Jeep 4x workings - JeepForum.com
Search  
Sign Up   Today's Posts
User: Pass: Remember?
Advertise Here
Jeep Home Jeep Forum Jeep Classifieds Jeep Registry JeepSpace Jeep Reviews Jeep Gallery Jeep Clubs Jeep Groups Jeep Videos Jeep Events Jeep Articles
Go Back JeepForum.com > Models > Jeep Wrangler Forums > YJ Wrangler Technical Forum > Jeep 4x workings

Introducing MONSTALINER™ UV Permanent DIY Roll On Bed LineOfficial Chassis Saver Rust Preventive Truck & Auto UnFS: 2007-2013 Jeep Wrangler "HALO" Angel Eye Kit

Reply
Unread 06-10-2004, 10:34 AM   #1
mikeyc
Registered User
 
Join Date: Jun 2003
Posts: 58
Jeep 4x workings

There are alot of different 4x4 and awd systems out there. Jeep alone make several types. Could someone explain to me how the 4x system on a 94 Sahara works. I don't have rear lockers, just a plain 4x that would be on a stock sahara. What gets the power, how much, what happens when slipping occurs, etc?

If this has been covered and I just couldn't find the previous post could you point me to it. Thanks.

MikeyC>

__________________
94 Sahara
Stocky McStock Stock
Looking to do some work to it once I get out of school and have some money...
mikeyc is offline   Reply With Quote
Unread 06-10-2004, 11:06 AM   #2
prossett
Registered User
 
Join Date: Jan 2004
Location: The oasis city of Al Ain, where the red sand dunes of the UAE meet the craggy mountains of Oman
Posts: 364
Check in the FAQ, and then do a search for 4x4* or 4WD* and you'll find all you could possiblt want to know. If then you have a specific question, feel free to post it here.
__________________
International Jeep Club, Member No. 1 - Canadian living in the United Arab Emirates [URL=http://www.jeepforum.com/forum/showthread.php?t=81649] -JOIN CLUB HERE-[/URL]

[COLOR=white]White Jeep [/COLOR] Club Member 33
prossett is offline   Reply With Quote
Unread 06-10-2004, 11:26 AM   #3
CanukYJ
Registered User
 
Join Date: Sep 2003
Posts: 2,331
I’ll throw in the quickest explaination of this system: 4wd both axles get 50% of available torque, but with open diffs at front and rear if 1 rear tire slips ALL available power is ‘transferred’ (invisibly by nature of course) to the front axle, if 1 front tire slips all power goes to the rear, if 1 rear and 1 front slip then you do not move at all.
__________________
My jeep has only ever killed 3 things, a cat, a deer, and my wallet. What's the problem officer?

1992 Red YJ. Lifted, locked, and loaded with beer (Disclaimer: This doesn't mean said driver endorses drinking and driving, please enjoy alcohol responsibly and do not operate any vehicle of any kind, thank you....)

Thanks to the price of gas here ($4.25 a gal) I just bought a mountain bike, 0" of lift, 0" of travel, MT's, locked rear axle, oh yeah, it's the sh#$.
CanukYJ is offline   Reply With Quote
Unread 06-10-2004, 08:30 PM   #4
sentinal02
H2 Recovery Team Member
 
sentinal02's Avatar
1992 YJ Wrangler 
 
Join Date: Feb 2003
Location: New York
Posts: 6,688
Quote:
Originally Posted by mikeyc
There are alot of different 4x4 and awd systems out there. Jeep alone make several types. Could someone explain to me how the 4x system on a 94 Sahara works. I don't have rear lockers, just a plain 4x that would be on a stock sahara. What gets the power, how much, what happens when slipping occurs, etc?

If this has been covered and I just couldn't find the previous post could you point me to it. Thanks.

MikeyC>
WARNING! BOOK AHEAD! Jeep 4wd 101. lol Sorry if this seems a little more basic then you wanted but you did ask.

Ok, the 94 sahara, and just about all jeeps for that matter use a part time 4wd system. I'm sure you've seen the short little stick on the floor of the jeep just in front of where the cneter console is or would be? that's the selection lever for the transfer case. In the stock form, the case has 4 possible positions. 2Hi, 4Hi, N, or 4low. When the case is in 2hi, only the rear wheels of the jeep get power. The front wheels and the front drive shaft just free wheel. In 4hi, you have both axles getting power, like Canuk said, split pretty much 50/50. N is obviously Neutral, however it's not the same as putting your tranny in neutral. The transfer case itself has it's own neutral, so you could technically leave the jeep in gear idling if your case is in neutral (that's a good way to warm up your transmission in the winter time BTW. put the jeep in 2nd or something, the case in neutral and let it warm up like normal. helps ease the hard shifting on those really cold nights). 4low is the same setup as 4hi with one critical difference: there's a 2.72 to 1 gear reduction on low range, accomplished by the planetary gears in the transfer case itself. This reduction increases the torque applied to the wheels from the engine almost 3 times, at the cost of top speed. Most transfer cases use a reduction somewhere in this range, however there are cases out there, built exclusivly for off road applications that have reductions of 4 to 1 or greater. the lower the reduction, the slower you go (which is great for rock crawling) and the more torque or pulling power you have. Again, in 4low both axles receive equal shares of the power until one begins to slip.

