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Unread 04-29-2010, 07:59 PM   #1
sebush3
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Command Trac vs. Select Trac II

Trying to decide between the two;

Any real world experience with Select Trac II Performance? I'm still a little weiry of the performance of "Always On" 4WD systems. Is it true 4x4?

What are the real differences vs. the Command Trac (other than being able to leave Select Trac II engaged vs. only using Command Trac in wet, snowy, muddy conditions)?

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Unread 04-29-2010, 08:42 PM   #2
pauld73
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Select Trac has special differential gears that can slip when the front and rear tires are turning at a different speed. Command trac handles this situation by the wheels themselves slipping. This is why you cannot run command trac on dry pavement....the wheels can't slip to equalize the axel speeds. Select trac can compensate for different axel speeds and so you can run 4wd on all road conditions. The jeep website has a good explination about the difference between Command Trac and Select Trac.

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Unread 04-30-2010, 06:26 AM   #3
sebush3
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Thanks for the explanation.

How does that translate into real world performance? Is Command Trac more capable as it has a locking differential, or is the performance the same?
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Unread 04-30-2010, 06:34 AM   #4
Elt31987
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The Command Trac isnt locking but ive heard its stronger and more capable. Its gotten me outta messy situations
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Unread 04-30-2010, 09:33 AM   #5
ColdCase
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Quote:
Originally Posted by pauld73 View Post
Select Trac has special differential gears that can slip when the front and rear tires are turning at a different speed.
Not exactly for the KK (2008 and newer), but close. The select tract does not have a differential like the older cases. It has a locking system to lock in the front driveshaft similar to the command trac except that the locking mechanism contains a clutch pack that allows slip. The amount of lock is variable and controlled by the computer. When the computer senses wheel spin, it will engage the clutch with more force. So in normal everyday driving in 2WD mode, there is not any difference between the two cases operation (some say the command trac may be stronger but I dunno). The select trac in automatic 4WD mode will engae a bit of the clutch, so you do feel it on turns and it does put more wear ant tear on the front end. The select trac will completely lock in 4WD low.

The select trac is by far the best case for the street, especially for those that want to set and forget. Run it all year round. Yes it is true 4x4 case and yes if the other drivers in the family forget to switch out of 4WD there will be no damage to the vehicle. That is one of the biggest advantage.

The traction control works the same on either system, uses brakes to slow down a spinning wheel. The optional system available on the grand cherokee and commander adds computer controlled locking difs, but those are not available on the KK.

If you are off roading in low range there is no difference in the KK case capability. In high range, either one will pull you through when only one wheel has traction. Get the selectrac if you can find one.
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Unread 04-30-2010, 09:58 AM   #6
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So does Selec-Trac II not also have a part-time setting, so it's always just in full-time?

The Select-Trac on my KJ has both full-time and part-time, which is really nice to have as I use both, and it's certainly not a lesser transfer case compared to Command-Trac.

EDIT... So I went to Jeep.com and answered my own question. I see that Jeep did get rid of the part-time option from Selec-Trac to Selec-Trac II, which is too bad. Probably if anything was to make it easier. My wife took some time to understand when to use part-time or full-time... Since that is the case, if my KK was going to be mainly city driven, I'd go with Selec-Trac as it has it's advantages for being able to have four-wheel drive on any road surface (like mixed winter roads). However if you live in the country and your winter driving is mostly snow covered roads and you adventure off-road more, I'd go with Command-Trac.
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Last edited by grogie; 04-30-2010 at 10:12 AM..
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Unread 05-02-2010, 07:28 AM   #7
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Quote:
Originally Posted by grogie View Post
So does Selec-Trac II not also have a part-time setting, so it's always just in full-time?

The Select-Trac on my KJ has both full-time and part-time, which is really nice to have as I use both, and it's certainly not a lesser transfer case compared to Command-Trac.

EDIT... So I went to Jeep.com and answered my own question. I see that Jeep did get rid of the part-time option from Selec-Trac to Selec-Trac II, which is too bad. Probably if anything was to make it easier. My wife took some time to understand when to use part-time or full-time... Since that is the case, if my KK was going to be mainly city driven, I'd go with Selec-Trac as it has it's advantages for being able to have four-wheel drive on any road surface (like mixed winter roads). However if you live in the country and your winter driving is mostly snow covered roads and you adventure off-road more, I'd go with Command-Trac.
The 4 low is a lock position. Select trac does not have a 4WD high lock position as you have found.

I've had both cases and I think you are wrong about the recommendation, the select trac is better on snowy roads and you don't need to keep shifting in and out when the road conditions change. The only conditions where a command trac with locking 4WD hi may offer better performance is in very deep (10 inch) snow or gravel.
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Unread 08-15-2010, 01:40 AM   #8
tr4petty
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If your wife drives the Liberty much, go with the Selec-trac. I she's anything like my wife, you'll never be able to make her understand when and where to use standard 4wd. The Selec-trac can be used on hard surfaces OR in mud/snow so she won't have to make that decision.
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Unread 08-15-2010, 10:42 PM   #9
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Quote:
So does Selec-Trac II not also have a part-time setting, so it's always just in full-time?

The Select-Trac on my KJ has both full-time and part-time, which is really nice to have as I use both, and it's certainly not a lesser transfer case compared to Command-Trac.

EDIT... So I went to Jeep.com and answered my own question. I see that Jeep did get rid of the part-time option from Selec-Trac to Selec-Trac II, which is too bad. Probably if anything was to make it easier.
Hold on. I know the Jeep website says "The next-generation Selec-Trac II 4WD transfer case is always active so you'll be ready for rocks or mud or anything in-between", but this is misleading. Some marketing know-nothing is misrepresenting reality.
Jeep - 2010 Jeep Liberty - Capability - Off-Road Performance

2WD is still the primary selector position in the Selec-Trac II transfer case. "4WD Auto" as it appears on the selector (in my 2010 KK) is essentially your part-time option to be Full-Time if you so desire. And then you have 4WD Low. Unlike the Quadra Trac II or Quadra Drive, the Selec-Trac II not always in 4-wheel drive. These latter two ARE full-time on-demand or basically all-wheel drive systems. I had the Quadra Trac II in my '99 Grand Cherokee. It was locked and loaded all the time.

Here's a good explanation of the various transfer cases minus the Selec-Trac II.

Jeep Grand Cherokee WJ - WJ Four-Wheel Drive Systems
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Unread 08-16-2010, 07:43 AM   #10
tr4petty
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If you go to www.jeep.com/en/4x4/how_systems_work/ it will explain each of Jeep's 4x4 systems including Selec-Trac II. The way it was explained to me, the Selec_trac II in 4wd Auto mode works like a full-time 4wd system with the added benefit of limited-slip axles in both ends. It can send practically all of it's power to one wheel with traction if the need arises or it can send most of it's power to the rear axle when on a dry hard surface. Supposedly, it does this by working with the ESP or stability control system.
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