Front Lockers

[Tncdrew]

Sorry, it spell checked it. FAD

Yes, mine has FAD, although that has nothing to do with the Torq Locker turning the driveshaft.

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[apensity]

Yes, mine has FAD, although that has nothing to do with the Torq Locker turning the driveshaft.

If you didn't remove the FAD, that would cause the vibration.

 

[Zandcwhite]

If you didn't remove the FAD, that would cause the vibration.

The vibration is caused by the pinion angle and the driveshaft turning. If you remove the fad the driveshaft will always be turning with no front locker, an arb, or a torque locker. That's why the '24 and up models are having more vibration issues after a lift than the earlier models. By keeping the FAD and going to an ARB the front shaft only sounds in 4wd. The torq locker, or any auto locker or limited slip will transfer the spinning force of the drivers side tire to both the passenger side shaft that is disconnected and the ring gear and cause the driveshaft to spin even in 2wd effectively making the FAD useless but it's not the FAD causing the vibration it is the front driveshaft.

 

[Tncdrew]

If you didn't remove the FAD, that would cause the vibration.

That is incorrect, and here's why...
With FAD engaged (travelling straight), both side gears in a manual locker (as in the Torq Locker), are always engaged, therefore always turning the driveshaft. When in a turn, the outside driven side gear will disengage to allow "overrun", but there will always be one side gear turning the driveshaft. This is the same operation as if you had a FAD delete, or no FAD at all.
This is the operation of all "lunchbox" lockers, Torq Locker, Aussie, Spartan, etc. as well as the classic Detroit No-Spin locker - the ability to disengage the outside wheel in a turn.
These types of lockers will ALWAYS spin your driveshaft.
Open differentials, by design, will not spin your driveshaft. The design of an ARB air locker when unlocked acts as an open differential. When engaged, the ARB acts like a spool, and does not allow for "overrun" in a turn.

 

[apensity]

That is incorrect, and here's why...
With FAD engaged (travelling straight), both side gears in a manual locker (as in the Torq Locker), are always engaged, therefore always turning the driveshaft. When in a turn, the outside driven side gear will disengage to allow "overrun", but there will always be one side gear turning the driveshaft. This is the same operation as if you had a FAD delete, or no FAD at all.
This is the operation of all "lunchbox" lockers, Torq Locker, Aussie, Spartan, etc. as well as the classic Detroit No-Spin locker - the ability to disengage the outside wheel in a turn.
These types of lockers will ALWAYS spin your driveshaft.
Open differentials, by design, will not spin your driveshaft. The design of an ARB air locker when unlocked acts as an open differential. When engaged, the ARB acts like a spool, and does not allow for "overrun" in a turn.

Yeah, I think we’re both actually right here — just looking at it from slightly different angles.
FAD-equipped Jeeps with a front lunchbox locker are definitely more prone to vibration in 2WD because the locker forces torque across the carrier, spinning the driveshaft via one axle shaft while the other is disconnected. That torque imbalance is what introduces the shake — not the FAD itself, but the way the locker interacts with it.
Now, where I pushed back was on the idea that even open diffs would cause vibration. I’ve got a 2024 with no FAD, 3.5" lift, open diffs — front shaft spins all the time, but no vibration at all. So, open diffs alone don’t seem to be the issue.
That said, if I did install a lunchbox up front, I fully expect I’d start getting some vibration too, just due to the driveshaft now being driven under load 100% of the time. So yeah, we’re both seeing the same physics, just in slightly different configurations. Am I wrong here?

 

[Zandcwhite]

Yeah, I think we’re both actually right here — just looking at it from slightly different angles.
FAD-equipped Jeeps with a front lunchbox locker are definitely more prone to vibration in 2WD because the locker forces torque across the carrier, spinning the driveshaft via one axle shaft while the other is disconnected. That torque imbalance is what introduces the shake — not the FAD itself, but the way the locker interacts with it.
Now, where I pushed back was on the idea that even open diffs would cause vibration. I’ve got a 2024 with no FAD, 3.5" lift, open diffs — front shaft spins all the time, but no vibration at all. So, open diffs alone don’t seem to be the issue.
That said, if I did install a lunchbox up front, I fully expect I’d start getting some vibration too, just due to the driveshaft now being driven under load 100% of the time. So yeah, we’re both seeing the same physics, just in slightly different configurations. Am I wrong here?

