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Unread 02-21-2003, 07:31 PM   #1
Igorot_Jeeper
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Part time and Full Time 4WD Difference

Can someone please tell me the difference between the two. I want to know how they function differently from one another and what is going on with my jeep when I use either of them. I also want to know when should I use either of them. The manual says part time 4wd is for slippery surfaces and full time 4wd is for all surfaces, can someone add to that. Thanks in advance.

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Unread 02-22-2003, 03:37 AM   #2
ChrisinVA
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Ok, here's the skinny.

Part time locks the front and rear driveshafts together. Basically this gives you '2 wheel' drive...one front, one rear. If you were to put the two right wheels on teflon, they would spin and get you nowhere.

Full Time is a little different, depending on what guts you have in the transfer case. Let's say you have the Selec-Trac from the very first ZJ's with the 4.0. Those were what's called an 'open differential', meaning all 4 wheels are given 25% of the available engine torque, until one wheel slips. Then that one wheel gets 100% torque, and spins, getting you nowhere. This function is nice because it *does* take more to break loose a wheel with 25% than 50% like with rear wheel drive.

The later models with the V8's, etc took it a step further and added what's called a 'viscous clutch' to the transfer case. What this does (when functioning) is sends power "from the wheel that slips to the wheel that grips" ala Subaru, etc. Unfortunately, Chrysler felt it necessary to delete the PT function except for the low range which locks the axles together.

Now, when to use each. Full Time can/should be used all the time. Period. Dry/wet/snowy..whatever.

Part Time can be used when the going gets hairy enough that FT just isn't cutting it, like offroading or snow/ice. It can also be used in heavy rain, despite what others may say. Do *not* however have it engaged on dry pavement, especially when turning. Wanna see aluminum explode?

Hopefully this helps.
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Unread 12-14-2014, 11:30 AM   #3
blancawelder
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When I put my 1990 jeep Cherokee in "part time" 4x4 and turn the Jeep, I get the "bucking" reaction. In "full time" 4x4 turning is easy and the wheels are allowed to slip a little.
basically Chrysler doesn't know the difference between part time and full time. Even the placard on the drivers visor states, "Part time for loose gravel or snow, do NOT use on hard surfaces. Full time for ALL road surfaces".
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Unread 12-14-2014, 01:03 PM   #4
Mickey_D
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The "Part Time" and "Full Time" are descriptions of when to use them, not their function.

Part Time - use it part of the time, like on snow/ice or when wheeling. Not to be used all the time.
Full Time - can be used under all driving conditions. Can be used all the time.


Please remember that when the ZJ came out they were most likely targeted at soccer moms and business execs. They were most definitely NOT aimed at off road enthusiasts. If they were aimed at us, they wouldn't have A/C, cruise control, power windows, alarm systems, leather interiors. They would look like a WWII era Willys MB.

Now saying that, try to think like a soccer mom. She's not going to be thinking, "oh, part time means the drive shafts will not bind up and grenade the planetary gears in the differential because the system is only using four wheel drive part of the time.". Nope, she's gonna be thinking, "oh part time means I should only use it part of the time".

Gotta dumb instructions down to the lowest common denominator. You're over thinking it if you think part time means it's only engaged part of the time...
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Unread 12-14-2014, 03:24 PM   #5
kg6mov
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11 years dead! 11 years! Give me a break.

Your only post on this forum is to revive an 11 year dead thread about a vehicle you don't have?
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Unread 12-15-2014, 05:32 AM   #6
GRAFIK_ZJ
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Quote:
Originally Posted by kg6mov View Post
11 years dead! 11 years! Give me a break.

Your only post on this forum is to revive an 11 year dead thread about a vehicle you don't have?
Bahaha GET EM!!
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Unread 12-15-2014, 06:18 AM   #7
PolkaPower
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Quote:
Originally Posted by blancawelder View Post
When I put my 1990 jeep Cherokee in "part time" 4x4 and turn the Jeep, I get the "bucking" reaction. In "full time" 4x4 turning is easy and the wheels are allowed to slip a little.
basically Chrysler doesn't know the difference between part time and full time. Even the placard on the drivers visor states, "Part time for loose gravel or snow, do NOT use on hard surfaces. Full time for ALL road surfaces".
I'm glad we are finally figuring this out.
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Unread 12-16-2014, 10:05 AM   #8
blancawelder
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30 years ago, I had a 1948 CJ-2A, 4 cylinder "Go Devil" engine, 3 spd, 2 spd xfer case, 5.38:1 gears. I could idle up steep 4x4 trails and even get out and walk beside the Jeep.
Every 4 wheel drive I owned after the '48, (except my Cherokee), Ford, Chevy, Toyota, Part Time means Part Time and Full Time Means Full Time. My Cherokee is the first Chrysler I've ever owned. Are the new Jeeps just as confusing?
I take my Cherokee into some rugged country and I'm beating the crap out of it. Gonna start looking for another old Willy's CJ for the high Country and use my Cherokee for flat land driving.
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Unread 12-16-2014, 11:42 AM   #9
superj
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the new wranglers suck. they are worse. i cannot comment on the cherokees and stuff that are new, i wont get one.

i like the 80s and 90s jeeps (wranglers, cherokees, grand cherokees, comanches) because they were nimble and comfortable with tons of power. we just sold our four door wrangler because it was huge and plastic, got terrible gas mileage, and had zero power. it was a pain to work on, also. i will take a jeep any day of the week for anything, as long as its older then 2006 and normally drives in rear wheel drive.
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