I doubt it's much of an impact on mpg at all which is why they dropped it. As far as the caster and vibrations, the rzeppa joints are very tolerant of angle mismatches. If you go to an aftermarket ujoint shaft then you'll likely have issues. You can buy the actuator motor and install a switch to make your FAD functional if you run into issues.
Portals so you can run low enough lift to not have vibration issues even with 40s.
I really like having the fad. Yes. If I had aftermarket axles, Iād do locking hubs instead. But some way of preventing that driveshaft from rotating needlessly. I donāt care about the gas mileage, as itās no long my daily, and I doubt it would be noticeable anyway. Itās the wear and tear.
Lifted the rezeppa joints donāt survive. Iāve murdered two of them. I finally put a 1350 on. Those are not happy at high speeds so Iām happy I have the disconnect.
I think the wear and tear argument is ridiculous anyway. It's not like there's load on any of the front drive components even without the FAD in 2wd. What wear are you saving? The pinion bearings? Everything else still rotates as the stub shafts are attached to the wheels. Further the rear end is always under load and yet you aren't burning through rear ends every 20k miles? How much wear are we really talking about? At 200k miles you may need to rebuild the rear but the front will still have a few miles left on it...if it hasn't broken or bent at the FAD housing by then? It has its advantages for drive shaft angles that aren't great (although if you screw that up too bad what do you do when it's snowing on the freeway). Given the choice I'd take the strength of a single piece axle tube on the passenger side.
Only the driveshaft and transfer case output. As far as Iām concerned, thatās the wear. No biggie if not lifted. But lifted those oem driveshafts canāt handle it.
My JT has been lifted since 1100 miles and on 37s. It's at 53k miles now. The front driveshaft is still fine. It's drooping too far that kills them. With the mojave shocks and shock extensions mine doesn't droop far enough to bother it. Yes I'm giving up a fair amount of downtravel, but we have the wife's JLUR for the extreme rock trails. Works great on moderate to hard trails and out in the desert at speed which is my main concern for this truck. If the rzeppa joints failed quicker from simply turning on the road in 2wd, the rear wouldn't last.
The rears donāt handle lots of droop great either. But a carrier bearing spacer helps. Mines also been lifted since close to new on 37ās. The front angle is severe even at ride height. You pretty much get a choice between spring bow and driveline angle unfortunately. I chose spring bow since the driveshaft doesnāt move unless Iām in 4wd.
