2LO - installed

[Figmo]

PSA: Be careful. Remember you sending everything the transmission puts out to the rear axle only now. Which effectively doubles the torque and stress on that axle when in a bind. 2LO can absolutely get you out of a few jams. But forgetting the physics can also net you a broken axle. Use with caution.

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[Zachanadandy]

PSA: Be careful. Remember you sending everything the transmission puts out to the rear axle only now. Which effectively doubles the torque and stress on that axle when in a bind. 2LO can absolutely get you out of a few jams. But forgetting the physics can also net you a broken axle. Use with caution.

V6 torque output in 2Lo is still unimpressive, especially in reverse. 260ftlbs x 3.3 x 2.73 x 4.10 (assuming non-rubicon but giving the advantage of max tow/mojave axle gears) is only 9,604ftlbs. Conversely the 392 JLUR gets the same rear axle and has 470ftlbs of torque. In 1st gear that's 470x4.7x2.73x4.56 or 27,500 ftlbs. Split between 2 axles that's still 13,750ftlbs per axle...and that ignores the torque multiplication of the torque converter vs the manual JT. And I'm guessing those 392 guys are much more likely to send it than a JT guy so concerned about the garbage clutch that he's using 2LO to back up his trailer. Long winded explanation as to why I wouldn't worry about it fit a second... because physics.

 

[JeepOfTheseus]

When the FAD is disconnected, there is no drive to the front wheels. That is totally out of the picture. REAR only…..(no FAD on the rear)

FAD is physically on the passenger half shaft. It being “disconnected” only severs that shaft in half.

I assume “2LO” still sends power to the front driveshaft since the transfer case is engaged, no?

 

[Dilly’S Willy]

I guess you can call it 2L with the FAD, but really its just 3L on an open differential since 3 wheels still get potential power even with the FAD forced open/unlocked. Only now you don't have remotely as much axle bind since you're now only fighting ONE turned wheel rotating at a different speed than the rear axle, and the open diffs eat up that extra loss of power though the FAD.

@ryanlsmith Yes, the driver front axle is still being sent power, just losing most of it when the front has grip through the FAD/diff spiders. This is due to the t-case being locked 50/50 mechanically. So as @Figmo stated: BE CAREFUL!

 

[rharr]

I guess you can call it 2L with the FAD, but really its just 3L on an open differential since 3 wheels still get potential power even with the FAD forced open/unlocked. Only now you don't have remotely as much axle bind since you're now only fighting ONE turned wheel rotating at a different speed than the rear axle, and the open diffs eat up that extra loss of power though the FAD.

@ryanlsmith Yes, the driver front axle is still being sent power, just losing most of it when the front has grip through the FAD/diff spiders. This is due to the t-case being locked 50/50 mechanically. So as @Figmo stated: BE CAREFUL!

You are slightly right and slightly wrong.

You get no power to the front wheels, when FAD is disabled. The front drive shaft does turn and the power is then sent to the spider gears in the open dif. If the driver wheel finds traction then that spider gear stops turning and the diff starts spinning the other spider gear to try and transfer power to the passenger side wheel but can't because the stub shaft just spins with the FAD disabled. All the power goes to spinning the spider gears and diff, nothing is transferred to the wheels unless you count the tiny bit of power you get from friction drag of the spider gears.

IF I locked the front dif with the FAD disabled then i would get 3WD.

I am not that worried about overloading the rear axle i think that is ppl overthinking thinks on the internet. what about when you are in 4lo and have a front tire in the air or low traction and that one rear wheel is hooked on good traction (rear locked) and pulling the rig over a obstacle? Is that not any different then 2lo and ppl aren't worrying about that?

Here in AZ were i wheel we have lots of hi traction surfaces with lots of big rocks and varying terrain, I generally need low gear to help traverses stuff in a controlled manner, not because I need the traction. Like stated above, 2lo helps you steer better when you have a tight turn.

You can do a lot in 2lo rear locked.

I have a automatic trans and diesel, so i guess i am royally screwed if you ask the internet.

 

[Janster]

FAD is physically on the passenger half shaft. It being “disconnected” only severs that shaft in half.

I assume “2LO” still sends power to the front driveshaft since the transfer case is engaged, no?

<scratching head to try and explain it>
It’s the magic within the diff(open) that makes it all work.

