FAD Missing

[Zachanadandy]

THanks!! Interesting.... So, obviously the shaft is splined and runs thru that - and acts as a 'support'?? I can imagine those forks wearing away rather quickly.

The splines lock the inner and outer shafts together. If you look closely there are Teflon pads between the fork and splined coupler. The transfer case shift forks are similar. I'm guessing hundreds of thousands of miles before the Teflon wears down to metal on metal. The non-fad models just have a fixed fork vs the motor actuated fork that slides the collar off 1 shaft.

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[AustyPosty]

Adding caster decreases pinion angle, so I wouldn't say high caster results in a severe pinion angle with our axles. It actually results in low pinion angle.
As to the 2nd part of the statement, it's the opposite. The double cardan shaft needs the pinion pointed at the transfer case output to run smooth at high rpms/speed. This cannot be accomplished in a lifted Jeep if you want even decent caster. The rzeppa joints in the stock shaft are much more forgiving on the angles, but don't have the range of travel if you run long shocks with your lift. Without a FAD you're better off with the stock shaft and limiting droop to save the joints. The low separation angle between the pinion and the knuckles is the real problem.

Good info, thanks.

 

[heretic]

I was wondering on my 24 what method jeep used this one (two shafts and a fixed collar) or a solid axle?? You have an option depending on how you use your jeep. Installl a stock FAD actuator motor then run it manually with a switch from you aux panel for flexibility.

 

[Zachanadandy]

I was wondering on my 24 what method jeep used this one (two shafts and a fixed collar) or a solid axle?? You have an option depending on how you use your jeep. Installl a stock FAD actuator motor then run it manually with a switch from you aux panel for flexibility.

All JLs/JTs come with the 2 piece shafts and collar. Those with no FAD really have all the parts aside from the motor so adding it is an option.

 

[heretic]

Additional If you wanted true 4A you would need to throw the switch to lock the FAD. I'm guessing the factory speed limit rating would apply here, you are doing the same thing the factory does but manually RIGHT?

 

[Zachanadandy]

Additional If you wanted true 4A you would need to throw the switch to lock the FAD. I'm guessing the factory speed limit rating would apply here, you are doing the same thing the factory does but manually RIGHT?

Yes, shouldn't be speed limited at all. I wouldn't flip the switch under full throttle acceleration, but otherwise no issues doing it at even freeway speed just like 2H to 4H.

 

[heretic]

So honest question...is there any real value in adding a "manual FAD on/off switch"
some one brought up the pinion angle and reduced vibration reason also.

 

[Zachanadandy]

So honest question...is there any real value in adding a "manual FAD on/off switch"
some one brought up the pinion angle and reduced vibration reason also.

The pinion angle and potential drive shaft vibration are the only reasons in reality. Sure having the front shaft disconnected could theoretically slightly improve fuel economy, but I'd bet it's negligible which is why Stellantis started putting the fixed fork even on some JL models without 4A. If you're at stock height or low enough lift that you have good caster and drivability without vibrations then there's nothing to be gained.

 

[heretic]

Zac...TY,
MC game changer 3.5" now, caster angle is unknown shop did not say.
Honestly drives fine and no noise up front.
Seems like a kool see what I can do thing plus a little future proof mod.

 

[Stan H]

I have a 2024 Mojave X…..
Just crawled underneath to take a photo… If that’s not a FAD, then what’s in the box?

That is a block off plate which holds the connecting ring into the LOCK position . It will require removal and install of a actual FAD from a used axle . These FAD motors are very resilient and ordering a used one from say LKQonline.com and it will work the wiring is not present in tje harness but it is a simple matter of a switch and power . On and off.

 

[Stan H]

4A was available before the X models came out as an option pre 2023. Those models had a functioning FAD that engaged in 4A as well as 4H and 4L but was open in 2H.

@WILDHOBO has one .

 

[WILDHOBO]

@WILDHOBO has one .

I have to say, it’s one thing that makes me hesitant about an axle upgrade. I’m not crazy about my front driveshaft rotating when it’s in 2wd.

 

[Stan H]

I have to say, it’s one thing that makes me hesitant about an axle upgrade. I’m not crazy about my front driveshaft rotating when it’s in 2wd.

I dont think I will ever go to an axle without the FAD . The move you did with RCV's is the ticket .

 

[WILDHOBO]

I dont think I will ever go to an axle without the FAD . The move you did with RCV's is the ticket .

My concern is what do I do if I ever upgrade to aftermarket axles so I can get high pinion?

 

[CrazyCooter]

I sent 4x4 Posi-Lok a message last month on behalf of you poor saps who got screwed out if the FAD advising them of another application for their product, but never got a response as expected.

I've done a bunch of these over the years in Chevys and 2nd Gen Rams and think its the answer for this problem.

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