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post #1 of (permalink) Old 09-08-2000, 11:40 PM Thread Starter
 
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stupid 4-wheel question

I am very new to the four-wheel and jeep scene and I have a (you will probably think its stupid) question. What is the diffenence between part-time, full-time, and all-wheel four wheel drive?

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post #2 of (permalink) Old 09-09-2000, 01:34 AM
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Re: stupid 4-wheel question

Not a stupid question at all, man. MAny people are confused by those terms...and many people probably dont understand it and just dont wanna sk, so here it is in a nutshell....
Part time 4 wheel dirve is what i call REAL 4 wheel drive, it utilizes a TRANSFER CASE, which splits power from the trans evenly to both the front and rear axles. It requires shifting a lever, and almost always includes a low range. It should only be used in loose, slippery traction circumstances, unless you like drivetrain windup and trashed components, except for that quadratrac thing....dont even worry about that boat anchor. I Know CJ Dave is going to tear me a new one over that...
Full time 4 wheel drive is what a lot of the new Silverados and some Grand cherokees have. They have a differential in the transfer case, or along the driveline that allows the front and rear axles to turn at different rates to allow for turning. You can leave this type of system engageds all the time, especially if you hate getting any gas mileage whatsoever. Its an OK system, but rarely has a low range, wears out over time, the clutches, that is, and does NOT evenly split power to front and rear, which could leave you stuck.
All wheel drive is the biggest, most useless waste of gas i have seen. it puts power to all wheels, until you need it most. this is not a whole lot better than open diffs or two wheel drive. Why do you need to have power to all four wheels on a sunny day cruising at 70mph on the interstate? You dont. this is a total waste. Forget about a low range. Not getting one. If you want this, you're probably looking at a subaru station wagon...have fun!
Thats the basic idea, but its late, and i'm sure i misstated many things, and i'm tired, so i might even be wrong, if i am, someone will correct me...and now i must sleep in fear of CJDave....

mikey

98 Dodge Ram 1500 Quad Cab 4x4 Sport Plus, 5.9L 360, auto, Locked, 3.92s, BFG A/T KOs, RS9000s, RS5000 stabilizer, BedRug, tows my CJ-7!
post #3 of (permalink) Old 09-09-2000, 03:27 AM
 
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Re: stupid 4-wheel question

Thats pretty much it, in a nutshell, without getting into the rare cases such as the NP203 full time transfer case, which still used standard drive shafts and axles, and so was only disengaged at the hubs. As far as all wheel drives, they arent really of any use in a Jeep type configuration, but the Audi Quatro set up is really a very well engineered system and and has really no comparable competition in loose and or wet surface racing conditions. The Audi team for example does fantastic on courses like the Pikes Peak Race, and other rural road races that are held in Europe. I dont think youd get much argument from most wheelers about the quadra trac, Dave has done a bit of modifying and has a specific purpose for his set up,(so you might be safe from Dave after all, but if he goes off on you, you didnt hear it from me),LOL.

Jeff
89 Wrangler
"PLING" Hmm,What was that noise???....Awww probably nothing.
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post #4 of (permalink) Old 09-09-2000, 08:43 AM
 
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Re: stupid 4-wheel question

Generally speaking, the difference between "full time" and "all wheel drive" is a matter of semantics. They are basically the same thing; when it is installed on a car like vehicle that doesn't have the ground clearance or suspension to go off road, it is called "all wheel drive". When it is on a Jeep, mostly on the wagon bodied ones or pick ups (yes, they are Jeeps, too. [img]/wwwthreads_images/icons/wink.gif[/img]), it would be called "full time 4wd".

Your Wrangler YJ has a part time 4wd system, meaning that the transfer case splits the power 50% - 50% front to rear all the time it is in one of 4wd modes, regardless of traction conditions. This is a good and bad thing. It's good when you are off road and your rear tires slip; since your front will still get half the power, the Jeep might be able to get itself unstuck (if the front tires have some traction.) It's bad when your on dry pavement and in 4wd; there is no way for the drive train to relieve the stress that builds up in a turn. Don't use your part time system on dry pavement. Also be careful on snowy and icy roads. Since I know CJDave (aka the "Quadra Trac Guru"[img]/wwwthreads_images/icons/wink.gif[/img]) is going to take Mikey to task for his Quadra Trac transgression[img]/wwwthreads_images/icons/wink.gif[/img][img]/wwwthreads_images/icons/smile.gif[/img], he can explain why it is a bad idea to drive at high speeds on snowy and icy roads with a part time 4wd system. I'll defer to his expertise in that area. Good Luck!! [img]/wwwthreads_images/icons/smile.gif[/img]

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post #5 of (permalink) Old 09-09-2000, 12:21 PM
 
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Re: stupid 4-wheel question

My explanation uses some generalities- I wont deal with the specific x-cases, but this is what those terms usually mean. I am also assuming the axles have open differentials.

All-Wheel-Drive. This type of transfer case has an open differential that allows the front and rear driveshafts to turn at seperate speeds. It also has no low-range. This means that if you have ONE tire on ice and 3 tires on pavement, the tire on ice will get all the power and spin there uselessly.

Full-Time Four-wheel-drive. Once again, this transfer-case has an open or limited-slip differential and can turn the front and rear driveshafts at different speeds. It usually does have a low-range though, and quite often has an "Emergency-Drive" feature, which locks the center differential and makes the 'case perform like a Part-Time case. If you are in the same situation as above, you will be just as stuck until "Emergency Drive" is activated, then the tires on the other axle will move you forwards.

Part-Time Four-Wheel-Drive. REAL four-wheel-drive, sorta. This case spins the front and rear driveshafts at exactly the same speed, no matter what. You can have the front or rear half of the vehicle on ice and the other end will continue to provide motion. If you have lockers in both axles then all four tires will turn at the same speed no matter what.

Select-Track. The 242 transfercase used in Jeep Cherokee Classics (optional) and Limiteds (standard) is a marvel of engineering- to me at least. You can select 2wd-hi (rear-wheel drive), Full-time-4wd-hi, Part-time 4wd-hi, and Part-time-4wd-low. In general its a kick-ass 'case but I'm not sure how strong it is (anybody know what it takes to break one?)

Restoring a '74 DJ-5C [img]/wwwthreads_images/icons/cool.gif[/img] It runs [img]/wwwthreads_images/icons/smile.gif[/img] and drives [img]/wwwthreads_images/icons/shocked.gif[/img] and delivers mail...well, 2 out of 3 aint bad [img]/wwwthreads_images/icons/wink.gif[/img]
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post #6 of (permalink) Old 09-10-2000, 07:15 PM
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Re: stupid 4-wheel question

i dont know what "quadra-trac transgression" is, but it sounds like i may be in for it! hehehe!

mikey

98 Dodge Ram 1500 Quad Cab 4x4 Sport Plus, 5.9L 360, auto, Locked, 3.92s, BFG A/T KOs, RS9000s, RS5000 stabilizer, BedRug, tows my CJ-7!
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