Re: 2008 Rubicon

Why does the front driveshaft turn when in 2wd?
I think the front hubs are always engaged therefore making the driveshaft and gears spin all the time.
I also think the 4wd is controlled electronically in the transfer case.
Doesn't this cause excessive wear on the front drivetrain?
Doesn't this reduce fuel economy?
Can this be remedied by installing manual locking hubs?
What happens to the factory locking hubs if you install manual locking hubs?

Thanks for the help if anyone can give me some info.
Dan

 

While I haven't had time to specifically look at the JK system yet (only had mine for 8 weeks)... if it's like all other Chrysler 4x4s of the past decade then there is NO disconnect of any type in the front diff. or hubs. Everything is a solid, permanent connection. The only disconnect is at the t-case itself.

Pros: MUCH more reliable.

Cons: 0.5 MPG decrease. Slightly lower life of front end parts.

I'll take the trade-off any day of the week. The "auto" hubs of yesteryear and electronic nannies in the t-cases SUCKED and were extremely prone to failure.

 

They have hub kits if you have 1.5k to spend.

 

Yes, the front hubs are always engaged, so everything spins whenever the JK is moving.

The 4wd is not electronically controlled. The lever mechanically positions the t-case internals for each mode.

Having permanently engaged front hubs doesn't cause excessive wear on the front axle components, any more than the rear axle suffers from excessive wear.

Those who have installed selectable hubs have reported little to no gain in fuel economy; certainly not enough to have them for that reason.

There is normally nothing to be "remedied" by installing selectable hubs. It is a good option to have if you break an axle shaft, or have an excessive front pinion/drive shaft angle.

The factory hubs are completely replaced when you install the selectable hubs.

 

Spyntec, by Solid Axle.

$1450 for the kit. And it also changes the bolt pattern from 5x5 to 5x5.5, so you need new rims or wheel spacer/converters also.

There was some talk about another company coming out with some manual hubs, but I don't recall who it was. You can also go to manual hubs if/when you upgrade to a PR44 or any of the D60 axles.


Trash them?


That's what they say. I ran my front end with no guts and no driveshaft (no gears/axle shafts, just a big hole where the pinion was) for several months and didn't notice any mpg increase. In-town only, though. It's very possible that freeway mpg's would have improved.


More wear than manual hubs? Sure. Excessive wear? Guessing they wouldn't be using auto hubs from the factory if they caused 'excessive' wear.

 

If you replace your factory front driveshaft with one of those double cardon types then it would be a good idea to go with the hub disconnect kit at the same time to avoid the exploding tcase syndrome.

 

Please 'splain that to me, thanks

 

People are having issues with transfer cases exploding. One semi-common denominator is it happening while running aftermarket double cardan shafts. The thought is that the pinion angle is off enough to cause some vibes, then at some certain freeway speed you get some type of harmonic in the joint that transfers into the tcase and kapow! Stop the shaft from spinning (ie - manual hubs), and you lessen the chance of it happening. (I believe there was one report of a toasted tcase from someone running manual hubs, so it is not a foolproof theory, but there are indications that double cardans and driveline angles are a factor...)

 

Another pro regarding the permanently locked hubs on the JK is that since the axle shafts, diff gears and front driveshaft are always turning when the vehicle is in motion all these components and their associated gears, bearings and seals are being constantly lubricated. An issue with the older vehicles with manually locking front hubs that were not used in 4WD very much is that all these front axle components would sit for many years without use and could sieze, suffering accelerated wear or sudden mechanical failure the first time the hubs were locked (assuming it wasn't one of those t/cases that only offered 4-high or Low and no 2WD option in which case both drive shafts would be turning anyway).

 

With the aftermarket shafts that use the standard double cardon shaft there is a ball bearing in the middle of that unit. I work on Ford trucks and we get to replace a tcase once in awhile after that same type of failure when those guys leave there hubs engaged instead of unlocking them or leaving them in auto. There is a new type of double cardon that is designed for higher angles, don't remember the name of it, but it has done away with that high failure middle ball joint in the middle of the double cardon. It came on the market 3 or 4 years ago I think. I would do some research and find that type if I were going to replace my shaft and not have the unlocking hubs.