Full time vs part time

itbrokeagain · 09-29-2009, 08:00 PM

Just picked up a xj with full time and part time 4wd. What is the difference? If I am wheeling in full time what will happen?

KargoMaster · 09-29-2009, 09:21 PM

Where are you getting the part time and full time part??

Here's my take on this generic idea... (and I'm no XJ guy)

Full time 4wd means the front driveshaft always spins.

Part time 4wd means the front driveshaft will not spin in 2wd (usually accompanied by lockouts)

You can have one or the other... not both.. but there are also wacky things like a tcase locking device that will force a 50/50 split of power front/rear.... guess I'm still confused on where you're getting the idea that it has both...

jeeptech77 · 09-29-2009, 09:32 PM

in a xj the transfercase has what is known as a viscus coupling it is suppost to allow limited slip between front and rear driveshaft
ideally for snow and on pavement use
this is known as part time use

full time operation is when the differential in the transfercase is locked together ( kinda like a spool ) but disenguageable

the older chevy ford dodge had lockouts so the vehicle would not move in part time just like a open diff with wheel off the ground

itbrokeagain · 09-29-2009, 10:31 PM

But does it make a difference in a offroad situation? Now I would normally leave it in low but I am just curious.

The t-case positions are

2wd
4full time
4part time
N
4lo

Hope Springs Hauler · 09-29-2009, 11:48 PM

From my test drives of XJs, it seems to me that the viscous coupling is active when it is in 4wd Fulltime. This would be the setting to use for slick onroad situations.

Switching to 4wd part-time locks the coupling and it becomes like a traditional transfer case.

The danger in wheeling in "fulltime" is placing a lot of stress on the t-case if 1 wheel were to spin and the rest have great traction.

WrenchMonkey · 09-30-2009, 03:11 AM

Quote:

Originally Posted by jeeptech77

in a xj the transfercase has what is known as a viscus coupling it is suppost to allow limited slip between front and rear driveshaft
ideally for snow and on pavement use
this is known as part time use

full time operation is when the differential in the transfercase is locked together ( kinda like a spool ) but disenguageable

the older chevy ford dodge had lockouts so the vehicle would not move in part time just like a open diff with wheel off the ground

Close... Just exactly backwards.

The standard XJ case is the NP231. 2WD-4HI-N-4LO.

Engaging 4HI or 4LO locks the front and rear driveshafts together (actually chains them together, whatever...) Great for off-road, not so much on-road.

The optional cases (NP242 et al) have the viscous coupling, and the positions you list: 2WD-4FT-4PT-N-4LO

The 4PT works like the 231's 4HI: Positive engagement.

The 4FT is the one that allows some slip between the 'shafts. Great for on-road, iffy-traction situations.

You already know to use 4LO on the trail.

Robert

blazerbrad · 09-30-2009, 09:55 AM

As mentioned above, 4 full-time is the same basic idea as AWD and you can use this anytime on any condition. However, there is no viscous coupling or any type of limited slip in regards to transferring power between the front and rear tires. The transfer case functions as an open differential between the front and rear axles (we did testing on vehicles equipped with this transfer case for years, and I just glanced through a factory service manual to verify)......no clutches, no viscous coupling, just an open diff....at least for the Jeep/Dodge/Chryler versions.

This means that you can have a "one wheel peel" going on when in full-time 4wd mode, and I've personally seen this. Again, we intentionally performed a durability test on a wetted uphill grade where a vehicle took off at wide open throttle from a stop, which caused only the left front wheel to spin like mad. Also, if you pulled either the front or rear driveshaft the vehicle would not move unless in 2wd or locked in 4wd.

Several versions of this transfer case were used over the years. Included are "4 position" and "5 position" versions in both manual and electronic shift models. The 5 position versions had 2 hi, 4 FT, 4 PT, N, 4 lo. The 4 position versions eliminated the 2 hi option, normally electronic shift, and where used in heavier vehicles like the V-8 Durangos. This version was called the 244. They also tried a 144 version that eliminated low range, but I don't know if that ever made it into production. (Note the name changing from "2" to "1" which denotes 2 gears, hi and lo range, to just 1 gear).

Jeeps did use other versions of transfer cases with various forms of limited slip and viscous couplers including the 249 (optional in the ZJs) and the 247 (optional in the WJ's). Both of these had a direct drive to the rear wheels, and the viscous coupling applied power to the front as needed.....meaning you could pull the front shaft and they would deliver power to the rear wheels with no slippage.

itbrokeagain · 09-30-2009, 09:08 PM

Ok sounds good. So how does this t-case hold up?

And blazerbrad got me thinkiing about something else. Does this mean that in 4fulltime because of a center diff, that it will be either front wheel or rear wheel drive depending on traction?

