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Savvy/Currie Aluminum Control ArmsRockridge 4WD IS Taking Zone Offroad Suspension Lift Kits ZONE 4.25" combo lift for TJ available at Rockridge4w

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Unread 09-01-2012, 11:59 PM   #31
05Unlimited
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Oooohhhh .............I have an age old question that I'll bet you can answer! Literally about 21 years ago I remember something happening that I still to this day do not understand. When I was in college we lived close to this "good ol' boy" who sometimes did some backyard mechanic stuff. I had a 1979 Buick Regal with a 301 4V and 200 Metric Trans (obviously it had an open diff rear end...yes ..for sure ...2.73's and all). I was in his yard one time trying to drive it up onto some ramps and couldn't get enough traction in the gravel lot to make it up. He said "put it in 1st gear ...it puts more torque to the rear end". Knowing that it was an automatic and started out in 1st gear by default anyway, I was puzzled by his instruction. None the less, I pulled the old 3 speed automatic lever down into "1" and feathered the throttle ....the car climbed right up the ramp! To this day I have never understood this ...but always forgot to pursue "why????". So now I finally remember to ask in an appropriate venue. So ....why on Earth did my old 3 speed automatic have a posi-effect on an open differential when the trans lever was placed into "L1".??????????? I'm telling you ...this was not my imagination ...it was a NIGHT AND DAY effect!!!!

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Unread 09-02-2012, 04:43 PM   #32
rockspyder
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Can't wait to hear an answer to this one!
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Unread 09-03-2012, 11:53 AM   #33
Jerry Bransford
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Quote:
Originally Posted by 05Unlimited View Post
Oooohhhh .............I have an age old question that I'll bet you can answer! Literally about 21 years ago I remember something happening that I still to this day do not understand. When I was in college we lived close to this "good ol' boy" who sometimes did some backyard mechanic stuff. I had a 1979 Buick Regal with a 301 4V and 200 Metric Trans (obviously it had an open diff rear end...yes ..for sure ...2.73's and all). I was in his yard one time trying to drive it up onto some ramps and couldn't get enough traction in the gravel lot to make it up. He said "put it in 1st gear ...it puts more torque to the rear end". Knowing that it was an automatic and started out in 1st gear by default anyway, I was puzzled by his instruction. None the less, I pulled the old 3 speed automatic lever down into "1" and feathered the throttle ....the car climbed right up the ramp! To this day I have never understood this ...but always forgot to pursue "why????". So now I finally remember to ask in an appropriate venue. So ....why on Earth did my old 3 speed automatic have a posi-effect on an open differential when the trans lever was placed into "L1".??????????? I'm telling you ...this was not my imagination ...it was a NIGHT AND DAY effect!!!!
Shifting into Low had no effect on the axle or its ability to not spin. You might have been more careful with your application of the gas at the time after shifting into Low, that is the only possible reason.
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Unread 09-05-2012, 08:07 AM   #34
05Unlimited
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Originally Posted by Jerry Bransford View Post
Shifting into Low had no effect on the axle or its ability to not spin. You might have been more careful with your application of the gas at the time after shifting into Low, that is the only possible reason.
Makes perfect sense to me, although I was there at the time and witnessed an unbelievable difference in traction. I wasn't trying to apply the gas any more carefully ...it was a night and day difference and it has always bewildered me. Maybe the good old boy knows something we don't just from repeated experience if nothing else. To me it makes no sense at all. Maybe it was a freak thing but I'll never forget how differently it dug into the gravel after being shifted into L1 (like it had no chance whatsoever in D but when shifted to L1 it just went right up the ramp effortlessly). I had said ..."yeah right, like shifting into L1's going to make any difference" ...then I tried it and was like "WTF?!!?!?!?"
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Unread 09-12-2012, 01:11 PM   #35
harleysilo
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As i was reading through this thread i was remembering a feature on my dad's tractor I used to use a lot, left and right brake controls for the rear wheels. Then i started wondering, if i had individual control in applying the emergency brake to the left or right rear tire, then I could almost have a locked rear axle (assuming i understood all of what i read). Not that it would be very practical to keep applying/removing the braking to each rear tire when needed on a long run, but if it was just a once in awhile thing on a run it might be nice to have...of course someone would have to make the new 2 in one brake handle.
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Unread 12-08-2012, 03:28 AM   #36
jnicewan
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Originally Posted by harleysilo View Post
As i was reading through this thread i was remembering a feature on my dad's tractor I used to use a lot, left and right brake controls for the rear wheels. Then i started wondering, if i had individual control in applying the emergency brake to the left or right rear tire, then I could almost have a locked rear axle (assuming i understood all of what i read). Not that it would be very practical to keep applying/removing the braking to each rear tire when needed on a long run, but if it was just a once in awhile thing on a run it might be nice to have...of course someone would have to make the new 2 in one brake handle.
Modern vehicles including some Jeeps do this through the ABS for traction control, stability control etc. Some vehicles can get pretty complicated actually. Some AWD systems use a clutch in the t-case that can transfer power to the frt or rear, then they can apply braking effect to individual wheels to control wheel spin and some even reduce engine power to control wheel spin.

