Part time vs full time 4WD?

rexinsea · **Joined:** Tue Nov 27, 2007 6:39 pm **Posts:** 2

Hello all:
I've just purchased my 05 Jeep Liberty CRD Limited about a month ago. I'm loving it so far. I've very much enjoyed the useful information on this blog both while I was making my purchase decision and now post purchase. Thank you all. Two threads have caught my eye as we enter ski season here in the Pacific Northwest. One was about snow handling and the other was about gas mileage in Full Time 4WD. What caught my eye was that everybody seemed to agree that full time 4WD was the best way to travel on snowy roads. I noticed in the gas mileage thread that many people said they shift into Full Time 4WD when the roads were wet and rainy as well. I'm new to full time (real) 4WD as I previously was a Subaru AWD guy.

QUESTIONS: When would you use part time 4WD if not on rainy/wet roads? What is the real difference between part time 4WD and Full Time? Before reading these threads I previously thought the difference was Part Time = AWD and Full Time = off road performance on rough roads/sand/really deep snow.

I guess my follow-up question will be: if I'm driving up skiing on icy/compact snow roads is full time 4WD really the right setting? Thanks for answering such a newbie question -- I'm just a bit confused and the manual that came with the rig just seems rather lacking on the subject and I'm hoping for some real world experiences/advice.

dgeist · **Posted:** Tue Dec 04, 2007 8:41 pm

rexinsea wrote:

QUESTIONS: When would you use part time 4WD if not on rainy/wet roads? What is the real difference between part time 4WD and Full Time? Before reading these threads I previously thought the difference was Part Time = AWD and Full Time = off road performance on rough roads/sand/really deep snow.

I guess my follow-up question will be: if I'm driving up skiing on icy/compact snow roads is full time 4WD really the right setting? Thanks for answering such a newbie question -- I'm just a bit confused and the manual that came with the rig just seems rather lacking on the subject and I'm hoping for some real world experiences/advice.

Part time locks the center diff preventing the front and rear axles from moving at different rates (bad on high-traction surfaces as it'll put extra strain on your gears and wheels). I use full-time it whenever I'm in the rain. If things are really bad or you EXPECT to be slipping is when part-time is a good thing. Examples are slick dirt roads, driving up a wet ramp, heavy snow where you can barely get traction, etc.

bugnout · **Posted:** Tue Dec 04, 2007 8:46 pm

Ya I thought the same thing, Full time has the conotation that it is more serious than part time. Not so...

Full time = AWD

Part time = Off road 4WD

Goglio704 · **Posted:** Tue Dec 04, 2007 11:33 pm

Well said guys. I started to respond earlier, but words failed me.

chadhargis · **Posted:** Wed Dec 05, 2007 1:31 pm

The CRD has such great torque, that I use Full Time 4WD in the rain. I was on a trip once, and I was on the interstate going up hill in the rain at 50mph. I pushed the acclerator to go around a semi and the rear tires lit up like a Christmas tree. I slowed, pull it into FT4WD, and I slipped no more.

Jeger · **Posted:** Wed Dec 05, 2007 2:18 pm

chadhargis wrote:

The CRD has such great torque, that I use Full Time 4WD in the rain. I was on a trip once, and I was on the interstate going up hill in the rain at 50mph. I pushed the acclerator to go around a semi and the rear tires lit up like a Christmas tree. I slowed, pull it into FT4WD, and I slipped no more.

That will get your attention wont it....with 55K on the stockers full time is seeing a lot of use...it will break the rears loose pretty easy now.

Jeepman56 · **Posted:** Wed Dec 05, 2007 2:27 pm

The manual says 55mph max recommended for shift on the fly into part time 4, I was wondering if that is the max speed one can drive in part time 4 as well, or can I take it on the highway? Example, we got a few inches of snow last night and this morning the highways were still a little slick (no exposed dry cement), could i use part time? Thanks for the time.

Fulltimer · **Posted:** Wed Dec 05, 2007 2:45 pm

The ONLY time I use Part Time is off road in really nasty stuff. The shift at 55 max is for going into/out of Full Time.

Terry

bugnout · **Posted:** Wed Dec 05, 2007 4:00 pm

Jeepman56 wrote:

The manual says 55mph max recommended for shift on the fly into part time 4, I was wondering if that is the max speed one can drive in part time 4 as well, or can I take it on the highway? Example, we got a few inches of snow last night and this morning the highways were still a little slick (no exposed dry cement), could i use part time? Thanks for the time.

I have driven in part time at highway speeds, but it was packed snow and ice. no pavement visible.

rexinsea · **Joined:** Tue Nov 27, 2007 6:39 pm **Posts:** 2

bugnout wrote:

Ya I thought the same thing, Full time has the conotation that it is more serious than part time. Not so...

Full time = AWD

Part time = Off road 4WD

Thanks all for the responses on such a newbie type question. I guess I just couldn't get over the naming. I still can't get my head around why "part time" = fixed 4WD but now I know.

DarbyWalters · **Posted:** Wed Dec 05, 2007 6:02 pm

Full Time indicator is a GREEN LIGHT...goes any time

Part Time is an AMBER LIGHT...use with caution

This makes it much easier to remember for those you let borrow your Jeep ect.

chrispitude · **Posted:** Wed Dec 05, 2007 6:33 pm

Related discussion in this Lost KJ thread:

CRD in snow questions

- Chris

Tinman · **Joined:** Mon Apr 10, 2006 10:45 am **Posts:** 308

This is what can happen when you run full-time on pavement!

http://www.turbodieselregister.com/foru ... rnage.html

I really like the full time/part time transfer case. I wish my truck had that.

Albert · **Posted:** Fri Dec 07, 2007 3:58 pm

Tinman wrote:

This is what can happen when you run full-time on pavement!

http://www.turbodieselregister.com/foru ... rnage.html

I really like the full time/part time transfer case. I wish my truck had that.

I don't see how running full-time caused that. Part-time on pavement - could cause something like that maby. The selec-trac t-case (with the full-time) mode is made to run on all surfaces as long as you are in full-time..

Threeweight · **Joined:** Mon May 14, 2007 5:57 pm **Posts:** 679

Post says it was running 4-hi on pavement, which I would assume means running part-time 4wd in high range with the center differential locked.

My guess is when the front and rear wheels rotated at different speeds (as in a turn) on dry pavement with no way to slip, the torque of the 5.9 diesel snapped off the weakest link.

chrispitude · **Posted:** Fri Dec 07, 2007 5:36 pm

Threeweight wrote:

My guess is when the front and rear wheels rotated at different speeds (as in a turn) on dry pavement with no way to slip, the torque of the 5.9 diesel snapped off the weakest link.

...Goodbye!

- Chris

Tinman · **Joined:** Mon Apr 10, 2006 10:45 am **Posts:** 308

Opps. My bad. That was an example a part-time transfer case running "full-time" (as in on dry pavement). I wasn't clear with my terminology. That's an example of extreme "wind up" of the transer case and is why the libby has a full-time and part-time option and why you can't run a part-time 4wd all the time. I also believe you can burn up the central differential in a full-time system in loose traction conditions like snow or sand, hence the part-time option.

Part time vs full time 4WD?

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