ARB/Truetrac arrangement

[goodburbon]

I've run
Front/Rear
Open/Open
Open/Trac-lock
Tru-trac/Trac-lock
Trutrac/E-locker
ARB/E-locker
Open/Detroit
Lockright/Detroit

Unfortunately the rig with the 242 has the 2 autolockers. For off-roading and maintaining streetability you can't beat the 2 selectable setup. Running a selectable rear/truetrac front allowed me to use the brakes to lock up the front, but I went through 2 ring gears, several shafts, and a few u-joints Using heavy throttle and brake to hold a lock. Since switching to selectables all around, I wheel harder and break less.

Being that the front brakes are a lot stronger than rear, I wouldn't think you'd be able to get a full lock out of a truetrac in the rear.

Here is an example of me with the truetrac front. You can see the wheelspin change as I change pressure on the brake pedal. The next time I attempted this obstacle, by the way, I lost a ring gear.:gee:

http://www.youtube.com/watch?v=EEjDQ5H0bK8

 

[spinnerdog]

Detroit rear Tru-Trac front not even noticeable. Detroit is fun in the rain. I took about three weeks to get the hang of it. After that wahoooooooooooo

 

[vegas_baja]

2000 with LPD30/C8.25. Front axle will be upgraded (shafts/u joints).

Do you plan on dumping the LP30 for a HP30? That would be my first move.
If money isn't an option, arb/arb.

 

[JoesXJ]

ARB/ARB FTW

 

[What Rd]

CAUTION! Driving on ice cream will not only cause your XJ to fold like a taco, but is also a primary cause of global warming. But if you must, ARB front and rear. :lecture: hasta

 

[Stihl029]

there is another option and that is get some real axles and a detroit and a no spin.

 

[Johnnie Walker]

I say.. ARB in the rear ans OX locker in the front.

 

[tooofast]

no matter what you pick a selectable in the front is fantastic and the most expensive option. I have a fill case Detroit in the rear and a ARB in the front of my Tj and find i only use the the ARB perhaps 5% of the time for about 10 seconds at a time. The fact i can lock the front when stating a climb or obstacle and then unlock it in a second to be able to really turn with ease is fantastic. The fact i can be in 4wd and not have my steering bind at all is great. Selectable is the best of both worlds, open for on the street and fire roads and the ablity go to go to full lock at a moments notice. Dont think that just because i dont use it much i dont need it. When i hit the ARB i am generally in a spot where there is not way to get up what im on without a front locker.
Being able to get up on a rock like this, then turn the locker off so i can do a full lock turn easy without dragging a wheel is worth every penny.

This may not look tough from this angle but here is the same spot with another ARB locked TJ doing it from a little further off..

I just priced out putting on in the XJ and with the labour (setting the gears) its about a $1000 which is nearly twice what i paid for the rig, and its still money well spend.

The a full case locker in the rear is far more forgiving on the street and i went Detroit as its pretty much fail safe, but im a tempted to do front and rear ARB's on the XJ.

Dave

 

[winkosmosis]

I've run
Front/Rear
Open/Open
Open/Trac-lock
Tru-trac/Trac-lock
Trutrac/E-locker
ARB/E-locker
Open/Detroit
Lockright/Detroit

Unfortunately the rig with the 242 has the 2 autolockers. For off-roading and maintaining streetability you can't beat the 2 selectable setup. Running a selectable rear/truetrac front allowed me to use the brakes to lock up the front, but I went through 2 ring gears, several shafts, and a few u-joints Using heavy throttle and brake to hold a lock. Since switching to selectables all around, I wheel harder and break less.

Being that the front brakes are a lot stronger than rear, I wouldn't think you'd be able to get a full lock out of a truetrac in the rear.

