Center Locking Differential

65thKJ · **Posted:** Wed Feb 07, 2007 7:28 am

I was just comparing the Dodge Nitro to the liberrty and noticed that it has a mechanical locking center diff. According to ALLPAR, the liberty doesn't and even the Wrangler Doesn't and I was wondering why They wouldn't? Even my Ford Ranger had a center locking diff. Do the Jeeps have something different to help offroading?

Jeger · **Posted:** Wed Feb 07, 2007 8:43 am

The center diff is locked when in 4 part time and 4 low. The only time it is unlocked is if you are using 4 full time with the selec-trac transfercase or when in 2WD of course. I guess they didnt feel the need to advertise it as such, but they do illustrate this on the jeep website when you look at the 4x4 systems.

SnowgodCCR · **Posted:** Wed Feb 07, 2007 1:11 pm

Jeger hit it on the head, it's standard equipment on all jeeps (real jeeps anyway), and it's implied because of the trasfer case, so there really isn't much need to advertise it. My window sticker doesn't mention a center locking diff, and I've got a JK Rubicon :roll:

I must not have one then

Jeepjeepster · **Posted:** Wed Feb 07, 2007 2:09 pm

Every Liberty with 4wheel drive has a locking center diff.

Some older Grands didnt have one though which can have its Pros. Our 94 Grand has the Quadra-trac 1 4x4 system, which means that it cannot be put into 2wd. This is perfect for your everyday soccer moms that do not know how to use a transfer case. Its also good for pulling a boat or backing a boat up a hill at a slow speed, which we do all the time since we live on a big hill. Keeps the tranny alot cooler and doesnt let the torque slip as much.

1stJeepKJ · **Posted:** Wed Feb 07, 2007 6:38 pm

I'd be willing to go as far as to say any truck or suv with a low range 4x4 option locks the center differential.

XJMA · **Posted:** Wed Feb 07, 2007 8:07 pm

A "center locking diff" is a fancy way of saying that something has all-wheel drive (full-time 4) and real 4wheel drive (part-time).

A vehicle with all wheel drive, or full-time 4 has a differential in the transfer case (sometimes this differential is accompanied by a viscous coupling, not always).

Vehicles with real 4wheel drive do not have a differential in the transfer case, they have real 4x4, which just means that both the front and rear driveshafts spin at the same speed no matter what. Real transfer cases don't have diffs in them...so no one talks about "center locking diffs."

If you have the "select-trac" NP/NV 242 (ie. full-time and part-time 4) then you have a "center locking diff."

If you have the "command-trac" NP/NV 231 (ie. part-time 4) then you just have a true 4wheel drive transfer case. There is no diff in the transfer case (center, hehe) so you can't lock or unlock it. It's always "locked."

Some of the quadra-trac transfer cases are weird and have basically a limited slip in the transfer cass, called a viscous coupling, that limits the slip in the "center diff." When you are in part-time, the "center diff" is locked.

I hope this explains things to people and doesn't confuse them more!! Remember, most of the jargon you hear in advertisements and from people at dealerships is just clever marketing terms. There is 4wheel drive, and all-wheel drive. Some vehicles have both. If someone is talking about their 4/all wheel drive system and doesn't know that there is a difference, they dont' know what they are talking about, so don't buy anything from them!!

XJMA · **Posted:** Wed Feb 07, 2007 8:09 pm

Jeepjeepster wrote:

Every Liberty with 4wheel drive has a locking center diff.

Some older Grands didnt have one though which can have its Pros. Our 94 Grand has the Quadra-trac 1 4x4 system, which means that it cannot be put into 2wd. This is perfect for your everyday soccer moms that do not know how to use a transfer case. Its also good for pulling a boat or backing a boat up a hill at a slow speed, which we do all the time since we live on a big hill. Keeps the tranny alot cooler and doesnt let the torque slip as much.

Those older quadra trac systems do infact have a locking center diff. they just don't have a 2wheel drive option!! When you're in part-time, the center diff is locked. Same thing in 4lo, which is also part-time.

If you ahve one of those transfer cases, never drive it with the front driveshaft removed...it will ruin the viscous coupling, which costs more than a new transfercase to replace!! Also, those VCs usually go around 100k if the Tcase fluid hasn't been changed regularly. Just swap in an NP231 or NP242 and your problems are solved!

tjkj2002 · **Posted:** Wed Feb 07, 2007 8:10 pm

Ding,ding,ding,ding you hit it dead on :mrgreen:

.

XJMA · **Posted:** Wed Feb 07, 2007 8:13 pm

tjkj2002 wrote:

Ding,ding,ding,ding you hit it dead on :mrgreen:

.

Well, someone else may have been able to put it correctly in less words...but it seemed like there were a few people who weren't quite sure.

65thKJ · **Posted:** Wed Feb 07, 2007 10:39 pm

Thanks for clearing it up for me. I knew it didn't make sense but I just didn't know the terminology and differences regarding transfer cases.

Jeepjeepster · **Posted:** Wed Feb 07, 2007 11:54 pm

XJMA wrote:

Jeepjeepster wrote:

Every Liberty with 4wheel drive has a locking center diff.

