torsion. I am only familiar with torsen differentials having a bias ratio. Usually clutch type units simply have a breakaway torque before which they will be locked, and above which, they will differentiate.

Do you have any Jeep material to show that the JL differential having a bias or ratio? Perhaps this design/layout I am not familiar with. Older dana and Chrysler units had their clutch packs between the spiders, I've seen some modern layouts with the clutch between the housing and one outside gear. I can imagine the spider gear separating force could increase clutch apply force, and therefor the breakaway torque.

I have some familiarity with older style units because the trac lock in my chysler 9.25 wore out and I replaced it with an eaton true trac (torsen). The difference in their performance is dramatic.

To the OP- I searched out a used JL with the d44 LSD, and it arrived worn out at 19k miles. By 30k miles it was broken. It is being replaced under powertrain warranty. It's failure has damaged my axle shafts, and the slop it has developed knocks on take off. The best course of action if you are really particular, is to check the option to get the D44 housing, and plan on replacing the differential carrier with a better aftermarket one near the end of your powertrain warranty. The LSD unit itself is very unreliable, there is like a 100 page thread about it.
 

entropy

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I was under the impression the stock LSD was a clutch type unit, not a torsion. I am only familiar with torsen differentials having a bias ratio. Usually clutch type units simply have a breakaway torque before which they will be locked, and above which, they will differentiate.

Do you have any Jeep material to show that the JL differential having a bias or ratio? Perhaps this design/layout I am not familiar with. Older dana and Chrysler units had their clutch packs between the spiders, I've seen some modern layouts with the clutch between the housing and one outside gear. I can imagine the spider gear separating force could increase clutch apply force, and therefor the breakaway torque.

I have some familiarity with older style units because the trac lock in my chysler 9.25 wore out and I replaced it with an eaton true trac (torsen). The difference in their performance is dramatic.

To the OP- I searched out a used JL with the d44 LSD, and it arrived worn out at 19k miles. By 30k miles it was broken. It is being replaced under powertrain warranty. It's failure has damaged my axle shafts, and the slop it has developed knocks on take off. The best course of action if you are really particular, is to check the option to get the D44 housing, and plan on replacing the differential carrier with a better aftermarket one near the end of your powertrain warranty. The LSD unit itself is very unreliable, there is like a 100 page thread about it.
It is a torque-sensing unit. It is called Dana Trac-Lok. You can google it and there is plenty of information online about the unit. It is designed for medium-duty applications. According to Dana the torque bias-ratio is about 2.7:1. Since it is a torque sensing unit it doesn't work like the common clutch type LSDs where there is a pre-load. This one doesn't lock at all until it senses a torque bias. So it is always open. This is a good thing for a clutch based type LSD; theoretically this would allow the limited slip differential to work for a very long time if working properly. But there are plenty of reports of people saying they failed prematurely and also people who ran them for over 100k miles. So who freaking knows.

The design did change from JK to JL. But it is hard to find actual specs online. With these units you can't do the standard test you could on JKs were you would jack the rear and spin tires. This one behaves like an open diff when you do that because of the non-existent pre-load.

I used to think these were not designed to handle large tires, thus the failures. But Jeep put it in the willys xtreme which comes with 35s. So....

I test almost every time I go on the trail by doing a burnout on dirt. It is still going strong for me. But at 20k miles only it better be lol. It works alright until you lift a rear tire or when you start dragging the belly on a rock. I kinda want it to not work to have an excuse to install a rear locker lol.

I've crawled through obstacles were people twin lock their Rubis to be able to go through. I am front locked. The only times I've gotten stuck I am stuck somewhere on the belly and a rear tire is either on the air or has very little contact with dirt. A rear locker might be able to pull me out on these situations or an extra inch of clearance (spacer) might do the trick. Either way, a quick single line winch pull gets me out so I can still have fun. I will be regearing sometime next year so locker is going in anyway.

The EATON true trac is probably the best LSD available in the market. But if going through the trouble of installing one I'd do a locker instead. I personally don't think limited slips belong in wranglers. But that's just my biased opinion.
 
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five9dak

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The EATON true trac is probably the best LSD available in the market. But if going through the trouble of installing one I'd do a locker instead. I personally don't think limited slips belong in wranglers. But that's just my biased opinion.
Thanks. I put the true trac in my street/strip truck. It works great for that.

Medium duty trak lok shows a torsen.
https://www.worktruckonline.com/10122747/danas-trac-loc-limited-slip-differential-new-for-medium-duty#:~:text=During a slip event, it,turns, and boosting driver productivity.

Parts images show a clutch type - see large spider gear?
https://www.quadratec.com/p/mopar/rear-dana-44-trac-lok-assembly-wrangler-jl-68474060AB

This thread with user photos of an D44 LSD clearly show it has large spider gears, not helical gearing like a torsen.

Methinks dana is marketing multiple devices under the same name, and possibly JL is light duty, not medium duty. I think you may have been confused / deceived. It appears the JL unit is still clutch friction type. I hope I am wrong, I would rather have the torsen type (they are installing the new on this week.)


EDIT: link didn't paste.
https://www.jlwranglerforums.com/forum/threads/knock-in-rear-with-dana-44.16921/page-11
 
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Thanks. I put the true trac in my street/strip truck. It works great for that.

Medium duty trak lok shows a torsen.
https://www.worktruckonline.com/10122747/danas-trac-loc-limited-slip-differential-new-for-medium-duty#:~:text=During a slip event, it,turns, and boosting driver productivity.

