Trac-Lock Differential - JeepForum.com

 
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post #1 of 15 Old 07-22-2002, 06:49 PM Thread Starter
Quebecman
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Trac-Lock Differential

I'm from Quebec, Canada, Kingdom of snow (french snow) and I'm looking to purchase a Liberty Limited with Select-Trac. I've never have a Jeep before (sorry) and I don't understand what is the benefit of the Trac-Lock option. I understand (...) that when I'm in Full-Time 4WD, the differential is locked in the center so I will get stuck if 2 wheels spin like the front left and the rear right, is that right or I'm a idiot?

Can somebody tell me what can happen if I don't have the Trac-Lock? Is it true that even with 4WD I can get stuck in the mud or snow because one wheel can spin? Is it true that Trac-Lock can prevent this?

Thanks!

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post #2 of 15 Old 07-22-2002, 07:28 PM
gonz165
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Basically, Jeep offers two four-wheel drive systems: part-time Command-TracŪ and full-time Selec-TracŪ. Selec-TracŪ has the added feature of a full-time mode that can be used year-round over any surface, whereas Command-TracŪ has to be manually disengaged if you're on regular street surfaces.

For a much better summary of various 4WD systems available, see here: http://www.cars.com/carsapp/national...ied/index.tmpl
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post #3 of 15 Old 07-22-2002, 07:36 PM
Liberty-4-All
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Re: Trac-Lock Differential

When in 4WD Full-Time ( for the road ), your transfer case is not locked. You KJ will be using one of the 4 wheels to propel you forward. If one starts to lose traction the power will be trasferred to one that has traction.

When in 4WD Part-Time ( for off-raod ), your trasfer case is locked so that one front and one rear wheel will turn at all times. With open diffs ( no trac-lok or locker ), if a wheel gets light and spins you do not get added traction on the other wheel ( same axle ).

With Trac-Lok it will sense that a wheel is loosing traction and transfer " some " power to the opposite wheel. This means that the two rear tires will both be working ( 2WD or 4WD ). When off-road the Trac-Lok will sense this loss of traction and " try " to compensate for it. If one rear wheel gets off the ground the Trac-Lok will not transfer power because it is receiving no input. You can " fool " the Trac-Lok by touching your brakes ( left foot while applying gas-much easier with an automatic ). This makes the Trac-Lok work even if the axle has one wheel off the ground.

This trick also works with open diffs but does not hook up as solidly as with a Trac-Lok. If you are going to attempt a steep climb that has some ruts, it is a good idea to pull the e-brake up three clicks before you attempt the climb ( just make sure you release the e-brake after you finish the climb ). If the e-brake is not enough you can give the foot brake a try with the left foot and it will engage both front wheels ( to a point ). Wiggling the front steering wheel will also help get both front wheels turning ( great for mud ).

02 Sahara Edition KJ
Best Mod...PowerTrax No Slip Locker
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Last edited by Liberty-4-All; 07-22-2002 at 07:39 PM.
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post #4 of 15 Old 07-23-2002, 07:26 AM Thread Starter
Quebecman
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OK I understand. Great explications.

Another question : does the Trac-Lock is ready to work all the time or only in Part-Time 4WD (Command-Trac)? What I mean is if I drive on Full-Time 4WD in winter and 1 wheel begin to spin on ice, does the Track-Lock will transfer some power to the 3 other wheels?
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post #5 of 15 Old 07-23-2002, 07:36 AM
Liberty-4-All
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Quote:
Originally posted by Quebecman
OK I understand. Great explications.

Another question : does the Trac-Lock is ready to work all the time or only in Part-Time 4WD (Command-Trac)? What I mean is if I drive on Full-Time 4WD in winter and 1 wheel begin to spin on ice, does the Track-Lock will transfer some power to the 3 other wheels?
Trac-Lok is a LSD ( limited slip differential ). It resides in your "rear" axle so it only affects your two rear tires. Since it resides in your rear axle, it always has power applied to it and works in all settings ( 2WD,4WD Part-Time, 4WD Full-Time ). An LSD in the rear can make driving on ice kind of tricky. It sometimes tends to make you spin out. It is not as big an issue with a KJ as with other short wheelbase vehicles in the Jeep line. With Selec-Trac engaged in Full-Time 4WD, you should have no problems. I have a Powertrax No Slip Locker in the rear and it works great with Full-Time 4WD in the wet.

