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Alan Yim (Alan)
| | Posted on Saturday, January 25, 2003 - 06:24 pm: | 
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Hey folks,
Can someone explain how the Jeep 4WD system works? I was heading home today and a guy in a JGC (fairly new - guessing within 6 months) was in the ditch on a hill (he admited he was driving too fast and lost control). I pulled over and waited to see if he could drive out but after a few minutes, it looked like he was in a bit of trouble. When I went over and talked to the fellow it was pretty apparent that he had no idea what he was doing. I asked him to put it into low range and lock his diff but he didn't know what I was talking about or how to do that so his wife suggested I drive. When I got in, the transfer case was in "Full-time Quadra Trac" and the only other options I had was "2WD", "part-time 4WD" and "4-Lo" so I put it into 4-Lo (no CDL so assumed it was electronically controlled) and got his truck about 3/4 way up the hill (not overly steep but long) before it got stuck. The snow depth in this ditch was to the bottom of his doors and in some spots almost to his bumper. My buddy was outside helping but he said that all 4 wheels never turned at the same time. Sometimes one side would go then the next side but never all four. I would have towed him out but that wasn't an option. This truck had no tow points anywhere, front or back (no hitch receiver either). He also had radial tires too so not much help there. Eventually a tow truck came and hauled him out but my question is do these JGC operate on fully electronic 4WD systems similar to ETC?
Was there something else I could have done? I actually came around from a different direction backed in through the ditch to where he was, in anticpation of hauling him out and that's when I noticed he had no tow points but I got in and out pretty easily so just wondering if it was a matter if incorrect driving with his vehicle or a combination of poor tires and a 4WD system not meant for that kind of situation. |
muskyman
| | Posted on Saturday, January 25, 2003 - 06:31 pm: |
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open front dana35 rear D44 with a real weak LSD
both partime4wd and 4 low lock the center dif
sounds like shitty tires was playing a roll in this,. a couple clicks of the parking break may have helped but not like it would have changed things nite and day or something.
the complete lack of extraction points is pretty much a sign of what jeep is thinking on this truck |
Alan Yim (Alan)
| | Posted on Saturday, January 25, 2003 - 06:37 pm: |
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Ya I was really surprised when I saw no recovery points. I'm standing there trying to figure out what I could do differently but in the end decided I didn't want to risk damaging his truck so left it to the tow truck company to deal with. |
Carter Simcoe (Carter)
| | Posted on Saturday, January 25, 2003 - 07:09 pm: |
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If your disco has the stock diffs then all 4 of your wheels won't spin at once when you are stuck either, that is normal and what lockers are for. The JGC guy probably had some of those annoying auto locking hubs where you have to actually drive forward for a little bit before they activate and effectively engage 4wd. |
mantaray (Mantaray)
| | Posted on Saturday, January 25, 2003 - 07:31 pm: |
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Jeeps have vaccuum actuated hubs, so the wheel has to make a 1/4 turn before 4WD is engaged. like musky said, open diffs front and rear. did you look in the openings of the plastic facia for an extraction point? they can hide them pretty well. the WJ (i'm assuming it was the newer style GC) is a very capable truck in the right hands, but having street radials definitely didn't help this guy much. |
Alan Yim (Alan)
| | Posted on Saturday, January 25, 2003 - 09:20 pm: |
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I practically crawled underneath his truck looking for extraction points but there was nothing. The front of his truck had plastic air dam that came down but his radiator actually could be seen behind it and the two spots that were open where extraction points could be were actually empty. They looked more like holes for fog lights than a place for extraction points. I saw a couple of JGC later and noticed one had a tow hook on the front but the other didn't so it looks like it's an option the user has to specify.
After I put his truck into 4-Lo, I actually drove it a good 50 yards before I couldn't go any further so if it did have auto locking hubs like Carter describes, they had plenty of opportunities to lock. But those tires were definitely not helping that truck very much. |
good ol boy
| | Posted on Saturday, January 25, 2003 - 10:00 pm: |
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GIVE IT HEEELLLLLLLLLLLLLLLLLLLLL |
Zinhead
| | Posted on Monday, January 27, 2003 - 10:45 pm: |
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In order to get extraction points on a JGC, it is necessary to get the "up country" suspension which also adds skip pads, more agresive tires and a small lift. The more expensive JGC also have a different, permanent 4WD system with viscous coupling in the middle and limited slips at boths ends. It can be a very capable truck although in base form it isn't. |
muskyman
| | Posted on Monday, January 27, 2003 - 11:00 pm: |
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if you read the original post this one deffinetly has the non VS TC |
Peter Carey (Pcarey)
| | Posted on Tuesday, January 28, 2003 - 06:23 pm: |
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The tow hooks can be put on after market or ordered with. The kit is about $100 and includes brackets to extend inbetween that cheap plastic grill thing.
It was one of the first things I had put on when I got mine since I knew I would get stuck or have to pull someone sooner or later.
pwc |
Peter Matusov (Pmatusov)
| | Posted on Tuesday, January 28, 2003 - 06:53 pm: |
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Quote:Jeeps have vaccuum actuated hubs
is it about jeeps in general? or Grand Cherokee?
