How does 4x4 really work

Last night got a bit stuck in a big snow bank, Selectrac I6 4x4, i was on full time

The rear right (passenger) wheels was spinning and it feel it was the only wheel really trying to get out, i know the 4x4 is working (Light on and feeling while doing u-turn ) but why i did not see the front wheel spinning while the gc was on Reverse , I was outside with the truck engage looking at the truck spinning. !!!!!

I tried part time and no much luck. Got out of there with time and patience REVERSE,DRIVE,REV... Is AWD subaru vehicules working the same ?

thanks

Pat

Reply to
Patrick
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please no reply like this LOL

1.. Find a passenger-helper. 2.. If you have manual hubs, lock 'em. 3.. Get into some real wet slippery mud. 4.. Engage 4 wheel drive. 5.. Stop the Jeep (in the mud). 6.. Turn the steering wheel all the way right. 7.. Stick your head out the driver's side window. 8.. Look directly at your front wheel. 9.. Floor the accelerator, only for a sceond or two. 10.. Pull your head back in and look at the passenger-helper. 11.. If the passenger-helper is laughing, your 4 wheel drive is likely engaging.

"Patrick" a écrit dans le message de news: i snipped-for-privacy@b2b2c.ca...

Reply to
Patrick

Next time try applying the parking brake a bit. This should help kick in the limited slip (left/right).

As far as the select trac (front/rear) I am not sure how those transfer cases work. I am imagine the parking brake might also help that too. My son never had a problem like that in his '94 Grand 5.2l, I am not sure if it is the same transfer case.

--James

Reply to
RocknCJ

Ok i see with the rear wheel not spinning free anymore the other wheel will lock. is that it ? Interesting i can't wait to have other reply.

Thanks

Pat "RocknCJ" a écrit dans le message de news:

7o3Ed.79359$QR1.76872@fed1read04...
Reply to
Patrick

Here's a brief writeup on a similarly common question I did sometime back, it may be helpful. Click on

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Jerry

Reply to
Jerry Bransford

Thanks that was helpfull.

pat

"Jerry Bransford" a écrit dans le message de news: r54Ed.23292$232.5389@fed1read05...

Reply to
Patrick

this is curious...'(quote the posted article)'...

"Finally, a full-time 4x4 system like comes on most Grand Cherokees and some Cherokees and Liberties 'couples' the front and rear axles together, but they are not mechanically locked together like a part-time 4wd system does. The coupling can be done via either a differential (just like what is between the left and right tires) or a fluid (viscous) coupler. The benefit to a full-time 4wd system is that because the front and rear axles are not mechanically locked together, the front and rear tires/axles can rotate at different rpms from each other. This allows a vehicle with a full-time 4wd system to drive in 4wd "full time" on a paved road without problem since there is no 'wind-up' problem to harm the drivetrain."...

I was driving in some fresh snow today, packed/loose mixed... and as usual, I used my "Full Time" 4WD, but I (unusually) was slipping a bit on a very steep hill and sharp corners and tried "Part Time" and it seemed to work better. So what gives? I thought "Full Time" was supposed to be better. (I would never use the "Part Time" on dry pavement)

Reply to
Richard

Part-time 4x4 is a more aggressive system that works better when the road conditions get really nasty. No matter what, a part-time system will make sure both your front and rear axles are turning. A full-time system will not always be able to do that due to how the transfer case doesn't truly lock the front and rear axles together... they are only loosely coupled together via a system that may let one end slip and spin while providing little power to the other end... much like the problem when one side is spinning and the other side isn't getting enough power to keep you going.

A part-time system is like having a locker between the front and rear axles, kind of what a locker inside the axle does for the left and right tires.

Jerry

Richard wrote:

Reply to
Jerry Bransford

I believe the big difference is with the full time on, any 'one' of 4 tires can be the main drive wheel, so when stopped and not using the brakes to vary the load, only one tire can be merrily spinning away.

If you put it into 'part time', the front and rear axles are locked so when stopped on ice at least 'two' wheels are spinning merrily away.

When this happens, you can hit the brake pedal and with some practice get both rear wheels spinning and sometimes even all 4 will break loose.

Torque goes to 'both' tires on one differential equally, so the one tire spinning loose has very little torque on it so the other side sits still. Hit the brakes or my owners manuals say you can use the emergency brake and you apply braking torque to the spinning wheel. This can get strong enough to match the traction of the stopped wheel so that the wheel on the other side will break loose and spin too.