To accomplish 4wd, the t-case has two shafts, the main shaft and the front shaft. The main shaft spins all the time, regardless of what range or mode you're in. This is what drives the rear axle in 2wd and in 4wd. When 4hi is engaged, the shift fork moved by the selection lever locks in a gear to the main shaft. That gear drives a chain which then turns the front output shaft, causing the front drive shaft to turn the gears and shafts on the front axle. Note that because both axles are coupled by the chain, both will spin at the same rate. This is why it's not good to drive in 4wd unless there's snow or ice on the road. If one wheel tries to turn faster then the other, like in a turn for example, the slower wheel will have to spin to catch up, or else the chain will stretch or bind. On slushy roads or in the dirt or mud off road, the wheel will slip enough that this won't cause much of a problem, but dry pavement is a different story. In 4low, the driving gear that turns the main shaft is changed so that it now drives a planetary gear which in turn drives the main shaft. the planetary provides the large reduction in much less space then a similar reduction done with standard gears.

So now you know how to get both drive shafts turning but there's still one other component Chrysler decided to throw in (in all their great wisdom ) and that's the infamous front axle disconnect. All it is, is a shift fork that slides a coupling collar onto both ends of the two piece axle shaft on the passenger side of the axles. The way an open diff works, is that it will transfer power to the wheel that has the least amount of resistance. the two piece shaft on the one side of the axle means that, if the fork doesn't couple them, then the diff will see that side as having the least amount of resistance (slipping) and thus will send all the power there. This is why so many YJ owners have problems with their 4wd. the fork fails to move, thus the collar doesn't connect the shaft pieces together and you have a front axle that doesn't spin in 4wd. The reason the fork fails to move is because of the vacuum motor that moves it. or more often then not, the vacuum lines that feed said motor. When you shift the t-case into 4wd you also activate teh vacuum switch on the case itself, which sends a vacuum to the driver side of the shift motor diaphram. The other side of the diaphram is opened to atmospheric pressure, and the resulting pressure difference does the rest, pushing the diaphram and the shaft that it's attached to over to the driver side. The shaft is connected to the shift fork which moves the collar and viola, you axle is locked in. from your axle, vacuum pressure is sent to a simple vac switch mounted on the firewall which then turns the 4wd indicator light on in the dash. When you shift back to 2wd, the vac pressure is reversed so that the passenger side of the diaphram is now under vacuum, and the driver side is opened to the ambient air. This pushes the fork back to it's normal position and disengages the front axle. if at any point, one of the vacuum lines frays or cracks, creating a leak (air rushes in because of the vacuum inside the line, thus reducing the overall pressure difference or eliminating it entirely) then the whole system will not work. The shift motor itself (that diaphram I mentioned) can leak as well. Or the vacuum switch on the t-case can go bad. Any of these will render your 4wd inoperative becuase the axle shafts won't be connected. Apparently this is all done to reduce wear and tear on your differential and t-case (if your shafts were locked all the time, your front drive shaft and diff would constantly be spinning even in 2hi, thus reducing gas milage and increasing wear) however the TJ's all use a one piece shaft on the front axle as do many other 4wd vehicles on the road, so apparently it wasn't worth the headaches it caused

You may have noticed that the open diffs can cause you to lose total traction on either axle or both (Canuk pointed that out too) so really you only get a true 2wd system, even in 4wd unless you have lockers in one or both axles. The lockers do just that, they lock both wheels together causing them to spin at the same rate all the time (newer technology is allowing them to spin at different rates during turning but for the most part they spin the same all the time). In this case, if one wheel is spinning, you still have the other side of the axle spinning as well. With one axle locked you have a true 3wd system (2 spinning all the time with one axle varying between the two wheels) and with both axles locked you have a TURE 4wd system with all wheels constantly turning together. Limited slip differentials do something in between, allowing the power to be supplied to either wheel in varying degrees. Say 80 to the spinning wheel but still about 20% to the non spinning. At some point though, it's still possible to lose traction on one wheel of the axle due to the other spinning. It's also possible sometimes to fool the limited slips and the open differentials into thinking the spinning wheel has traction again by gently applying the brakes. the added resistance of the brakes will force the diff to start sending power back to the side of the axle that is stationary. This trick is best used when you're only a little stuck, like in a patch of slick mud that isn't deep, just slippery.