This is a nice video to explain it …


I’m not familiar with the 2lo mod…. It’s not a modification you see very often.
I would assume the t-case would send power to the front driveshaft while in 4lo but because the FAD is disconnected (modified accordingly), there wouldn’t be any power to the wheels. Again, the magic happens inside the OPEN diff.

 

[Zachanadandy]

<scratching head to try and explain it>
It’s the magic within the diff(open) that makes it all work.

This is a nice video to explain it …


I’m not familiar with the 2lo mod…. It’s not a modification you see very often.
I would assume the t-case would send power to the front driveshaft while in 4lo but because the FAD is disconnected (modified accordingly), there wouldn’t be any power to the wheels. Again, the magic happens inside the OPEN diff.

The question I have is that if it's tricking the Jeep into thinking it's in 4lo and the FAD is working, wouldn't the BLD engage and start applying the brakes up front in order to get the front wheels to pull?

 

[Badunit]

The question I have is that if it's tricking the Jeep into thinking it's in 4lo and the FAD is working, wouldn't the BLD engage and start applying the brakes up front in order to get the front wheels to pull?

I would think since the front wheel are not slipping/spinning, the computer would think they have full traction so no brakes would be applied to the front wheels.

 

[Zachanadandy]

I would think since the front wheel are not slipping/spinning, the computer would think they have full traction so no brakes would be applied to the front wheels.

The wheel speed sensors would be looking to match all 4 tires I think. In my mind it would see the front as maybe not slipping when the rear is and brake the rear but I'm not 100% sure how the algorithm works. I've never found a need for 2lo so it won't effect me either way but it seems like it could freak the traction control system out?

 

[Figmo]

Do you know if the relays are NO or NC? I ask because relays fail sometimes. In a failure situation, will FAD be bypassed or engaged?

If disconnected is the default failure mode - then mounting those relays in a more accessible spot would be a wise precaution to keep from being stranded somewhere that you needed the front axle to get in to - and now can't get out of.

Heck, it might be wise regardless. Just to make servicing them less of a nightmare.

Food for thought for others going this route (which I confess.....I am considering)

 

[rharr]

Do you know if the relays are NO or NC? I ask because relays fail sometimes. In a failure situation, will FAD be bypassed or engaged?

If disconnected is the default failure mode - then mounting those relays in a more accessible spot would be a wise precaution to keep from being stranded somewhere that you needed the front axle to get in to - and now can't get out of.

Heck, it might be wise regardless. Just to make servicing them less of a nightmare.

Food for thought for others going this route (which I confess.....I am considering)

You make a good point about the relays, never did look at them that closely, they looked like a typical 5 pin relay. If I do run into a relay issue I should be able to pull the Fad cover off and manually lock the axle I would think. Or I just lock the diff and work with 3wd.

 

[Supazuk]

What would be the point in having 2lo? When would you need to use it?

moving a trailer

 

[Bandit’s Lair]

Here in AZ were i wheel we have lots of hi traction surfaces with lots of big rocks and varying terrain, I generally need low gear to help traverses stuff in a controlled manner, not because I need the traction. Like stated above, 2lo helps you steer better when you have a tight turn.

You can do a lot in 2lo rear locked.

This. Some of those ridge runs in AZ have some pretty tight turns with massive drop offs on the other side. Even when not locked but in 4WD it’s pretty sketchy making the turn at the top. When that outer front tire starts tickling the downside you can start losing seat cushions in uncomfortable places.

 

[Jeep Stuff]

The wheel speed sensors would be looking to match all 4 tires I think. In my mind it would see the front as maybe not slipping when the rear is and brake the rear but I'm not 100% sure how the algorithm works. I've never found a need for 2lo so it won't effect me either way but it seems like it could freak the traction control system out?

On a simple note ABS/Traction Control use the wheel speed sensors to monitor wheel rotation movement and will kick in to correct any speed discrepancy whenever it senses a tire or tires rotating at a faster or lower rate than the others like when a tire or tires slip or locks regardless of the drive mode so if the rear tires slip or lock while in 2lo then ABS/Traction Control will do it's work as in any tire slip or lock condition in any drive mode (2hi, 4hi, 4lo and in this case 2lo) so no problems there.

 

[rharr]

I for one don't want traction control on when I am wheeling, it's the first thing I turn off.

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