Here is an example of me with the truetrac front. You can see the wheelspin change as I change pressure on the brake pedal. The next time I attempted this obstacle, by the way, I lost a ring gear.:gee:

http://www.youtube.com/watch?v=EEjDQ5H0bK8

I don't get the full lock thing. A regular diff sends the same torque to both sides, but the Truetrac I think can send 5x to one side. So if you brake with a given force, the other wheel can get 5x that amount of torque

 

[JAS]

I am just finishing my rear ARB install. (the front is complete) If you have the front ARB then you already have the air line and air source. The second is not that much harder...

 

[goodburbon]

I don't get the full lock thing. A regular diff sends the same torque to both sides, but the Truetrac I think can send 5x to one side. So if you brake with a given force, the other wheel can get 5x that amount of torque

Not quite, a regular diff sends ALL of the torque to the side with the least amount of traction. A locker sents the same torque to both sides. A limited slip such as the truetrac sends a bit to the side that has more traction but most still goes to the side with less traction. This is where the brake pedal comes into play. You can simulate partial traction on the slipping wheel with the brake, forcing some torque to the tire with traction. The more brake you apply, the more equal the torque flow. If you watch the video I linked you can see the wheel in the air slow to almost the same speed as the crawl as I apply more brake, which would be a "full lock". If one wheel has zero traction while the other has some, and the wheels are receiving the same potential torque it is in effect a Locker . The problem is that this method is VERY stressful on drivetrain parts.

If I can clarify any further please let me know.:cheers:

 

[winkosmosis]

No, an open diff always sends the same torque to both sides. But if one wheel is in the air, the torque that can be applied is basically zero, hence zero torque goes to the other side also.

The Truetrac isn't a clutch pack LSD, but a torsen. It can send 5x (or whatever) torque to the wheel with traction. So if you have one wheel in the air, the other one will still get zero torque. If you apply brake, let's say 100lb/ft it gets multiplied and 500lb/ft goes to the other side. 100lb/ft will be used to overcome the brake on that side, and the other 400lb/ft for propulsion.

 

[goodburbon]

This isn't the place to debate this, and no one has even mentioned a clutch pack LSD until you. The point I am making is that the stress on drivetrain parts when trying to bias torque to a wheel with significantly more traction than another can be destructive. Will it work? Yes, until it 'splodes.

 

[Philprof]

thanks for the feedback...

 

[Vince]

My '93 has Truetracs front and rear, my '01 has ARBs front and rear.

I drive my '93 on the street in fulltime four wheel drive all the time. It gets the power down on the road without any fuss and always has predictable handling in any weather. Offroad, there's nothing to concern yourself with until you stop moving. The braking trick to get traction offroad works most of the time for tires 33" or smaller.

My '01 in fulltime on the street is OK, but it's not as good as my '93 particularly on wet roads. Offroad the ARBs have the edge, particularly on rocks. With Truetracs you don't have to think about traction until you lose it, with ARBs it's more anticipating loss of traction and remembering to do something about it.

I voted ARB/ARB. However, if I were to build another daily drive XJ with a 242 that was going to be used offroad (but not rockcrawling), I would probably go Truetrac/Truetrac. If you have a 231 transfercase you will never experience the benefit of a front Truetrac on the street so there's no point having one, go ARB in the front with a 231. If you've spent the money on providing compressed air then there's really not much point in not putting an ARB in the rear. If you put anything other than a selectable in the rear with an ARB in the front you will probably end up wishing you had ARBs in both.

 

[Goatman]

No, an open diff always sends the same torque to both sides. But if one wheel is in the air, the torque that can be applied is basically zero, hence zero torque goes to the other side also.

The Truetrac isn't a clutch pack LSD, but a torsen. It can send 5x (or whatever) torque to the wheel with traction. So if you have one wheel in the air, the other one will still get zero torque. If you apply brake, let's say 100lb/ft it gets multiplied and 500lb/ft goes to the other side. 100lb/ft will be used to overcome the brake on that side, and the other 400lb/ft for propulsion.

