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My ’01 WJ is equipped with Quadradrive, by design it sounds like the best all around system for a 4-wheel drive vehicle. However, since I’m a bit ignorant about drive trains how about you folks give me the basics “101”.
 How does Limited Slip work and does my WJ use this in either the front or rear differential?
 I’m aware of Gerotors used in the Quadradrive and basically how they work, but do they work in conjunction with Limited Slip in place of?
 What Dana model diffs come on a WJ w/ Quadradrive & 4.7 V8?
 My most recent 4-wheelin’ trip (YO Ranch Jamboree) proved again the capability of WJ. I was continually surprised how well WJ w/ QD climbed, I was able to climb hills, slick rock, steps that I would have never guessed the vehicle could do. Most everyone would gather around and watch with amazement (the vehicle’s ability made the drive look good). However, I did experience wheel spin on a few occasions. Partly due to driver error and other time’s limitations of the QD systems. This would usually happen on very steep assents, I’m guessing it might have something to do with weight distribution. What should I expect from the QD drive train?
 That brings me to “lockers”, I’ve read a recent listing on the Tech Forum, but got confused rather quickly, information over-flow. Since the WJ will always be my daily driver is it wise to monkey around with differentials?
 One thing that will help is better traction. The WJ came with Goodyear SR-A (useless off road) when I replaced them last year my only option for 17” wheels was the Goodyear AT/S in a 265/70 R17. This has been a good tire however this last trip demonstrated their limitations. I’m thinking about a more aggressive tire, there’s a better selection these days the Goodyear MT/R seems like a good candidate, what do ya think?

Well enough already, don’t mean to ramble. Appreciate the advice and information.
 

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On 2002-03-12 07:53, DASJEEP wrote:
„h How does Limited Slip work and does my WJ use this in either the front or rear differential?
A Limited slip differential (LSD) works by torque and high friction "clutch" discs. Essentially, the torque applied to the differential through the drivetrain gets applied to the clutch discs which are connected to the axleshafts. The more torque, the more effectively the axle shafts will rotate together instead of having one spin freely while the other doesn't spin at all.

The quadradrive differential, is of course, not a LSD.



„h What Dana model diffs come on a WJ w/ Quadradrive & 4.7 V8?
I believe, but not sure, that you have a Dana Model 30 in front and a Dana Model 44a (the 's' stands for aluminum.)

„h ... What should I expect from the QD drive train?
Expect the world, but don't be disappointed when it doesn't happen. :) The nature of the gerotor is such that it requires some of the undesired characteristic (wheel spin) in order to get it to start operating. The mechanical nature of the diff is such that it will allow for different levels of that slip under different conditions

„h That brings me to ¡§lockers¡¨, I¡¦ve read a recent listing on the Tech Forum, but got confused rather quickly, information over-flow. Since the WJ will always be my daily driver is it wise to monkey around with differentials?
There are a number of manually operated positively locking differentials on the market today (ARB, OX, E...) By replacing your quadradrive diffs with any of these, you will only be enhancing the traction capabilities of the axle in question because you will have full traction at all times the locker is engaged - no room for any more wheel spin. Because they can be disengaged, they will not hinder on-street performance.

„h ... I¡¦m thinking about a more aggressive tire, there¡¦s a better selection these days the Goodyear MT/R seems like a good candidate, what do ya think?
The MT/R is an awesome tire - of course I'm biased (not radial.) :D

Jay
 

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Before considering installing any type of limited slip or locking traction devices in your differentials you want to confirm what you have in the back. If you have a V8 then have the Aluminum Dana 44. There are no after market traction enhancing devices available for this differential, and very unlikely there ever will be.
 

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The main "user experience" difference between the axle side gerator's of QuadraDrive and an LSD is in how they deliver torque to the non-slipping wheel. They both are designed to function on onset of wheel slip, HOWEVER the big difference is the torque transfer.

In an LSD application, the amount of torque supplied to the non-slipping wheel is limited by the total torque supplied to the axle. The non-slipping wheel gets 50% of the torque, the slipping wheel gets the other 50%. The goal of the clutch packs in the LSD is to load-up the slipping wheel so that more torque is supplied to the non-slipping wheel. For example, say under normal driving conditions the rear drive shaft can supply a maximum 100 lb.ft of torque (Tmax) to the rear axle. (this is just an example). The differential will evenly split the Tmax between the right and left wheels, so that each gets 50% of Tmax or 50ft.lbs. Now say you take your LSD equipped rear differential offroad. You get into a slippery situation. Wheel spin happens. The right rear starts to slip at 5ft.lbs. of torque. Thus in an open differential, now the left only gets 5ft.lbs. too. A total of 10ft.lbs. of torque is now being delivered to the rear axle. This is not enough to move your rig and you are stuck. With our LSD installed in the same situation. The right slips at 5ft.lbs. Now the clutch packs start to "engage" and load up the slipping wheel. The clutchs are in real good shape and will allow pretty good lock up. So they load up to about 20ft.lbs. Now the rear axle is getting 40ft.lbs. and this is enough to start to move the vehicle. As the vehicle starts to roll the clutchs become unloaded again (doesn't take much) the clutches will start to disengage, and cause wheel spin again, and the cycle repeats (load up/engage/roll/disengage --> repeat).