02 Sahara Edition KJ
Best Mod...PowerTrax No Slip Locker
265/75/16 Maxxis Buckshot Mudders
ARMOR, ARMOR, ARMOR
LLL=15.75"
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post #6 of 15 Old 07-24-2002, 11:40 AM
MrEmoto
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Quote:
Originally posted by Liberty-4-All
I have a Powertrax No Slip Locker in the rear and it works great with Full-Time 4WD in the wet.
If you don't mind my asking, how much would I expect to pay to add a rear diff like that?

Thanks!

---------------------------------
Eventual Master of the Obvious #1

'02 Black Limited
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post #7 of 15 Old 07-24-2002, 11:49 AM
Liberty-4-All
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Quote:
Originally posted by MrEmoto


If you don't mind my asking, how much would I expect to pay to add a rear diff like that?

Thanks!
You can order them thru RockyRoadOutfitters or Rustys. They are about $350.00 plus shipping. Be sure to tell them if you have an open carrier or a limited slip ( different part numbers ). It is a "lunch box locker " so you will not need to set the backlash. With some mechanical skill you can install yourself in about 2-3 hours.

02 Sahara Edition KJ
Best Mod...PowerTrax No Slip Locker
265/75/16 Maxxis Buckshot Mudders
ARMOR, ARMOR, ARMOR
LLL=15.75"
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post #8 of 15 Old 09-12-2014, 06:33 PM
mmortiz9
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Command Trac-Track lok rear axle

I have Jeep Grand Cherokee 1993.This has Command Trac transfer case. I want to know if this grand cherokee has "trac-lok rear axle ?
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post #9 of 15 Old 09-12-2014, 08:15 PM
RockRollin
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As mentioned, trac-loc is only a LSD. It can be paired with select or command trac. The best option in snow is part time 4wd. Part time gives you a center LSD. The center LSD is what Jeeps outstanding traction legend is based on. Full time, or locked center diff can cause a break in traction on its own (why its not recommended for dry pavement). Honestly any 4wd Liberty is going to take good care of you in the snow, provided you have decent tires. My first KJ had the trac-loc and it was very squirrley if I got on the gas in the snow. I do miss it on the trails though.

"I like fun" Edd
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post #10 of 15 Old 09-14-2014, 02:57 AM
Billwill
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Quote:
Originally Posted by mmortiz9 View Post
I have Jeep Grand Cherokee 1993.This has Command Trac transfer case. I want to know if this grand cherokee has "trac-lok rear axle ?
You can look for a label on the rear axle...may tell you if it has Trac Lock....don't know if it was even invented by 1993!

Trac Lock needs a fair amount of attention as special Mopar Friction Modifier has to be added to the diff at the time of a diff oil change so if this has not been done for some years now then your Trac Loc is now a "Trashed Loc" as many people call it.....it does not have a very good reputation...I have it on my 2002 Export CRD and have changed the rear diff oil and added the Mopar Friction Modifier and have had no problems though!

As stated...Trac Lock is in the rear diff and has nothing to do with the transfer case being Command Trac or Select Trac!

2002 2.5 Export CRD Manual 5 speed.
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post #11 of 15 Old 09-14-2014, 05:27 AM
tjkj2002
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Quote:
Originally Posted by RockRollin View Post
As mentioned, trac-loc is only a LSD. It can be paired with select or command trac. The best option in snow is part time 4wd. Part time gives you a center LSD. The center LSD is what Jeeps outstanding traction legend is based on. Full time, or locked center diff can cause a break in traction on its own (why its not recommended for dry pavement). Honestly any 4wd Liberty is going to take good care of you in the snow, provided you have decent tires. My first KJ had the trac-loc and it was very squirrley if I got on the gas in the snow. I do miss it on the trails though.
Got it backwards,part time 4wd "locks" the t=case so the front and rear driveshafts spin at the same speed so a no-go on pavement.Full time 4wd is the one you can use on pavement since it's a "open" diff inside the t-case allowing the F/R driveshafts to spin at different speeds.