You need to quote your source, since you don't yet understand how it works AND you are quoting inaccurate info. There's no such thing as 5x times any torque, 5x what? A limited slip simply resists the axles turning at different speeds, so it applies some available torque (usually about 30%) to the wheel with less traction. And, how can an open diff always apply even torque if it applies no torque to the wheel with traction and all the torque to the wheel with no traction? A spinning wheel is getting nearly all of the torque, not zero torque. Let that spinning wheel, if it's in the air, come down on a hard surface all of a sudden and you'll see how much torque it was getting. You understand what's happening, you're just not saying it very accurately.

 

[aszaunmi]

ARB all around... I run em and love em F and B... don't need a selectable in the rear but it can be nice if you drive on the street...

 

[Goatman]

If I had to choose which axle to put a locker in, it would always be the front. A front locker does more on a trail than a rear locker, except on the steepest climbs, and even then you can pull the emergency brake a little to make the rear hook up. Selectable front and rear would be ideal, but to save some dough I'd go selectable front and LSD rear, which would be nice on the trail and on the street. I've run front locked and rear open and the other way around, and there is no comparison, front locked works MUCH better than rear locked, even on big obstacles and climbs. This summer running Swamp Lake trail, an easy trail but lots of rock, I ran mostly just in front wheel drive with the front locked.

The issues I see with a Truetrac are that it's expensive, still a full carrier diff, and they really aren't rated for use in the rear. We've seen them break in rear axle applications. It seems to me if you're going to spend that kind of money, you might as well get a locker. I think it's only another $100 to get a full Detroit rather than a Truetrac, still less than an ARB, and put the Detroit up front and the ARB in the rear. This would give you the best trail performance and the best street manners.

 

[winkosmosis]

You need to quote your source, since you don't yet understand how it works AND you are quoting inaccurate info. There's no such thing as 5x times any torque, 5x what? A limited slip simply resists the axles turning at different speeds, so it applies some available torque (usually about 30%) to the wheel with less traction. And, how can an open diff always apply even torque if it applies no torque to the wheel with traction and all the torque to the wheel with no traction? A spinning wheel is getting nearly all of the torque, not zero torque. Let that spinning wheel, if it's in the air, come down on a hard surface all of a sudden and you'll see how much torque it was getting. You understand what's happening, you're just not saying it very accurately.

I don't need to quote my source, because equal torque split is how a differential works, and multiplying torque is how a Torsen LSD works. That's why made it a point to say that the TrueTrac is a Torsen not a clutch LSD.
Here is a source though http://www.jeepforum.com/forum/f27/

You're thinking about the open diff wrong. Each side gets equal torque. If one wheel is in the air, it gets almost 0 ft lbs-- let's say 0.1 lb ft to overcome air resistance. That means 0.1 lb ft can go to the other side. No matter how much you rev your engine, the torque won't be greater than that. If you apply a cutting brake to the wheel in the air, the other wheel will get an amount of torque equal to the force you apply with the cutting brake.

A torsen is different in that it can send several times the torque to the wheel with traction. If one wheel is totally in the air, the other one won't get torque either (because 0 * 5 = 0), unless you apply brake.

 

[Goatman]

You're thinking about traction, not engine torque. If one tire is spinning while the other is not spinning, ALL of the engine power is going to the spinning wheel while none of the engine power is going to the non spinning wheel. But, they are applying equal force to the ground (traction) which is zero. Based on your explanation, the power the engine puts out disappears into thin air based on the action of the diff.....not possible, the power is there and will go through the diff, but it doesn't get to the ground unless there is enough traction. Also, with the Truetrac, it cannot multiply torque, it can only route it. The torque forces the pinion gears in the diff case to press against the case causing friction similar to a clutch pack, which resists one axle turning at a rate faster than the other axle, forcing some of the power to the axle with less resistance/traction. It cannot multiply torque, only route the torque that is applied.

And using Jeep forum as a source???

Silly argument, let the other readers decide.