Parts images show a clutch type - see large spider gear?
https://www.quadratec.com/p/mopar/rear-dana-44-trac-lok-assembly-wrangler-jl-68474060AB

This thread with user photos of an D44 LSD clearly show it has large spider gears, not helical gearing like a torsen.

Methinks dana is marketing multiple devices under the same name, and possibly JL is light duty, not medium duty. I think you may have been confused / deceived. It appears the JL unit is still clutch friction type. I hope I am wrong, I would rather have the torsen type (they are installing the new on this week.)


EDIT: link didn't paste.
https://www.jlwranglerforums.com/forum/threads/knock-in-rear-with-dana-44.16921/page-11
people have replaced clutch packs so it’s definitely a clutch type.
 

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I took my Willys over Imogene and Ophir Pass a few weeks ago. I know I used my factory LSD and I'm glad I brought it with me. Twas helpful!
 

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Okay been watching the ping pong match between Tyler and entropy. My head is going back and forth. You guys need to have a beer or 3 together and continue the discussion properly. :LOL:

That said, and I'm new to the game, so maybe someone help me understand how 4WD Auto feature fits is related to this discussion? I am several months and a couple of BOH trails into this Jeep thing and optioned my Rubi with 4WD but I haven't researched how it actually works.

My apologies to the OP for potentially highjacking this thread but it is a learning experience, no?
 

stumblinhorse

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Okay been watching the ping pong match between Tyler and entropy. My head is going back and forth. You guys need to have a beer or 3 together and continue the discussion properly. :LOL:

That said, and I'm new to the game, so maybe someone help me understand how 4WD Auto feature fits is related to this discussion? I am several months and a couple of BOH trails into this Jeep thing and optioned my Rubi with 4WD but I haven't researched how it actually works.

My apologies to the OP for potentially highjacking this thread but it is a learning experience, no?
Since you have a rubicon. You don’t even need to be in this conversation. Rubi’s don’t have LSD. Just BLD and lockers. That is the number 2 reason I always bought a rubicon. I hate LSDs. They are unpredictable in icy conditions and will by design slide your vehicle sideways. Most people don’t experience that because they engage 4wd. But that is not how I drive. Open diff with BLD is much easier to control on icy conditions in my opinion and my experience.

And I don’t want to stir it up again, but there is a lot of confusion on how a LSD works in this thread. People tend to think that with an LSD everything works like magic. It doesn’t. That is why lockers exists. If you have an LSD without BLD and you get a wheel off the ground, the LSD will spin the wheel in the air and you are now stuck. if there is no friction/resistance the LSD cannot put power to the wheel on the ground, that is why it is good to have BLD. But in everyday driving tires stay on the ground and force can be spread to the tires. LSD works good for rain, mud and sand etc. But on ice and snow in 2wd an open diff will keep you straight with the 50/50 power and BLD aids because it ensures the wheels turn at the same speed…
 

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And I don’t want to stir it up again, but there is a lot of confusion on how a LSD works in this thread. People tend to think that with an LSD everything works like magic. It doesn’t. That is why lockers exists. If you have an LSD without BLD and you get a wheel off the ground, the LSD will spin the wheel in the air and you are now stuck. if there is no friction/resistance the LSD cannot put power to the wheel on the ground, that is why it is good to have BLD. But in everyday driving tires stay on the ground and force can be spread to the tires. LSD works good for rain, mud and sand etc. But on ice and snow in 2wd an open diff will keep you straight with the 50/50 power and BLD aids because it ensures the wheels turn at the same speed…
LSD + BLD work in tandem. LSD does nothing when a wheel is on the air as you stated. But when BLD kicks in the LSD will multiply the applied torque to the tire with traction if needed, enhancing the BLD capabilities.

There is this effect that occurs with a rear locker and open front when on difficult uphill obstacles where the front tends to lift off the ground due to the traction from the rear as the rear wants to push the jeep up no matter what. This doesnt happen with BLD. But I experienced it many many times with my LSD and it is one of the main reasons I got a front locker. When both rear tires are touching the ground that LSD will provide consistent traction BLD alone will never be able to. BLD provides short bursts of torque with a noticeable lag.


In my experience, driving on an icy road on 2wd with LSD is terrible too. The rear kicks to the sides unpredictably.
 
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LSD + BLD work in tandem. LSD does nothing when a wheel is on the air as you stated. But when BLD kicks in the LSD will multiply the applied torque to the tire with traction if needed, enhancing the BLD capabilities.

There is this effect that occurs with a rear locker and open front when on difficult uphill obstacles where the front tends to lift off the ground due to the traction from the rear as the rear wants to push the jeep up no matter what. This doesnt happen with BLD. But I experienced it many many times with my LSD and it is one of the main reasons I got a front locker. When both rear tires are touching the ground that LSD will provide consistent traction BLD alone will never be able to. BLD provides short bursts of torque with a noticeable lag.


In my experience, driving on an icy road on 2wd with LSD is terrible. The rear kicks to the sides unpredictably.
Agree BLD is good for open and LSD And they complement each other. BLD will make it so rock crawling without lockers with an LSD you can many times keep moving enough when a wheel lifts. If you can apply enough throttle. For an open diff in slippery conditions it helps keep you straight.
 

five9dak

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Does LSD help on cornering?
Technically you can apply more power earlier on corner exit without spinning your inside tire.

But if you are driving your jeep this way, you bought the wrong vehicle.
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