IIRC, jeeps never had vacuum actuated hubs. Neither it had to do anything with a wheel having to make a 1/4 turn for the hub to engage.
the Quadratrac (whatever it ever stood for) only means differentiated (full time) case with limited slip mechanism built into it. In jeeps, it has never been very tight (unlike range rovers), but the Quadradrive version has progressively locking center and axle diffs.
Engaging "Part-time 4Hi" would have locked the center diff, just what you had to do. Low range may not be of any help if the traction was marginal.
two more comments here -
- i don't know how one can possibly tell whether or not all four wheels turned at the same time;
- if the JGC made it 3/4 out of the ditch with the snow up to its bumper, it ain't so bad at all.
peter |
Alan Yim (Alan)
| | Posted on Tuesday, January 28, 2003 - 08:32 pm: |
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The fellow standing outside the vehicle helping me said that he saw the wheels on one side (ie. driverside) spin, then the wheels on the opposite side spin but it didn't look like it was finding traction. This could have been largely due to poor tires. When I was driving the vehicle, it didn't feel like it was gripping very well/at all. As for making it up 3/4, I was surprised as well but there wasn't much I could do. The tires weren't gripping very well so I wasn't able to actually guide it in any particular direction. The only direction I could move the vehicle in, was straight and that took several attempts before I could get it going. |
Peter Matusov (Pmatusov)
| | Posted on Tuesday, January 28, 2003 - 08:36 pm: |
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huh Alan,
i didn't realize it was you - so the question about the snow being wet kinda falls off on its own 
i believe it's not the 4WD setup that kills the JGC, it is the really piss-poor ground clearance (just look at that abomination of a gas tank), and shitty tires. The WJ JGC is worse than ZJ JGC in that matter, which is sad 'cause QT and QD are not bad set-ups at all.
peter |
Alan Yim (Alan)
| | Posted on Tuesday, January 28, 2003 - 10:43 pm: |
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Ya it was me helping this fellow. He didn't know what he was doing and I happened to drive by so I offered to help. The snow was crystally but deep (in some spots where I was walking through, the snow was past me knees) and it was quite cold so no wet snow to affect anything but ya the JGC was quite low. Even though the snow was powdery, it wasn't falling off the tires but packing into the tread quite tightly and effectively making them slick.
I didn't really think it would be the 4WD system as I've gone wheeling with other Jeeps and they had no problems but thought I'd ask anyway as it just seemed that I got in and out rather easily but my friend who was watching did say my truck had/has more clearance than he did so it wasn't really that big a factor for me. I'm also running BFG AT's too so big difference in grip.
I think this JGC was a Laredo model as it had the plastic grey bumpers and no fogs but I can't say for sure. I didn't pay a lot of attention when I was poking around underneath for extraction points.
In the end the guy was towed out by a tow truck so he was fine. |
Leslie N. Bright (Leslie)
| | Posted on Wednesday, January 29, 2003 - 08:15 am: |
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Peter,
I don't know about the WJ/ZJ, but on the Command-trac XJ I had, when you pull the x-case lever into 4wd, there's a vacuum-actuated collar that slides along the front axle... at the same time, the autolocking front hubs would engage. The collar triggered the hubs' lcoking, and the wheels had to roll forward to finish locking.... you couldn't engage it while sitting still. When disengaging 4wd to return to 2wd, you had to back the vehicle up several feet to to get the auto-locking hubs to disengage...
That was a big problem on the XJ I had... the collar would bind up... you had to remove the access cover and hammer the collar 'til it popped loose, then the 4wd would engage.... that was a PITA....
-L |
muskyman
| | Posted on Wednesday, January 29, 2003 - 10:11 am: |
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yep same thing on all hubless D35 front axles
i have put a couple cable actuaters on them, fixes the problem/design flaw but you still need to roll a 1/4 turn to get lock.
shouldent need to back up ,first corner that turns the diff should unlock the hubs
key word "should" |
Peter Matusov (Pmatusov)
| | Posted on Wednesday, January 29, 2003 - 12:06 pm: |
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Leslie and Thom,
note that hubs are not actuated by the vacuum.
i know about the ugly-ass front D30 and even D44 (on the Grand Wags) with a vacuum disconnect, but it was an axleshaft that got split or connected.
peter |
Renegade
| | Posted on Tuesday, February 04, 2003 - 11:20 pm: |
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JGC, also know as ZJ's or the newest model being the WJ have a D30 front(not 35, those are only rear axles) and a D44AL (aluminum) rear. The rear has a crappy Trac-Lock LSD. The T-case is a NP241. The Dana30 front axle is Vacume activated on all Jeeps 1987-up...It is a awfull system typicly coverted to a 4X4Posi-Loc cable system.
(Yes I am a Jeep guy but Im in the middle of building my Discovery...setting it up on 35" Baja Claws) |
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