ITS THE FRONT DRIVESHAFT PERIOD. Imbalance, the stub shaft from fad to the center is now spinning despite the FAD being disengaged where it was before because the drivers side tire was spinning the spiders. The difference is without the locker the carrier stayed stationary but both front shafts still spin. And unless your passenger tire is off the ground, that stub shaft is spinning just like the drivers side. The fad allows carrier and front driveshaft to not spin and nothing more. And the locker isn't creating a torque imbalance as in 2wd there's no torque applied. You likely run caster on the lower side which keeps the pinion angle more optimal which is why you don't have vibrations. Is your front shaft stock, as the rzeppa joint is more angle tolerant without vibes than an aftermarket double cardan/ujoint shaft? If you want to run 6⁰ or more of caster with 2.5" or more of lift you will get vibes. The more caster the worse it will be unless you cut and turn the knuckles for a better pinion angle.

 

[Tncdrew]

Yeah, I think we’re both actually right here — just looking at it from slightly different angles.
FAD-equipped Jeeps with a front lunchbox locker are definitely more prone to vibration in 2WD because the locker forces torque across the carrier, spinning the driveshaft via one axle shaft while the other is disconnected. That torque imbalance is what introduces the shake — not the FAD itself, but the way the locker interacts with it.
Now, where I pushed back was on the idea that even open diffs would cause vibration. I’ve got a 2024 with no FAD, 3.5" lift, open diffs — front shaft spins all the time, but no vibration at all. So, open diffs alone don’t seem to be the issue.
That said, if I did install a lunchbox up front, I fully expect I’d start getting some vibration too, just due to the driveshaft now being driven under load 100% of the time. So yeah, we’re both seeing the same physics, just in slightly different configurations. Am I wrong here?

I wasn't accurate when I said, "Open diffs by design, will not spin your driveshaft". They will in the case of no FAD (or standard live axle config.).
My '22 with a FAD however, does not spin the driveshaft when the FAD is disengaged (2WD).
I remember testing this after I installed the ARB, and just tested it again by jacking up slightly the driver side only, spinning the tire, and observing no driveshaft rotation.

Which brings me back to my reasons for swapping out the TL for ARB...
I did experience slight vibs at speed with the TL, and just don't like the idea of my front driveshaft spinning 100% of the time.

 

[Tncdrew]

@apensity I MUCH prefer the manual locking front hubs of the CJ's to that of Wranglers

 

[apensity]

@apensity I MUCH prefer the manual locking front hubs of the CJ's to that of Wranglers

Yeah, I had a 77 CJ-5 with 304 and 3 speed and loved it. It was always doing something crazy, but it was a beast, uncomfortable, and felt like a true offroader.

 

[AdamG]

To go along with Tncdrew, not everyone will have vibration. I have a TrueTrac in front, 3” lift (actual), and eliminated my FAD, and don’t have any vibration. I think there’s enough tolerance in the system and components that some get it and some don’t.

 

[apensity]

To go along with Tncdrew, not everyone will have vibration. I have a TrueTrac in front, 3” lift (actual), and eliminated my FAD, and don’t have any vibration. I think there’s enough tolerance in the system and components that some get it and some don’t.

How do you like the TT on-road? Any significant issues? Thanks for the previous info.

 

[AdamG]

I have them both front and rear, when I regeared I replaced the rear OEM and did a front as well. I’m not awesome at offroading so didn’t want a locker, I just wanted to drive and the Jeep would do what it would do, and I had no locker experience. Ran with the FAD for a while, then decided to eliminate it with the 392 (I guess now the same as as 2025 Rubicon) plate and collar to tie the shafts together. A lot easier and cheaper than replacing with a 1-pc shaft, plate went on in minutes. So the rear TT is awesome, invisible in normal driving but hooks up immediately when it slips. The two of them together offroad or in the snow are great, the Jeep just claws and grabs at any bit of traction.

TLDR, I love them, no regrets.

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