FAD Delete

[ShadowsPapa]

Theory and practice are sometimes different, which is why I asked him to report back. JL owners report vibrations. If it performs like past Jeeps, I would be fine with it. There are JL guys who have deleted FAD, then gone back because of their experience.

Do they have lifts and a driveshaft angle issue?

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[Harold0819]

Report back whether you experience any driveline vibrations after driving for a while without FAD. Some JL owners claim they do, from the driveshaft turning...

I will. Technically it should be fine but I'm prepared to throw an Adams front shaft in if needed. Wouldn't surprise me if Jeep doesn't have these all well balanced given they aren't spinning full time like the previous JKs

 

[Harold0819]

It creates a little more drag by causing the driveshaft to rotate while driving. Wranglers did this from 1990-2018, so it’s not new, but some JL owners report vibrations after the delete. I generally don’t like FAD (had to bypass mine on a YJ years ago on a trail), but haven’t had problems out of it in the JT (yet).

Agreed...had a Comanche back in the 80s. Couldn't stand the vacuum system, had it fail me and replaced it a cable system that was available at the time.

 

[Harold0819]

got it. so instead of just the wheels turning... the wheels and shafts turn, but the differential still isn't engaged... is that it?

The whole system is spinning, disengaged in the transfer case.

 

[Harold0819]

Theory and practice are sometimes different, which is why I asked him to report back. JL owners report vibrations. If it performs like past Jeeps, I would be fine with it. There are JL guys who have deleted FAD, then gone back because of their experience.

I'll keep you posted. It should be fine but will see. The stock front shaft will only last so long before the front boot tears from flexing. Then an aftermarket will replace it. To me, the only downfall is how quickly I'll have to go to an aftermarket shaft.

 

[mazeppa]

Also with the FAD, shifting from 2H to 4H on the JT/JL is not as smooth as it was with the JK because the front driveshaft is always turning in sync with the rear driveshaft on the JK and other non FAD front diffs.

The current FAD is electric operated, it was vacuum operated on the YJ and other older Jeeps and Dodge vehicles. It was prone to not operating (consistently) when there was a vacuum leak on the engage or disengage vacuum circuit. There were aftermarket cable FAD shifter available for the YJ and XJ.

The FAD past and present is a less expensive attempt for better MPG over manual hubs. I would love to have manual hubs on the JT like the current Ford Super Duty (lower trim levels) are available with.

 

[Harold0819]

Also with the FAD, shifting from 2H to 4H on the JT/JL is not as smooth as it was with the JK because the front driveshaft is always turning in sync with the rear driveshaft on the JK and other non FAD front diffs.

The current FAD is electric operated, it was vacuum operated on the YJ and other older Jeeps and Dodge vehicles. It was prone to not operating (consistently) when there was a vacuum leak on the engage or disengage vacuum circuit. There were aftermarket cable FAD shifter available for the YJ and XJ.

The FAD past and present is a less expensive attempt for better MPG over manual hubs. I would love to have manual hubs on the JT like the current Ford Super Duty (lower trim levels) are available with.

Exactly, great point. Eliminating the FAD will make shifting the JT much smoother.

 

[Kevin_D]

I would love to have manual hubs on the JT like the current Ford Super Duty (lower trim levels) are available with.

Or at least automatic hubs, something I have some control over.

 

[ShadowsPapa]

Also with the FAD, shifting from 2H to 4H on the JT/JL is not as smooth as it was with the JK because the front driveshaft is always turning in sync with the rear driveshaft on the JK and other non FAD front diffs.

The current FAD is electric operated, it was vacuum operated on the YJ and other older Jeeps and Dodge vehicles. It was prone to not operating (consistently) when there was a vacuum leak on the engage or disengage vacuum circuit. There were aftermarket cable FAD shifter available for the YJ and XJ.

The FAD past and present is a less expensive attempt for better MPG over manual hubs. I would love to have manual hubs on the JT like the current Ford Super Duty (lower trim levels) are available with.

AMC found that the disconnect saved a whopping 1 mpg on the Eagle so got rid of it about 1984 or so. That also resulted in a shift-on-the-fly system since there was no need to stop to let the axle shift and the t-case was synchronized (up to about 55)
I have a spare NOS FAD vacuum motor for my car as well as a pair of good used motors for the axle and t-case shifting.

 

[FLUndertaker]

It’s a solution but is also $6000 +

 

[mazeppa]

Or at least automatic hubs, something I have some control over.

I'll take automatic hubs on a JT, because the are so easy to change over to manual hubs.

 

[ShadowsPapa]

I'll take automatic hubs on a JT, because the are so easy to change over to manual hubs.

I had nothing but trouble with the automatic hubs on my F250 - THEY SUCKED!
And because I had the heavy-duty axles under the truck when I changed to manual hubs, I had to make sure I got the right ones.
It was ok, but in Iowa, a pain and you always took off with the hubs engaged in winter.

 

[Kevin_D]

I had nothing but trouble with the automatic hubs on my F250 - THEY SUCKED!

Never had any trouble with mine.

But If I was rock crawling, I'd certainly entertain the idea of removing the FAD system and putting manual hubs on the Gladiator.

 

[Harold0819]

Got my JTR back today. First off with the 5.13s and 37s the truck is very smooth upon acceleration. Trans shifts up in gear very quickly and can carry the load much better. When downshifting it doesn't drop to low and rev the engine really high or hold the gears as long as you accelerate. 8th gear is back and the truck actually can pull in 8th on the highway.
I'm happy with the FAD delete. No vibration, definitely a heavier, solid feel to the front end but not unpleasant, more like my JK. The truck shifts into and out of 4hi sooo much easier.

 

[FLUndertaker]

Got my JTR back today. First off with the 5.13s and 37s the truck is very smooth upon acceleration. Trans shifts up in gear very quickly and can carry the load much better. When downshifting it doesn't drop to low and rev the engine really high or hold the gears as long as you accelerate. 8th gear is back and the truck actually can pull in 8th on the highway.
I'm happy with the FAD delete. No vibration, definitely a heavier, solid feel to the front end but not unpleasant, more like my JK. The truck shifts into and out of 4hi sooo much easier.

Who’s parts did you end up using to delete the FAD? What did you do about the opening in the axle tube?

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