09-29-2009, 08:00 PM	#1
itbrokeagain Just Empty Every Pocket - CORE Member - Join Date: Feb 2007 Location: Amelia Posts: 1,435	Full time vs part time Just picked up a xj with full time and part time 4wd. What is the difference? If I am wheeling in full time what will happen? __________________ 91 fj 80 on 37 Nitto Muds with a 10k winch. Cage and sliders coming soon.

09-29-2009, 09:21 PM	#2
KargoMaster Cleaning off the rust... Join Date: Jan 2007 Location: Cincinnati, OH Posts: 1,009	Where are you getting the part time and full time part?? Here's my take on this generic idea... (and I'm no XJ guy) Full time 4wd means the front driveshaft always spins. Part time 4wd means the front driveshaft will not spin in 2wd (usually accompanied by lockouts) You can have one or the other... not both.. but there are also wacky things like a tcase locking device that will force a 50/50 split of power front/rear.... guess I'm still confused on where you're getting the idea that it has both... __________________ brad 5.0L \| 435 \| 203 \| 300 \| 4.10 \| 39.5 Buildup BACK underway...

09-29-2009, 09:32 PM	#3
jeeptech77 jeeptech77 Join Date: Aug 2007 Location: cincinnati Posts: 12	full time in a xj the transfercase has what is known as a viscus coupling it is suppost to allow limited slip between front and rear driveshaft ideally for snow and on pavement use this is known as part time use full time operation is when the differential in the transfercase is locked together ( kinda like a spool ) but disenguageable the older chevy ford dodge had lockouts so the vehicle would not move in part time just like a open diff with wheel off the ground

09-29-2009, 10:31 PM	#4
itbrokeagain Just Empty Every Pocket - CORE Member - Join Date: Feb 2007 Location: Amelia Posts: 1,435	But does it make a difference in a offroad situation? Now I would normally leave it in low but I am just curious. The t-case positions are 2wd 4full time 4part time N 4lo __________________ 91 fj 80 on 37 Nitto Muds with a 10k winch. Cage and sliders coming soon.

09-29-2009, 11:48 PM	#5
Hope Springs Hauler Join Date: Jul 2008 Location: Hamilton, OH Posts: 431 Images: 16	From my test drives of XJs, it seems to me that the viscous coupling is active when it is in 4wd Fulltime. This would be the setting to use for slick onroad situations. Switching to 4wd part-time locks the coupling and it becomes like a traditional transfer case. The danger in wheeling in "fulltime" is placing a lot of stress on the t-case if 1 wheel were to spin and the rest have great traction. __________________ 1988 Suzuki Samurai on propane FJ 40 axles (4.10) 5.14 tcase 36" TSL SX

09-30-2009, 09:55 AM	#7
blazerbrad - CORE Member - Join Date: Feb 2007 Posts: 831 Images: 6	As mentioned above, 4 full-time is the same basic idea as AWD and you can use this anytime on any condition. However, there is no viscous coupling or any type of limited slip in regards to transferring power between the front and rear tires. The transfer case functions as an open differential between the front and rear axles (we did testing on vehicles equipped with this transfer case for years, and I just glanced through a factory service manual to verify)......no clutches, no viscous coupling, just an open diff....at least for the Jeep/Dodge/Chryler versions. This means that you can have a "one wheel peel" going on when in full-time 4wd mode, and I've personally seen this. Again, we intentionally performed a durability test on a wetted uphill grade where a vehicle took off at wide open throttle from a stop, which caused only the left front wheel to spin like mad. Also, if you pulled either the front or rear driveshaft the vehicle would not move unless in 2wd or locked in 4wd. Several versions of this transfer case were used over the years. Included are "4 position" and "5 position" versions in both manual and electronic shift models. The 5 position versions had 2 hi, 4 FT, 4 PT, N, 4 lo. The 4 position versions eliminated the 2 hi option, normally electronic shift, and where used in heavier vehicles like the V-8 Durangos. This version was called the 244. They also tried a 144 version that eliminated low range, but I don't know if that ever made it into production. (Note the name changing from "2" to "1" which denotes 2 gears, hi and lo range, to just 1 gear). Jeeps did use other versions of transfer cases with various forms of limited slip and viscous couplers including the 249 (optional in the ZJs) and the 247 (optional in the WJ's). Both of these had a direct drive to the rear wheels, and the viscous coupling applied power to the front as needed.....meaning you could pull the front shaft and they would deliver power to the rear wheels with no slippage.

09-30-2009, 09:08 PM	#8
itbrokeagain Just Empty Every Pocket - CORE Member - Join Date: Feb 2007 Location: Amelia Posts: 1,435	Ok sounds good. So how does this t-case hold up? And blazerbrad got me thinkiing about something else. Does this mean that in 4fulltime because of a center diff, that it will be either front wheel or rear wheel drive depending on traction? __________________ 91 fj 80 on 37 Nitto Muds with a 10k winch. Cage and sliders coming soon.