Note however, from above that with an open or a LSD differential the maximum torque supplied to the non-slipping (high traction) wheel is limited by the maximum amount of traction that can be supplied to the slipping (low traction wheel).

THIS IS NOT TRUE WITH QuadraDrive.
In QD, when the computer senses differentiation between right and left wheel rotation, it draws the conclusion that a wheel is slipping. The computer then directs the gerotor pump to incrementally engage. So in our mythical 100 ft.lb. rear axle example, if right rear begins to slip at say 5ft.lbs. the gerotor pumps will incrementally start to "engage" and start off with 5ft.lbs to the left rear. But this is not enough to move the rig, the computer senses this, and tells the gerotor to incrementally increase the torque delivered to the left wheel until the rig starts to roll. Ultimately the QD system can deliver all 100ft.lbs (Tmax) to one side, as opposed to only 50% of Tmax. (QD is more though, because the gerotor is present in the Transfer case too, and can actually direct 100% of the Torque available at the Transmission's output to any one of the 4 wheels under the WJ).

HTH
Zac
 

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Discussion Starter #5
Hey thanks, I'm digesting what's been posted.
JayH: Going to lockers say to the front diff would eliminate the function of the QD at that diff. Therefore, it would operate like an open diff when not engaged? And I guess the TC with a gerotor would still transfer torque to the front but to no use.
Zac: Is the QD system "active"? I thought the whole QD system was "passive", i.e. no electronics.
 

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Active/Passive - I do not know. It wouldn't really matter though. Whether a mechanical system detects the rotational wheel differential, or whether a computer controlled system does it (For instance the ABS controller), the result is the same.

Perhaps I took liberty with using the term "computer," and should merely limit the description to "detection of rotational differentiation in relation to vehicle speed and torque delivered." Not only is the progressive varilock system used by QD sensitive to vehicle speed (ie wont engage around corners on dry road, won't engage front end around corners on dry road, especially in tight turning situations) it is also sensitive to torque delivered (won't instantaneously deliver 100% of output torque to one wheel - as results would be disastrous - even though it can ultimately do so.)
 

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On 2002-03-12 10:26, DASJEEP wrote:
JayH: Going to lockers say to the front diff would eliminate the function of the QD at that diff. Therefore, it would operate like an open diff when not engaged? And I guess the TC with a gerotor would still transfer torque to the front but to no use.
For the types of lockers we're talking about, yes. When they're not engaged, they act as open differentials.

I'm not familiar with the 247(?) case. Does it have a 2WD option? If it has a 2WD option and you use that on the street then it will not deliver power to the front axle. If it only has 4wd options (full time/part time and lo for example,) torque will still be applied to the front axle and it will be used; The only differnce you'll experience with having an open diff is that as soon as one wheel loses traction, that wheel gets all the torque being sent to that axle from the case.

Jay
 

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I noticed the info on the QuadraDrive system. I have a 96 ZJ Ltd. 5.2L. It has the 249 T-case (quadra-trac), I have noticed that it does a good job of transfering power when you are already moving, however when starting from a sitting position, the story is different. I've noticed that when pulling someone out that is stuck, or try to pull a trailer, that if you apply gas slowly, only two wheels will pull, either both front or both back. The only way to get them all to pull is to go ahead and gun it after the first two are spinning, when they get up to about 15-20mph, the others lock in and she will pull. I know that lockers are the solution, but there are none made for my jeep b/c of the allum. in the diffs. Does anyone else have this problem and what is a good way to aviod this, one time my jeep just burried the rear end and the front never pulled: I was trying to pull a small boat out of the water on a sand ramp. Would putting the Jeep in 4-Lo before starting to pull be a good idea? I didn't know if that would help or if it would just burry me faster. Thanks for any info.
 

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The quadra trac is a completely different beast than the quadra drive - completely. Yes, 4 LO would have helped in your situation - the '96 and later q-tracs had a feature where the front and rear driveshafts were both always under power when in 4LO.

If you want to pursue this thread farther, please start a new topic. That way any and all who know about this and/or are interested in it, can get involved. Thanks.

Jay
 

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WJ...1999 or later...LOCKED in 4 LOW...
Wheelspin from wheel "A" causes the gyrator oil pump to pump pressure to cluches.. proportional to the wheel speed difference between wheel "A" and wheel "B"... The pump can only work(pump pressure to cluches) when there is a difference in wheel speed. For the "traction wheel" to continualy have traction, the "non-traction wheel" MUST continualy spin MUCH faster. Again..see grand photo page 55 Don S test. The WJ will only CLIMB 40 deg ramps with non-traction wheels spinning Perhaps 45 mph(this is not good in large loose rocks). :)%(.........Don S..
 
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