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Unread 02-15-2007, 07:32 AM   #1
franx
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4wd speed limit...

hey guys,

as some know, this is my first Jeep.

I was wondering if there is a speed limit on the 4WD...

I was told by the dealer that we couldnt put it in 4wd when above 80km/hr ...

but can I go faster then 80 km/hr ?


thanks, frank

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Unread 02-15-2007, 07:40 AM   #2
UTAH
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According to the manual, you can shift from 2H to 4H at speeds up to 55 MPH/88 KH.

Once in 4H, there's no mechanical reason I can think of to limit your speed. However, I'd question if it would be safe to drive at high speeds when the roads are bad enough to warrant the use of 4-wheel drive.

Bill
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Unread 02-15-2007, 07:43 AM   #3
SecondTJ
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yes you can go faster than 55mph in 4wd, but if conditions are that bad that you need 4wd, you probably shouldn't be doing 55mph+
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Unread 02-15-2007, 07:53 AM   #4
franx
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perfect, thanks guys.

Well in Canada here, when its snowing, like it did yesterday... the 4wd is really good and I was really impressed.

The traffic was going a bit faster then the 55mph/80kmh.. so I was wondering if it was OK to go faster then the 80kmh....

Thanks for the help guys.

Frank
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Unread 02-15-2007, 07:59 AM   #5
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I'd be tempted to check on this.

All other 4wd's I've seen always have a speed limit in 4wd. This is because you have no central differential. Having 4wd active at high speed could cause steering and handling issues as well as be damaging to the vehicle.

If there's wasn't a limit why would Jeep bother with 2wd at all??

The only exception I can think of are Land Rovers (since the 90/110 model of the early 80's). All Land Rovers are full time permanent 4wd. They however have a central differential called "diff lock" which you engage for difficult terrain but it limits you to about 50-60mph for safe use.
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Unread 02-15-2007, 08:43 AM   #6
SecondTJ
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Quote:
Originally Posted by 300bhp/ton

All other 4wd's I've seen always have a speed limit in 4wd. This is because you have no central differential. Having 4wd active at high speed could cause steering and handling issues as well as be damaging to the vehicle.

If there's wasn't a limit why would Jeep bother with 2wd at all??
The open center differential allows the front and rear axles to turn independently with full time.

Jeep only offers part time systems on Wranglers. Because of this, when 4wd is engaged the front and rear axles are locked together. At low speeds this creates an issue in turning, and makes it potentially damaging on dry pavement.

The issue is at low speeds with 4wd, not high speeds. That is why there is 2wd. Driving at highway speeds in 4wd will not damage anything.
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Unread 02-15-2007, 10:50 AM   #7
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Quote:
Originally Posted by SecondTJ
The open center differential allows the front and rear axles to turn independently with full time.

Jeep only offers part time systems on Wranglers. Because of this, when 4wd is engaged the front and rear axles are locked together. At low speeds this creates an issue in turning, and makes it potentially damaging on dry pavement.

The issue is at low speeds with 4wd, not high speeds. That is why there is 2wd. Driving at highway speeds in 4wd will not damage anything.
So making a turn a 80mph won't call on need a central diff to split the power, even though the radius of the turn for each wheel will be different.

And I don't agree with your low speed theory either as 4wd is purposly designed to work at low speed such as in low range and rock cralwing or off roading on rocky surfaces can promote more grip and streering lock than simply turning round in the parking lot.
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Unread 02-15-2007, 11:01 AM   #8
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Quote:
Originally Posted by 300bhp/ton
So making a turn a 80mph won't call on need a central diff to split the power, even though the radius of the turn for each wheel will be different.

And I don't agree with your low speed theory either as 4wd is purposly designed to work at low speed such as in low range and rock cralwing or off roading on rocky surfaces can promote more grip and streering lock than simply turning round in the parking lot.
Your not going to be making a sharp enough turn at 80 mph that it's going to be an issue.

Low range is not street use, lol.

