Can anyone explain exactly how full time mode works? I was under the impression that the transfer case uses chains to transfer power, so when its in full time does the chain continue to drive the rear driveshaft and a center differential is engaged to also transfer power through a common shaft to for the front wheels? Or is the actual center differential driven by the chain?

I guess what I am getting at is do the rear wheels always receive power in Full-time mode, or is there a circumstance where only the front wheels could spin. I've personally never noticed a situation where only the front wheels spin but I've certainly noticed that Full-time is not as good as part-time in slippery snow and mud situations. The jeep seems just as tail happy in full-time as in 2wd leading me to believe that it defaults to the rear if traction is lost. I've also never experienced the plowing effect you get in a FWD car when you get into the throttle to hard.

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2006 CRD - GTB2056 turbo by Dieselguy86, Eco Trans Tune, Lift Pump, Week's, HDS Tstat, Racor Filter, ARP's, OME 790's+Top Plate, JBA 2.5", JBA UCA, Moab's+265/75R16, ARB Bull Bar, 4.10's, TrueTracs

Does this picture help? (I think its the right one)


Basically, full-time is like all-wheel-drive. Like a subaru
The "center differential" is like an open diff and allows the front and rear driveshafts to spin somewhat independantly. And like an open diff will send power to whichever end has the least traction, sort of.

But part-time makes it into a selectable locker. Locking both driveshafts together.

Part-time is probably best for ice, snow, soft sand, and mud.
Full-time is good for dry dirt roads and wet pavement.

Two footed driving is a good traction control technique when using open diffs and works with full-time too.
But that technique does not work on vehicles with traction control because traction control is supposed to do the brake application part for you.

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Sorry I think I figured this out.

I found this video of a tear down. it seems to suggest what I thought just achieved in a different way, the rear driveshaft is a always powered since the Mainshaft and the rear output shaft are one in the same. the differential for the front shaft rides on a splined section of the shared mainshaft/rear output shaft.

https://www.youtube.com/watch?v=ibY_xzCn10k

So it looks like maybe what you get is AWD until the rear end slips and then you get RWD. It doesnt look like you could ever get FWD only since the main shaft wouldnt be spinning if the rear wheels were not also spinning and the front would also have nothing turning it.

Subarus usually have a limited slip in the manuals or electronic controlled diff in the autos so they always get torque to both axles. The AWD in my 6 speed legacy GT was much better than the Full time in the jeep, obviously not taking things like ground clearance and wrangler duratracs into account. In fact my Subaru had the LSD center diff and a torsen in the rear diff so it was pretty darn good.

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2006 CRD - GTB2056 turbo by Dieselguy86, Eco Trans Tune, Lift Pump, Week's, HDS Tstat, Racor Filter, ARP's, OME 790's+Top Plate, JBA 2.5", JBA UCA, Moab's+265/75R16, ARB Bull Bar, 4.10's, TrueTracs

I disagree.
Although I believe that in full-time its biased more to the rear axle, it still behaves like an open diff.
This discussion seems to confirm http://www.naxja.org/forum/showthread.php?t=954142
But I have have never taken one apart.
Maybe someone who has can confirm.

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U.S. Army Retired

its supposedly biased 48/52 , generationally theyve gotten better with small adjustments internally, and then later with the KK's getting friction clutches

the 242 that was available in the KJ's operates like an open diff where's without two-footed driving, you actually can have a "one tire fire" if you have a tire off the ground on the front or the rear. the case wasnt designed to bias traction in that manner, it was designed more or less around that 20-30% or less difference in traction between the front and the rear and all tires having some manner of footing to the ground. i mean if it was able to properly 48/52 with a tire off the ground it would behave like a PT case, so the biasing is relative to the conditions being within the engineering specifications.

the KK's 242 has friction clutches similar to what the trac-loc differential uses, which also means, they're eventually going to wear out

i don't know for absolute certain, but i 'think' jeep went to a 242 with friction clutches in the KK , at least in part, due to better functionality (not overloading) the traction control systems in use in the KK's that weren't offered in the KJ's, but that's just a bit of speculation. it may have been more as them phasing out the 231 in favor of the 242 as less likely to cause problems with the vehicles typical driver, which isn't us, it's "those other" jeep drivers lol.

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i also think the 242 from a drivers standpoint gets mistaken for the 247 of the WJ's quadra-drive, I, II / quadra-trac I,II 247/147/245
which was an era of full-time/part time/ 4-Low cases that used some sort of hydrolic pump and clutch pack to gradually bring the non-slipping axle up to the same speed as the slipping axle

and by looking at the shift lever on that era WJ they're basically identical to the 242's. but as far as technical funcionality they couldn't be more different, but resulted in the same sort of driveability benefits

then there was the 249 in the grand cherokee which actually was an all wheel drive system using a viscous coupling , just backwards from the function of say the subi or mitsu awd. when the rear wheels slipped the VC directed torque towards the front axle

there were a lot of approaches to the "full-time" solution just over a period of say 20 years across the same platforms that resulted in our vehicles

either novak or NV has a pretty cool animated thingy that shows how each transfercase works, but it may or may not show generational differences such as whats found between the 242 in the KJ and 242 in the KK

but it may, i dont recall

_________________
03 Renegade (Black)
177k miles 3.7L gas - 45RFE
Command Trac / 4.10s
Lift: ft. 790+ rr. JBA4+
The last of the TrailReady Front&Rear Bumpers and TR Rock Rails
Jarhead Offroad light covers
31x10.5R15 RedLetter Grabbers on Blackrock Dunes
L.O.S.T #KD098632