I hear some good things about their JGC QDII system, how it can lock all three differentials, send all power to just one wheel, etc. I was wondering if any experts here can compare and contrast both systems and objectively say which one is better?

The QDII is Jeeps top of the line 4wd system. I know two guys who have it on Jeep Grand Cherokees and I honestly dont think it performs any better than the 4wd system in our 4Runners.

Check out this link from the Jeep Commander forum where the QDII system is compared to a 4wd 4Runner:


http://www.jeepcommander.com/forums/...hlight=4runner

Even STeven, is that you posting over there??

The comparison between QDII and ATRAC is a tough one! From what i have read, it is better than the old QD system. Here are some links of the horrible QDI system:

http://md.co.za/jeep/
http://md.co.za/jeep/video.htm

QDII is supposedly more effective. However, there's a catch. Yes, IN THEORY, the ELSD/QDII can "pseudo-lock" an axle, thereby similating a locker. Why only in theory? Well, like QDI, there must be a way for it to unlock when you're making a turn or when there is too much stress on the differential. The only difference (my guess) between QDI and QDII is that QDII uses an electronic brain which integrates your steering and throttle to the QD system. QDI uses a bypass valve to release pressure when stress on the differential is too high (e.g. while turning or when one wheel is on ice and the other on high friction surface). QDII uses electronics to monitor when the wheels are turned or when to disengage due to excess stress.

Why is this bad? Well, if you're off-roading, then you do not want the system to think for you. You do not want to crawl up a rockledge and all of a sudden the electronic brain disengages your locker because your steering wheel is turned or that there is too much load on the rear diff. This was what was happening to the QDI system...too much load/stress and the system disengages it's clutch packs...which means, you're screwed.

Ahh, clutch packs. The problem with clutch packs in a differential or transfer case is the wear-and-tear. Clutch packs wear with use. Clutch packs require maintenance, such as changing differential fluid often. esp. if you use it often, thus leading to heat buildup which shortens the life of the fluid. Therefore, you do not see any experienced off-roader with clutch-pack LSD or lockers. What you do see are GEAR-based LSD (Torsen) or lockers (ARB, Rubicon's, G500).

So, in conclusion, although it can IN THEORY route 100% of power to any one wheel, it does not do it faithfully. And as QDI system showed, Jeep lies about their 4wd systems. The ONLY system that i do respect from Jeep is the one in the Rubicons. Thus, i do agree with that 4runner guy on the Commander forum...both systems are pretty much equivalent...both are equivalent to LSDs. Despite what Jeep claims, QDII is still a bunch of clutch-pack LSDs.

Hope this helps.

The guy's quadra-drive system on his "new" Jeep was obviously broken. It's clear from the dates of some of the posts that something did not make sense on his "new" Jeep, and the fact that he was complaining via the web is probably why most of us chose a Toyota in the first place. The other Jeep videos in the other post did not even appear to quadra-drive equipped. I am sure the record has been set in other posts, but quadra-drive when properly working is an incredible system whether QDI or QDII. Also, QDI was purely a mechanical viscous locking system so that information in the above post is confusing--- if the locking released it means your QDI is broken. I could not afford the v8 4 runner I wanted so I purchased a Jeep for a whole lot less, but I assure you I would have preferred the 4 runner. However, the QDI system does seem to outperform 4 runners with ATRAC especially in our mountainous areas from what I've seen but that could be more due to suspension, angles, etc. Check out this video which clearly shows how all 4 wheels eventually lock--albeit QDII
Toyota Land Cruiser Recovered by Jeep Grand Cherokee WH HEMI - YouTube