Some older Grands didnt have one though which can have its Pros. Our 94 Grand has the Quadra-trac 1 4x4 system, which means that it cannot be put into 2wd. This is perfect for your everyday soccer moms that do not know how to use a transfer case. Its also good for pulling a boat or backing a boat up a hill at a slow speed, which we do all the time since we live on a big hill. Keeps the tranny alot cooler and doesnt let the torque slip as much.

Those older quadra trac systems do infact have a locking center diff. they just don't have a 2wheel drive option!! When you're in part-time, the center diff is locked. Same thing in 4lo, which is also part-time.

If you have one of those transfer cases, never drive it with the front drive shaft removed...it will ruin the viscous coupling, which costs more than a new transfer case to replace!! Also, those VCs usually go around 100k if the Tcase fluid hasn't been changed regularly. Just swap in an NP231 or NP242 and your problems are solved!

Nope. The center diff does NOT lock.

Weve stayed up on the oil change. That jeep has 160k on it and its still on the stock VC. :wink:

Stock everything actually.

I believe that the transfer case could be called a differential even though some of them dont have the ability to let the torque go to the front or rear wheels as it pleases. It still splits the torque front and rear, which makes it a diff. My thoughts could be wrong on that though.

XJMA · **Posted:** Thu Feb 08, 2007 2:11 pm

Jeepjeepster wrote:

XJMA wrote:

Jeepjeepster wrote:

Every Liberty with 4wheel drive has a locking center diff.

Some older Grands didnt have one though which can have its Pros. Our 94 Grand has the Quadra-trac 1 4x4 system, which means that it cannot be put into 2wd. This is perfect for your everyday soccer moms that do not know how to use a transfer case. Its also good for pulling a boat or backing a boat up a hill at a slow speed, which we do all the time since we live on a big hill. Keeps the tranny alot cooler and doesnt let the torque slip as much.

Those older quadra trac systems do infact have a locking center diff. they just don't have a 2wheel drive option!! When you're in part-time, the center diff is locked. Same thing in 4lo, which is also part-time.

If you have one of those transfer cases, never drive it with the front drive shaft removed...it will ruin the viscous coupling, which costs more than a new transfer case to replace!! Also, those VCs usually go around 100k if the Tcase fluid hasn't been changed regularly. Just swap in an NP231 or NP242 and your problems are solved!

Nope. The center diff does NOT lock.

Weve stayed up on the oil change. That jeep has 160k on it and its still on the stock VC. :wink:

Stock everything actually.

I believe that the transfer case could be called a differential even though some of them dont have the ability to let the torque go to the front or rear wheels as it pleases. It still splits the torque front and rear, which makes it a diff. My thoughts could be wrong on that though.

I wouldn't call a transfer case a differential because it can not differentiate anything. It either puts the power to one driveshaft, or two driveshafts. To differentiate, it would have to be able change the amount of power that it's putting out between the two driveshafts.

Oh, and my bad about the 249. I guess I got Tcase confused. I guess that's why everyone swaps em out! Here's a link if you want to get rid of the 249 http://www.4x4wire.com/jeep/tech/xfer/249-231/

Jeepjeepster · **Posted:** Thu Feb 08, 2007 3:04 pm

XJMA wrote:

Jeepjeepster wrote:

I wouldn't call a transfer case a differential because it can not differentiate anything. It either puts the power to one driveshaft, or two driveshafts. To differentiate, it would have to be able change the amount of power that it's putting out between the two driveshafts.

Oh, and my bad about the 249. I guess I got Tcase confused. I guess that's why everyone swaps em out! Here's a link if you want to get rid of the 249 http://www.4x4wire.com/jeep/tech/xfer/249-231/

Ahh, yea, I see what you are saying by it not really differentiating anything.

Thanks a bunch for that link! Im counting the days till that thing needs to be replaced. Amazes me that the TC and the tranny are still going. Weve pulled a boat with that thing too. :shock:

XJMA · **Posted:** Thu Feb 08, 2007 8:16 pm

Jeepjeepster wrote:

XJMA wrote:

Jeepjeepster wrote:

I wouldn't call a transfer case a differential because it can not differentiate anything. It either puts the power to one driveshaft, or two driveshafts. To differentiate, it would have to be able change the amount of power that it's putting out between the two driveshafts.

Oh, and my bad about the 249. I guess I got Tcase confused. I guess that's why everyone swaps em out! Here's a link if you want to get rid of the 249 http://www.4x4wire.com/jeep/tech/xfer/249-231/

Ahh, yea, I see what you are saying by it not really differentiating anything.

Thanks a bunch for that link! Im counting the days till that thing needs to be replaced. Amazes me that the TC and the tranny are still going. Weve pulled a boat with that thing too. :shock:

Jeep Power!! yeah! You must take good care of it! Tranny cooler, right?

Jeepjeepster · **Posted:** Thu Feb 08, 2007 9:10 pm

ohh yea, its got a tranny cooler. Both in the engine radiator and also an aux cooler.

XJMA · **Posted:** Fri Feb 09, 2007 3:23 pm

Jeepjeepster wrote:

ohh yea, its got a tranny cooler. Both in the engine radiator and also an aux cooler.

They work wonders! Worth their weight in gold IMO.

If everyone who owned a ZJ with that tranny/tcase setup had a tranny cooler (I don't count the line going through the radiator as one...) then there probably wouldn't have been so many people with problems. Then again, DC and other private shops would not have made money fixing them.

Center Locking Differential

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