My jeep has the QTII transfer case, which as most of you already know, means it applies power to front/rear as needed based on wheel slip. My question is this: What is the time it takes to engage the front wheels once the rears start slipping? Is it instantaneous, or does it take a bit? Also, how long does the front axle stay engaged once power has been transferred to the front?
Look at
However when in a really tight turn:
"But the problem is not this 0.5s, the problem is that single second of fear, in which one does not know how the Grand will finally react. At first one drives a VW bug, a rear-skidder, and the next moment a true 4x4 vehicle. Which of the two must one be prepared for?
Larry Greenwood
Applies the brake? As in actually compresses the brake pad against the rotor on the wheel that is slipping? This doesn't sound right. If that were the case, that would mean the computer would have to control the 4x4 somehow, and based on the link you provided, it mentions the system is mechanical, not electrical. (of course the link discusses the QuadraDrive system, not the QTII system. but from what I understand the only difference is the addition of a vari-lock diff in the axles.)
Seems strange if a wheel starts spinning in the mud, the brake would be applied to transfer power. Sounds similar to driving down the road while depressing the brake pedal at the same time. ??
Can anyone else confirm or deny the explanation by Bill?
Sorry, but the previous post is wrong - the brake is never applied on the QTII.
The link that L.W. provided does a great job of explaining how the system works - it's 100% mechanical, essentially combining the concepts of how an oil pump works and how a clutch slave cylinder works.
As to your question, I would agree with the 1/2 second statement.
Bottom line, it's an awesome 4WD system.
About two years ago, I was launching my SeaDoo off of a boat ramp with my
2WD Dodge Truck. The water level of the lake was low so I had to back far down the ramp to launch the SeaDoo.When I retrieved my SeaDoo I backed the Dodge past the end of the concrete boat ramp onto the soft gravel. It was almost buried to the axle before I gave up.
I drove my '99 GC down the launch and pulled forward until the two vehicles were almost "nose to nose."
I then secured a 10,000 pound tow strap to the frame of the Dodge and wound the strap through the front tow hooks on the GC.
When I started to back the Jeep up the ramp, I could feel the rear tires bite the concrete ramp for traction. After only minimal wheel slip I could feel the front suspension compress as the front wheels clawed for traction. Before the Dodge "popped" out of the hole that I dug, the Jeep managed to use each of the four wheels to claw for traction on dry concrete - at one point, all four wheels were turning at the same time.
Sorry for the long post, but I didn't want you to mis-understand how the system works. If you are still unclear, I would recommend the link in L.W.'s original post.
As a side note, the Mercedes 4WD system on the ML SUV works exactly as L.W. describes.
Have a great week and enjoy your new Jeep.
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The Jeep rep explained it to me as 1/8 of a turn of the slipping wheel. He said that once a year factory guys come to town and do a 'Jeep 101' class for new owners and one of the demo's is to jack one of the GC's off the ground and let people see it in operation. I have not been to one of these demo's but maybe someone else has been to one and can let us know what they saw.
Bill,
But that is a Chrys. 300M, not a Jeep Grand Cherokee. (not exactly apples to apples, ya know?)
Thanks for clearing that up Scott, something wasn't sounding right with that post.
Bill, I don't think I have the vari-lock, that would mean it is the Quadra-DRIVE
4x4 system, correct? I have the Quadra-TRACII, same xfer case at DRIVE but without limited slip diffs. (i think??) At any rate, it looks like this issue has been cleared up above. If nothing else, I've learned to take what you read in newsgroups with a grain of salt...... ;)"L.W. (ßill) Hughes III" wrote
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