That's basically all there is to it. Any questions class? HTH
__________________
RIP: '88 YJ 2.5L Ax-5 NP231
Posi-Loked. Herculined. Optima yellow top. 1" Shackle, 2" BDS. Cragar 397's Aussie front.

92 YJ 4.0L Ax-15 231
5" springs, 1" shackle 31's or 35's depending on my mood
sentinal02 is offline   Reply With Quote
Unread 06-11-2004, 07:12 AM   #5
mikeyc
Registered User
 
Join Date: Jun 2003
Posts: 58
Wow, no...I'd say that pretty much covers it. Sounds like if I'm ever going to do any "serious" off roading I need to get at least rear lockers. I'm guessing that if I search around here I'll find all the info I ever needed (and some I probably don't need) on lockers and who prefers what set ups.

Thanks.

MikeyC>
__________________
94 Sahara
Stocky McStock Stock
Looking to do some work to it once I get out of school and have some money...
mikeyc is offline   Reply With Quote
Unread 06-11-2004, 01:05 PM   #6
sentinal02
H2 Recovery Team Member
 
sentinal02's Avatar
1992 YJ Wrangler 
 
Join Date: Feb 2003
Location: New York
Posts: 6,688
Quote:
Originally Posted by mikeyc
Wow, no...I'd say that pretty much covers it. Sounds like if I'm ever going to do any "serious" off roading I need to get at least rear lockers. I'm guessing that if I search around here I'll find all the info I ever needed (and some I probably don't need) on lockers and who prefers what set ups.

Thanks.

MikeyC>
yes, serious off roading is best done with at least one axle locked. however they get you in deeper and if you get stuck there then you'll need another rig that has a locker too to get you out. winch on the other hand will get you through some tough spots (can be a hassle if you're constantly having to winch through so pick your poison carefully) but it will usually get you out of things even a locker can't. Ideally you have both, but to me a winch makes more sense to get before the locker. then you don't have to worry about being stuck. if you wheel with guys that have a winch in the group (never wheel alone!) then I might say get the lockers first. I've heard the arguments for both sides and a lot depends on what you're wheeling and how your rig is setup but for me the winch comes first.
__________________
RIP: '88 YJ 2.5L Ax-5 NP231
Posi-Loked. Herculined. Optima yellow top. 1" Shackle, 2" BDS. Cragar 397's Aussie front.

92 YJ 4.0L Ax-15 231
5" springs, 1" shackle 31's or 35's depending on my mood
sentinal02 is offline   Reply With Quote
Unread 06-11-2004, 01:44 PM   #7
max3k
Registered User
1997 TJ Wrangler 
 
Join Date: Apr 2004
Location: Charlotte, NC
Posts: 291
jeep chick comes first for me...

NEVER WHEEL WITHOUT YOUR JEEP CHICK!
__________________
'88 YJ 4.2 5sp - Black w/ Black Sailcloth Top.
RE 4" Lift
Cragar 352's 15x8 on Goodyear MT/Rs 33x12.50
Bushwacker cutout pocket flares
PORC Rock Sliders
Big Daddy Front and Rear Bumper/TC
JKS Quicker Discos
Tom Woods CV Driveshaft w SYE
Yukon HD 456 gears
XM Radio
Cobra 75 WX ST
48" Highlift

Lifted, Locked, and ready to Wheel!!

Hello,

My name is max3k and im a jeepaholic
max3k is offline   Reply With Quote
Unread 06-11-2004, 03:24 PM   #8
mikeyc
Registered User
 
Join Date: Jun 2003
Posts: 58
hmm...that is a hard decision, winch, chick, or lockers...Didn't think this was going to be that difficult. Luckily I just started my first job and have no money, so guess I can postpone this decision for at least a couple months. Seems like tires at some point may be a good thing to add, and then of course there will be the matter of a good lift, and maybe some rock guards, and a rear bumper with hitch, and a soft top....AH CRAP I knew that the price I paid for my jeep wasn't going to be THE PRICE I paid for my jeep. Oh, well. At least it'll be fun thinking about and planning How does that saying go..Just Empty Every Pocket.
__________________
94 Sahara
Stocky McStock Stock
Looking to do some work to it once I get out of school and have some money...
mikeyc is offline   Reply With Quote
Unread 06-11-2004, 03:46 PM   #9
sentinal02
H2 Recovery Team Member
 
sentinal02's Avatar
1992 YJ Wrangler 
 
Join Date: Feb 2003
Location: New York
Posts: 6,688
and just remember, jeep chicks can empty your pockets even faster then your jeep.
__________________
RIP: '88 YJ 2.5L Ax-5 NP231
Posi-Loked. Herculined. Optima yellow top. 1" Shackle, 2" BDS. Cragar 397's Aussie front.