2 in 1 brake handles are out there already and a lot of their uses are in sand rails/buggys for turning brakes. One type uses a simple handle when you pull up it engages one side, push down it will engage the other, others might have 1 handle for each brake, then you also have a regular brake pedal for both. Some crawlers get 2 center hump mounted park brake pull levers and hook them up to the individual rear parking brake cables on rear, they are manily used for turning brakes too and you can pull the locking button off for quick grabbing and releasing.
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Unread 12-14-2012, 01:38 AM   #37
billzcat1
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Quote:
Originally Posted by Jerry Bransford View Post
Shifting into Low had no effect on the axle or its ability to not spin. You might have been more careful with your application of the gas at the time after shifting into Low, that is the only possible reason.
I think I figured out this mystery.

The torque converter is a torque-multiplier until it reaches its stall speed. He was spinning tire because while trying to climb the ramps in "D" it was below the stall speed and applying too much torque.

Shifting it down into "1" didn't provide more torque or more traction. The solution that allowed it to climb the ramp was actually less torque applied to the wheels.

I'm thinking there was some sort of solenoid or somesuch that allowed the torque converter to lock up sooner (much like how O/D off in our Jeeps disengages the TC lockout). So in effect, he was getting the converter to a lower stall point and therefore NOT magnifying applied torque to the axle.

At least that's a possible mechanical answer for what happened. Whether said solenoid or low-stall converter exists is beyond me. Just pulling an idea out of my *** that could possibly explain the situation.
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Unread 08-19-2013, 07:18 AM   #38
B_faster
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Originally Posted by billzcat1 View Post
I have to address this because this question hasn't been answered correctly, and the replies show some misunderstanding about the QuadraDrive system.

The QuadraDrive system found on WJ Grand Cherokees uses a gerotor-driven hydraulically-actuated progressive clutch pack in the transfer case as well as in both front and rear differentials. When there is a speed differential front/rear or side/side, the gerotor develops hydraulic pressure which then compresses the clutch packs and progressively locks the axle (or transfer case). There is a bleed port with a spring that tunes the amount of pressure generated - without it, the axle would engage the clutch pack during every turn. With that bleed port, it allows enough slip to negotiate corners without binding but still provide nearly-full-lock up when significant enough wheel spin is detected.

There is nothing electronic about it, no traction control, no ABS actuation involved. It doesn't detect slip and then clamp that brake caliper to stop it or "redneck locker" when it slips. It's also a lot more durable than the older Traclok differentials since the clutches are not engaged during 99% of all driving.

The WK Grand Cherokees have a similar system but the differentials have a small revision to the bleed port. Instead of a spring, it is now an electronically-controlled aperture so lock-up can occur more quickly when needed. However, you are at the mercy of electronics - while more tunable there is also a delay while the system decides what to do and also you have the potential for damage to the wiring while on-trail.
Richard,
As a new to me 99 WJ with quadratrac, thanks for the explanation. I have been out of the Jeep world for a few years, been missing my 06 TJ Rubi Unlimited, I am now back. The WJ fits the niche for people hauler/RV toad/light recreational vehicle.

Darin
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Unread 11-29-2013, 01:31 AM   #39
JohnnyZero
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The idea that the engine is not creating torque without resistance is incorrect. It is true that it does take a source of resistance to be able to measure
that torque, but the torque coming from the engine is the same whether resistance is present or not. The differential does not split the power 50/50 but rather
sends the power through the path of least resistance. If you have one wheel off the ground and the other on the ground the one off the ground will be receiving
all of the power. With all do respect as I am new here and I can see that this was posted by a moderator, there is a lot of misinformation in the original post.
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Unread 11-29-2013, 09:25 AM   #40
billzcat1
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I understand where you are coming - it makes "logical" sense that the engine is still making the torque. BUT it does not mathematically balance to have all this engine torque being produced but not being used to accelerate something (be it the vehicle or even just the rotating assembly/driveline/wheel/tire during a burnout). That force (and as an extension) energy has to go somewhere. *SOME* of it gets put into accelerating the driveline, and *SOME* of it is used up in friction/heating of the spinning tire but this is a negligible amount compared to what the engine is capable of producing when there is a load. Have you ever looked at dyno sheets done in different gears? In theory, it shouldn't matter what gear you are in, the engine always "makes the same amount of torque" according to you. But you'll notice a drastic difference in power/torque output as you go across the gears (no, not as a result of gear reduction) but as a result of additional load added on the dyno. I watched the very same effect doing dyno pulls on a Dynapack where the load is regulated hydraulically and you can watch the engine make minimal power/torque at WOT with no resistance and then make its rated/expected power when the resistance is increased.

And you are flat out wrong on the function of an open differential. It ALWAYS splits torque 50/50. The wheel that is not spinning is providing the same accelerative force that the spinning wheel is - not very much. When you have one wheel off of the ground, that wheel spins and the other wheel provides the same accelerative force - zero. How is that not equal distribution?
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Unread 12-02-2013, 10:01 PM   #41
JohnnyZero
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I was wrong. My bad. Ha ha!
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