There is reason full time systems can work on dry pavement and part time shouldn't. There is a big difference between low speed driving on-road, and low speed driving off-road.

Put your Jeep in 4H, on solid dry pavement, and cut the wheels all the way, try making a u-turn. It is going to fight and resist you. Now if you are on the highway, on a snowy or really rainy day, and the high bends, you are not nearly putting the same force on the wheels turning because its at a much less angle.
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Unread 02-15-2007, 12:42 PM   #9
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SecondTJ is right, the front and rear wheels only have significantly different paths of travel during tight turns, turns you won't be making at 60mph.
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Unread 02-15-2007, 12:50 PM   #10
jeepers3
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It does 70mph in 4wd, over long distances, no problem.

Whether or not that is bad for it, or you shouldn't do it - I have no idea. But to me, there is no sense in having 4wd if you can't use it when you need to. Cruising down an icy road at 70mph seems like the perfect situation for it.

For what it's worth, I leave my rig in 4wd all winter long, although I occasionally put it in 2wd for a brief time in parking lots. I paid a lot of money for that 4wd, you bet your *** I am going to use it whenever there is a hint of ice and snow on the road. Why fool around?
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Unread 02-15-2007, 01:22 PM   #11
NaeKid
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I have always used 4wd when the conditions warrant it. I leave my Jeep in 2wd 99% of the time, but when driving on icy uphills I'll pull the lever.

One thing I noticed is that there seems to be more 4x4's in the ditch in winter. It could be that having all the wheels pulling equally gives you less time to react to a small spin out. With 2wd, I find that I have more time to react to changes in the road.

On a side note, every time that I was thrown into the ditch (gravel or snow covered roads) I was in 4wd. I haven't been ditched with my Jeep in 2wd yet.
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Unread 02-15-2007, 01:31 PM   #12
JK_Jeep
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In the manual,

4L Position
Four Wheel Drive Low Range—Locks the front and rear
driveshafts together. Forces the front and rear wheels to
rotate at the same speed. Additional traction and maximum
pulling power for loose, slippery road surfaces
only. Do not exceed 25 mph (40 km/h).
The “4WD Indicator Light” (located in the instrument
cluster) will illuminate when the transfer case is shifted
into the 4L position.
Shifting Procedure
2H to 4H or 4H to 2H
Shifting between 2H and 4H can be made with the
vehicle stopped or in motion. If the vehicle is in motion,
shifts can be made up to 55 mph (88 km/h). With the
vehicle in motion, the transfer case will engage/
disengage faster if you momentarily release the accelerator
pedal after completing the shift. Apply a constant
force when shifting the transfer case lever.
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Quote:
Originally Posted by sierraexplorer
Thanks, if it is that good than I'm sure that they can't sell it in California. Everything else is illegal in this state except the illegalsl
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Unread 02-15-2007, 01:34 PM   #13
JK_Jeep
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May as well add this from the manual,

2H Position
Rear Wheel Drive High Range — Normal street and
highway driving. Dry hard surfaced roads.
4H Position
Four Wheel Drive High Range—Locks the front and rear
driveshafts together. Forces the front and rear wheels to
rotate at the same speed. Additional traction for loose,
slippery road surfaces.
NOTE: This range should not be used during dry
pavement operation.
The “4WD Indicator Light” (located in the instrument
cluster) will illuminate when the transfer case is shifted
into the 4H position.
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Thanks, if it is that good than I'm sure that they can't sell it in California. Everything else is illegal in this state except the illegalsl
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Unread 02-15-2007, 01:35 PM   #14
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By the way, its nice to have the manual electronically,

http://www.jeep.com/owners/manuals.html
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Originally Posted by sierraexplorer
Thanks, if it is that good than I'm sure that they can't sell it in California. Everything else is illegal in this state except the illegalsl
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Unread 02-15-2007, 06:50 PM   #15
redrom01
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Ive deffenatly drivin at high highway speeds with my Jeeps in 4H. If theres lots of snow on the roads go for it.
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