Can anyone explain the difference? What is actually going on with the tranny in the different modes?

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2006 Liberty CRD Limited

This is a function of the transfer case, not the transmission... The way I understand it is:
full time has an open center diff which allows power to be distributed unevenly from front to back.
part time has a locked center diff which distributes power evenly front and back.

similar to an open and locked rear differential.

Jeep has a nice flash on the selec trac
http://www.jeep.com/4x4/

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1989 Dodge Raider
05 Jeep Liberty CRD

The tranny works the same in either mode, the transfer case however is working differently. In full time there is a differential working in the transfer case that is distributing the power to the end of the rig that has the most traction. Works like a Subaru, and all the rest of the all wheel drive cars. In part time the transfer case is fully locked up, power is being distributed front and back all the time, the problem with this is that the tires on your rig are not identical in size so as you roll down the road one end is invariably running a little faster than the other end. This is not OK as there is little slop in the drive train, so the gears start binding. When they bind the rig doesn't roll well, a second later your dragging one end of the rig around like you have the brakes on, a microsecond later you may be looking at oil on the road along with pieces of your transfer case. You don't use part time high or low on a surface that has good traction for that reason.

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No one knows as much as all of us.

The easiest way to remember which one is for street and which one is for offroad is by the color of the indicator lights. In FullTime it lights up in GREEN...Green stands for go on any surface. In PartTime is lights up in AMBER...Use with Caution on offroad only.

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Founder of L.O.S.T.
2006 CRD Sport
Mods: GDE Hot Tune w/ 364#@2000rpm/Air Box /3" Str8 Exhaust/ASFIR Alum Skids/245-75R-16 Cooper STT PRO/OME LIFT w/Clevis & 4 Spring Isos/AirTabs/Rigid 10" S2 LED/4xGuard Ctr Matrix Bumper
Drag Strip:Reac=.1078_60ft=2.224_1/8=10.39@64.8mph_1/4+16.46@80.8mph

I run in Full-Time (green) mode all the time, unless I'm off road. Keeps everything more sure footed on the street in stickey situations, and according to jeep, it decreases wear on the drive line components as well.

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--Greg
2005 CRD Sport in white
2.5" Daystar Lift Kit
245/75/16 Maxxis Buckshot Mudders

I only wish they had sequenced the position of the modes more realistically: ie 2wd,Full-time, part time, N, low. Instead the current order (with part-time first),is not-intrinsically obvious. Plus,they could try better names.

How about 4-high on-road, 4-high off-road?

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2005 Liberty Sport CRD w/all the fixings
Elephant Hose, MAF (ORM), Amsoil Airfilter, nice when I get to drive it
1 EGRreplacement, but never again.
99.5 FrankenJetta TDI (R.I.P.): being turned into diesel hybrid!
99.5 Replacement Jetta TDI: deal of a lifetime, EHM, some other stuff

Reduces wear vs part-time, correct? 2wd will result in minimum wear as the front end is isolated from engine torque.



4-Hi is the same story as 4-Low except that the gearing of the transfer case is higher (or, normal as 4-low decreases the final drive ratio). In other words, you shouldn't use it on any surface that provides good traction but you can drive quite a bit faster than when in 4-Low.

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03/15/2006 Jeep Liberty Limited CRD w/86,000 mi. Engine lube pump, Provent, V6 airbox mod, Magnaflow, gauges, Amsoil all around, & Wix air filter. Sunroof drain blocked on receipt, stubborn fuel leak at 2200 mi, 3 jammed windows, & 1 bad alternator decoupler, but it's still a keeper!

My bad, I should not have used the term "high" as that is what is used in the other version. So I guess my terms only made confusion worse..hmm.
The original post was for the difference of 4 part time vs 4 alltime vs 4 low. Since I made things worse, I will clarify, 4 part-time and 4 low are the same thing, except the gearing is lower. 4 full time as the front and back differencial.

So what I meant is that they could use other names (and sequences) for:
a) 2 wd
b) 4 Part Time (switch position to "c" and change name to something like "4 fast off-road only")
c) 4 Full Time (switch position to "b" and change name to something like "4 fast on-road")
d) nuetral
e) 4 Low

To be fair, Jeep dearing names always were confusing. They might be trying to carry on the tradition!

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2005 Liberty Sport CRD w/all the fixings
Elephant Hose, MAF (ORM), Amsoil Airfilter, nice when I get to drive it
1 EGRreplacement, but never again.
99.5 FrankenJetta TDI (R.I.P.): being turned into diesel hybrid!
99.5 Replacement Jetta TDI: deal of a lifetime, EHM, some other stuff

I agree that the transfer case mode names are confusing. It took me a while to get it straight in my head because 4 part time seems more logical for allwheel drive than 4 full time and the order of modes on the transfer case is out of order. The color of the dash lights were definitely a help when I first bought my jeep.