Mike

86/00 CJ7 Laredo, 33x9.5 BFG Muds, 'glass nose to tail in '00 88 Cherokee 235 BFG AT's

Patrick wrote:

Reply to
Mike Romain

So a AWD Subaru would be better for every day driving in the snow ( city driving ) but very limited off-road ? Is that correct ? i have heard good thing about Subaru AWD latest generation.

"Mike Romain" a écrit dans le message de news: snipped-for-privacy@sympatico.ca...

Reply to
Patrick

Reply to
L.W.(ßill) Hughes III

Some consumer rating Subaru : 8.3/10

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Jeep :8.2/10
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These are user rating and not Manufacture or journalist.

The only thing is Subaru are expensive to fix while jeep is not very costy $$$

they have a good reputation around here however, better than AUDI$$$$$$$$

"L.W. ("ßill") Hughes III" a écrit dans le message de news: snipped-for-privacy@cox.net...

Reply to
Patrick

Actually I had a similar experience with my Grand Cherokee Laredo (Selectrac).

We've had a big snowstorm last week, so main streets are just wet, but side streets, alleys and parking lots can be snow covered.

One thing I've noticed for me anyway, is both Part Time and Full Time

4x4 do not seem to "fully engage" unless I'm rolling.

Why do I say that? On two occassions yesterday, the back wheels were slipping (once in an alley and the other as I tried to break into traffic from a snow covered parking lot driveway). I slipped, traffic was bearing down, I went into reverse to pull the vehicle back. Shifted to Drive, then put on Part Time 4x4 (light on) and tried again. Again, rear wheels slipped. So I waited for the red light to halt incoming traffic. :-) As I drove away I could feel it engage, in a few seconds.

Later that night I cut through an alley, started to slip, and put on the Part Time again. Initially the rear wheels continued to slip, then after like 30 feet, I could "feel" the 4x4 in the steering wheel, and then it gripped the snow.

I have a friend who has a Wrangler. I've been in it when we were stuck. Pull it into Part Time and it engages immediately.

Someone please tell me on Grand Cherokees with Selectrac (Part Time and Full Time), why does it seem like you have to be rolling for it to engage? I had it for a few years and it's always been that way.

Jim

Reply to
Jim Y.

I usually put the tranny in Neutral engage then reverse and then drive an it's engage. easier to unlock in reverse too. otherwise engage drive and within a few meter it will engage ! Why ??i have no answer.. !! BILL ?

Seem that the fulltime is better in driving mode that when stuck too. ?

I have 4 seasons tire however.

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Pat

"Jim Y." a écrit dans le message de news: lDjEd.13195$ snipped-for-privacy@newssvr19.news.prodigy.com...

Reply to
Patrick

It probably says in your manual that you need to be rolling for it to engage. Remember that gear teeth have to engage and can do that easier when the gears are moving.

My manual says I'm to be rolling a few kph.

Reply to
SteveBrady

I hope he has a clean shop rag handy ! ! ! Tom T

Reply to
Tom T

That must be something in the t-case that takes vacuum or time to change state.

With the Wranglers and old CJ's, the shift is instant. The YJ's and early Cherokees were vacuum lock on the front wheels and act like you describe.

Mike

86/00 CJ7 Laredo, 33x9.5 BFG Muds, 'glass nose to tail in '00 88 Cherokee 235 BFG AT's

Patrick wrote:

Reply to
Mike Romain

Not all 'full time' or AWD drives are even close to the same technologies!

'Limited slips' come into the transfer cases and diffs, dual trannies or drives, all kinds of things can be used.

99% of the vehicle performance is the driver....

Mike

86/00 CJ7 Laredo, 33x9.5 BFG Muds, 'glass nose to tail in '00 88 Cherokee 235 BFG AT's

Patrick wrote:

Reply to
Mike Romain

You can shift a Jeep into and out of 4x4 high at any legal speed. They started 'shift on the fly' back with the CJ's....

For 4x4 low, it still shifts better when going 2-3 mph for the reason given below.

Mike

86/00 CJ7 Laredo, 33x9.5 BFG Muds, 'glass nose to tail in '00 88 Cherokee 235 BFG AT's

SteveBrady wrote:

Reply to
Mike Romain

That's hysterical Thanks for the laugh TrailMarker

Reply to
carrollcaboodle

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