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Unread 02-25-2010, 04:37 PM   #1
enrico1
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4WD Speed

Hi there, this might be a stupid question this is my first 4WD car. In 4WD mode how fast can you go not to do any damage?

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Unread 02-25-2010, 04:51 PM   #2
krawler510
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I'm guessing here, but almost every owners manual for any 4x4 prints 55mph max(for shifting into it at least). However, I doubt(hopefully) you'll want to go that fast on snow but maybe on the beach.

Either way, see what your owners manual says. And DO NOT drive it on pavement, dry or wet unless it is snow covered/icy.

(If you have full time 4x4 you are free to drive as your please)

Also, for 4 low keep the speeds down much more. That is just for serious pulling power on trails, hills, boat ramps for me.
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Unread 02-25-2010, 04:55 PM   #3
tjkj2002
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Well we can't say about a "car" but for your "JEEP" keep it under 55mph,if you need 4wd you shouldn't be driving that fast to begin with.

Full time 4wd-can drive on any surface

Part time 4wd is only for slippery surfaces only,wet pavement is NOT slippery enough for part time 4wd.
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Unread 02-25-2010, 04:56 PM   #4
jeepster09
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I agree with previous post. if you have Command Trac that is how you should use it. If however, you have Selectrac, you can put it in 4WD high and forget it. Can be driven on pavement at any speed.
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Unread 03-04-2010, 09:54 PM   #5
jebus_jeep
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I have the select-trac and I've found that in 4WD the front end has a strong vibration starting at 60 MPH. I thought it was a problem, but as one person put it "if you need 4WD at 60MPH, then you really shouldn't be going that fast"....he's right.
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Unread 03-05-2010, 07:24 PM   #6
enrico1
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thanks. I keep it under 50mph.
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Unread 03-07-2010, 01:09 PM   #7
ColdCase
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Quote:
Originally Posted by jebus_jeep View Post
I have the select-trac and I've found that in 4WD the front end has a strong vibration starting at 60 MPH. I thought it was a problem, but as one person put it "if you need 4WD at 60MPH, then you really shouldn't be going that fast"....he's right.
If the selectrac (automatic 4WD) has a vibration at any speed, you have a problem. The automatic selectrac does not engage 4WD fully unless there is wheel slip. Normally there just a small amount of tension on the drivetrain. This should not cause vibrations unless something is not working right.

Commandtrac is a manual transfer case and should not be driven in 4WD unless there is limited traction (snow - ice).
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Unread 03-07-2010, 07:10 PM   #8
tjkj2002
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Quote:
Originally Posted by ColdCase View Post
If the selectrac (automatic 4WD) has a vibration at any speed, you have a problem. The automatic selectrac does not engage 4WD fully unless there is wheel slip. Normally there just a small amount of tension on the drivetrain. This should not cause vibrations unless something is not working right.

Commandtrac is a manual transfer case and should not be driven in 4WD unless there is limited traction (snow - ice).
Not true,the select trac uses a "open" center diff in the t-case so the F/R driveshafts can turn at different speeds,going straight on a even traction surface you are sending torque to all 4 wheels.Just like a open diff with 1 tire on ice and 1 tire on dry pavement the torque will always follow the path of least resistance,the tire on ice will get all the power,same concept applies to the select trac t-case.
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Unread 03-08-2010, 05:28 AM   #9
ColdCase
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Quote:
Originally Posted by tjkj2002 View Post
Not true,the select trac uses a "open" center diff in the t-case so the F/R driveshafts can turn at different speeds,going straight on a even traction surface you are sending torque to all 4 wheels.Just like a open diff with 1 tire on ice and 1 tire on dry pavement the torque will always follow the path of least resistance,the tire on ice will get all the power,same concept applies to the select trac t-case.
No, the guy says he has a 2008 and its a KK. No KKs had an open dif case. Jeep changed cases in 2008. It is no longer an open diff, in fact it has no dif. The new case is just a regular case with a computer controlled clutch pack that variably locks 4WD sending torque to the front.. when the computer senses rear wheel spin.

Traction control, which applies brakes to a spinning wheel, supplements this new case thus allowing more torque to go to those wheels with some traction. With this system you can have two wheels, even three if physically possible, off the ground and still make progress, there is a U-Tube video around somewhere.
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Unread 03-08-2010, 05:52 AM   #10
tjkj2002
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Quote:
Originally Posted by ColdCase View Post
No, the guy says he has a 2008 and its a KK. No KKs had an open dif case. Jeep changed cases in 2008. It is no longer an open diff, in fact it has no dif. The new case is just a regular case with a computer controlled clutch pack that variably locks 4WD sending torque to the front.. when the computer senses rear wheel spin.
No computer controlled t-case in the KK,they are shifted via a electric motor but that is it.
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Unread 03-08-2010, 09:11 AM   #11
ColdCase
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Quote:
Originally Posted by tjkj2002 View Post
No computer controlled t-case in the KK,they are shifted via a electric motor but that is it.
You may want to check jeep.com they have a summary description there, or the shop manual that has a more detailed description. Both the command track and select trac II are shifted by electric motor. The selec trac is an active case design, however. The select track electric motor engaged clutch pack is controlled by the computer (although the computer is not mentioned in the marketing summary, the shop manual is clear).

Selec-Trac II supports the new MP 3022 two-speed, full-time active "on-demand" four-wheel drive transfer case. When driving in 4WD Auto mode, the transfer case clutch pack predicts conditions that may cause wheel slip and instantly applies increased or decreased torque between the front and rear axles based on real-time driving conditions, thus optimizing traction. Under the right conditions, the vehicle can be driven by just one wheel. For added capability when traversing steep grades, rough terrain, or extremely poor traction surfaces, the transfer case includes a 4WD Low mode. Electronic shifting between 4WD Auto and 4WD is accomplished via a console-mounted switch. A 2WD mode is also provided.

Command-Trac II® supports the new MP 1522 two-speed, part-time four-wheel drive transfer case, featuring smooth operation, shift-on-the-fly capability, and improved NVH control compared to systems with mechanical linkage. 2WD High is the usual driving mode, with the front driveline disengaged from the transfer case and power directed to the rear wheels. Selecting 4WD Lock via the electronic, console-mounted switch locks the front and rear driveshafts together; the two then rotate at the same speed and provide a 50 front/50 rear torque split, providing better traction on slippery surfaces. This transfer case allows for 2WD, 4WD high-range and low-range as well as neutral.
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Unread 03-08-2010, 12:49 PM   #12
krawler510
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Makes sense. It sounds like the exact same thing GM uses on its 'auto' 4x4 mode.
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Unread 03-13-2010, 12:48 AM   #13
AlterCow
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I have a 2008 KK auto and we were told to not exceed 50mph in 4wd Drive, but it would be best to not go over 45mph. We have been driving it with that in mind since 08 without any incidents with the tranny.

I have to echo the sentiment that "if you need 4WD at 60MPH, then you really shouldn't be going that fast"....
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