'02 Liberty sitting on 35" tires,HP44,RockJock60,and AtlasII t-case
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post #12 of 15 Old 09-14-2014, 06:01 AM
RockRollin
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Yea, dangit. I constantly get that backwards. Full time you can RUN full time, not locked full time.
Something about my old Dodge with 4hi/4hi-loc has tainted my brain. Thanks for clarification tjkj.
Anyway, the option using the center LSD "Full Time" proves better in snow personally.

"I like fun" Edd
Clawed: 90GW, TFI, Streetfire, 3"lift all spring, 31"BFG ATs, working RKE, Edel2131, Holly 1850, mild cam,
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post #13 of 15 Old 10-24-2015, 12:55 PM
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Hi,
I am new to Jeep forums. I have a 2006 KJ CRD Sport with Autobox and Selecttrac and a rear LSD.
I went off road today - in Cornwall England - to test the grip of this Jeep compared to the old Daihatsu Fourtrak/Rocky which we had before.
I set the transfer box to 4 Lo.
On a 40 degree grass/gravel hill the Jeep could drive no further than one car length in forward gear because the front RH tyre was turning/slipping on the grass. The other three wheels were stopped.
I turned around, and tried to reverse up the same slope. Again the front right was the only wheel turning, and the vehicle stopped after one car length. The Daihatsu could drive straight up this bank in forward or reverse - no problem.
Can you experts advise on what tests to do, and what to investigate next. I need this vehicle to tow big boats - see www.explorermarine,co,uk - off a muddy/sandy beach and I do not want to get stuck as we have an 8 metre - 25 foot tidal range!
Your advice please?
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post #14 of 15 Old 10-24-2015, 01:28 PM
u2slow
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The performance you describe with the LSD (trac-lok) is typical. You probably want to look at installing a proper axle locker (ARB, OX, Detroit, Aussie, Lockright, Spartan, No-Slip, etc.)
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post #15 of 15 Old 10-24-2015, 04:49 PM
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Quote:
Originally Posted by hughmattos View Post
Hi,
I am new to Jeep forums. I have a 2006 KJ CRD Sport with Autobox and Selecttrac and a rear LSD.
I went off road today - in Cornwall England - to test the grip of this Jeep compared to the old Daihatsu Fourtrak/Rocky which we had before.
I set the transfer box to 4 Lo.
On a 40 degree grass/gravel hill the Jeep could drive no further than one car length in forward gear because the front RH tyre was turning/slipping on the grass. The other three wheels were stopped.
I turned around, and tried to reverse up the same slope. Again the front right was the only wheel turning, and the vehicle stopped after one car length. The Daihatsu could drive straight up this bank in forward or reverse - no problem.
Can you experts advise on what tests to do, and what to investigate next. I need this vehicle to tow big boats - see www.explorermarine,co,uk - off a muddy/sandy beach and I do not want to get stuck as we have an 8 metre - 25 foot tidal range!
Your advice please?
In 4-LO you should have at least one wheel on the opposite axle spinning with that right-front wheel. In 4-LO the front and rear axles are locked together so something doesn't seem right. Even with an inoperable LSD at least one wheel should spin on that axle.

Does your Jeep have EAS or any of the other electronic traction aids? I'm wondering if something is acting up...

Bob

2003 Renegade, Black
- 3.7L, 42RLE, 4.10's, ARB Bull Bar, Smittybilt XRC 9500lb Winch, 4X Guard Trans skid, Factory Engine, T-case, Tank skids, Custom BoulderBars, JBA Front Coilovers, OME 948 rear, Bilsteins, JBA A-Arms, Moabs with Goodyear Duratracs 265/70-16
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