My suggestion would be to re order them, and give them names 2WD, AWD, 4WD HI and 4WD LO.

I'm applying for the ergonmics position at DC next week

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2005 CRD "Ol' Blue"
Red Ryder carbine-action, two hundred shot range model air rifle with a compass in the stock and this thing which tells time.
My build page- RL Komodo Rear and TJM Front Bumper, armored, lifted, JBA Steel D30, 4.10s and ARB air lockers.

Whenever I'm driving in a snowstorm or something where I definantly need 4wd all the time I always select Part Time 4wd. The day after a storm when I'm constantly transitioning between snow covered, wet and dry roads I select Full Time because as stated earlier it allows slippage between the front & rear ends which prevents binding.

The reason I simply dont use Full Time all the time is because I actually burned out the clutch in the transfer case of my 2000 Sierra by doing this. There is a clutch in the transfer case for this full time feature and it is a wearable part.

I run full-time when I am driving in the rain at 100mph. Really helps allot at that speed.

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No longer a CRD or Jeep owner. Selling everything I have, needs to go as I need the room for a project.

100 mph in the rain !!!.. are you serious... doesn't that seem just a tad excessive.. I don't think I'd do 100 mph in dry conditions with my Jeep.. brave you are..

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Emilio

2006 Liberty CRD Limited
Viper remote starter / alarm
Rocky Road 2.5" Lift
"Rubicon" 16" Wheels
Goodyear Wrangler MT/R - 245/75/16 -
EDGE Products CRD EZ Module

Not too much longer...... First half way decent sized puddle and you're gone.

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2005 CRD Sport
Mods: Glasspack, OME HD Struts & Springs, 2" Daystar lift,
255/70/16 General Grabber AT2's on MOAB's
ORM&EHM with great success!
TJM T17 Bumper, 50W KC HID's

Notice his location. On the autobahn he might get run over if he didnt go at least something close to that.

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It may be that your only purpose in life is to serve as a warning to others.

06 CRD Sport
Built 5/11/06
Jeep Green
Rocklizard diff cover
V6 Airbox

When I was young & stupid, my brother & I spent a few weeks driving the autobahn in a rented Mercedes. Kept it well above 100 most of the time. What got me was that I still had to keep keen watch of the rearview as cars (almost always Audis for some reason) would "spontaneously" appear behind us, and pass as if we were standing still. It's crazy driving. It's not right to fear being rear-ended when you're doing 100.

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03/15/2006 Jeep Liberty Limited CRD w/86,000 mi. Engine lube pump, Provent, V6 airbox mod, Magnaflow, gauges, Amsoil all around, & Wix air filter. Sunroof drain blocked on receipt, stubborn fuel leak at 2200 mi, 3 jammed windows, & 1 bad alternator decoupler, but it's still a keeper!

True, except when its raining. Being from germany I can tell from experience that if it is raining hard you do not wanna drive 100mph, regardless of 4wd. I mean its just common sense, when the streets are wet the faster you go the more you start to hydroplane. Everybody drives "slow" on the Autobahn when its raining.

edit: Thats what they make the right lane for, so you dont get run over! In germany its the law to drive on the right lane unless your passing, and almost everybody does so. Haha whats funny is that germans always get really pissed of when they have to drive a Autobahn thats close to US Airforce bases. Because what you will always see is someone going 75mph in the left lane! No offense people, it just proofs to be true everytime.

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2005 CRD Sport
Mods: Glasspack, OME HD Struts & Springs, 2" Daystar lift,
255/70/16 General Grabber AT2's on MOAB's
ORM&EHM with great success!
TJM T17 Bumper, 50W KC HID's

Autobahn has a better safety record then any Interstate in in the US. I hate the idiots that drive in the "fast lane" and will not pull over. IL will give you a ticket for that, and MO use to back in the 70's, but seldome does any more.

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91 MB 300D 2.5L Turbo. Her's

05 MB E320 CDI. Mine

I'll move out of the left lane if there is somebody behind me wanting to go faster and there is somewhere for them to go. If I'm stuck behind a guy in the left lane, the guy behind me is stuck too. If he tries to pass me in the right lane and get in my following distance, he better be able to outrun me.

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Matt B.

05 Limited CRD. Bought it new. 112k on the clock now.

GDE Eco-tune, rear differential drain plug (drilled and tapped the pumpkin), transmission pan drain plug, Fumoto oil valve, fuel filler neck restriction removed, front hitch, Hayden fan clutch, Sears P1 battery since 08, Mobil 1 5w40, 5 volt glow plugs, DIY timing belt at 109k

I'm stupid, I was running it part time in the rain etc. at times and used Full time when I was off-road. I told my wife to run it on the first setting(part-time) when there was patches of snow, she mentioned that it was binding up and I thought she put it in the wrong mode. it turns out she did put it in the wrong mode because of me. Oops.

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Feb/2006 Silver Sport 4x4 CRD