92 YJ 4.0L Ax-15 231
5" springs, 1" shackle 31's or 35's depending on my mood
sentinal02 is offline   Reply With Quote
Unread 07-04-2005, 12:04 PM   #10
fastone110
Registered User
1988 YJ Wrangler 
 
Join Date: Mar 2005
Location: chrisman,IL
Posts: 397
Quote:
Originally Posted by sentinal02
and just remember, jeep chicks can empty your pockets even faster then your jeep.
sentinals my hero
__________________
'88 yj wrangler 2.5L /w 3.5 black diamond suspension lift, 2" body lift, 1 1/4" shackles, detroit gearless front locker, lockright in rear, posi-lok, traction bars off, no sway, 35x12.50x15 baja claws on homemade beadlocks, 4.10 gears protected by homemade diff covers, TFI, herculined, 8000lb winch, GenRight Bumbers, BrownDog 1''MML, JB SYE, flowmaster, custom YJ dash, kicker 4" front speakers, sony explode cd player, rocker panel guards, custom SS red brake lines.
fastone110 is offline   Reply With Quote
Unread 07-17-2005, 08:50 AM   #11
bakwoodj2
Registered User
 
Join Date: Jul 2004
Location: Baton Rouge, LA
Posts: 118
Tires make a Difference too

Lockers will get you thru some tough spots. But i saw a Jeep with 32" BFG Mud Terrains and 3.07 gears do some things that others with me said needed lockers. So Tires help.
__________________
2004 Yellow Sport Named Cochise. KC daylighters on the windshield, 30" tires, 3.73 Gears and 2" RE BB. Cochise is gone. He got traded for a family "SUV"

1995 Green YJ Named LETSEE 2.5 liter, 2" BL, 32 x 11.5" Mud Kings on 15 x 8 Cragar Nomad rims w/4" backspacing, 5 forward gears now, T-fer case back together correct this time)!


There will always be a trail or obstacle that stops you, but that doesn't mean you have to like it!
bakwoodj2 is offline   Reply With Quote
Unread 07-17-2005, 10:03 AM   #12
yesterdaylight
Registered User
1995 YJ Wrangler 
 
Join Date: Jul 2005
Location: Troy, NY
Posts: 597
so a wrangler has front and rear open diffs even in 4wd, but does it also have a center differential ? if so is it open even in 4wd? i dont see why the tires would chirp turning in 4wd if the front and rears are open...
yesterdaylight is offline   Reply With Quote
Unread 07-17-2005, 12:03 PM   #13
sentinal02
H2 Recovery Team Member
 
sentinal02's Avatar
1992 YJ Wrangler 
 
Join Date: Feb 2003
Location: New York
Posts: 6,688
Quote:
Originally Posted by yesterdaylight
so a wrangler has front and rear open diffs even in 4wd, but does it also have a center differential ? if so is it open even in 4wd? i dont see why the tires would chirp turning in 4wd if the front and rears are open...
no, the TJ and the YJ use chain drive t-cases which couple the front and rear axles together. this is why using 4wd on pavement is asking for trouble. during turns the tires under power want to turn two different speeds and one of the tires has to slip in order for that to happen.
__________________
RIP: '88 YJ 2.5L Ax-5 NP231
Posi-Loked. Herculined. Optima yellow top. 1" Shackle, 2" BDS. Cragar 397's Aussie front.

92 YJ 4.0L Ax-15 231
5" springs, 1" shackle 31's or 35's depending on my mood
sentinal02 is offline   Reply With Quote
Unread 07-17-2005, 12:31 PM   #14
yesterdaylight
Registered User
1995 YJ Wrangler 
 
Join Date: Jul 2005
Location: Troy, NY
Posts: 597
Quote:
Originally Posted by sentinal02
no, the TJ and the YJ use chain drive t-cases which couple the front and rear axles together. this is why using 4wd on pavement is asking for trouble. during turns the tires under power want to turn two different speeds and one of the tires has to slip in order for that to happen.
oh i see because the front wheels have to travel around faster than the back wheels because they have a larger distance to travel. it all makes sense now . it disappoints me though that the 4wd system is completely open front and rear in a stock yj or tj. rubicon has optional lockers right? would it be okay to permanently lock a front diff on a wrangler because of the split axle? or would one be better off with manual lockers? i would think a stock wrangler could get around great with full time 4wd, ie.. everything locked. even without much of a tire upgrade and lift. does that sound possible?
yesterdaylight is offline   Reply With Quote
Reply
Thread Tools


Suggested Threads





Jeep, Wrangler, Cherokee, Grand Cherokee, and other models are copyrighted and trademarked to Jeep/Chrysler Corporation. JeepForum.com is not in any way associated with Jeep or the Chrysler Corp.