I tested out my front and rear Detroit Truetrac LSDs

[Steel City 06]

The grandpa technique helps but not much, if at all, if you're in difficult conditions. I used braking technique EXTENSIVELY when I had f/r Detroit Truetracs and it only helped some in easier situations. It became pretty much completely ineffective when I got onto tougher trail conditions that lifted a tire up off the ground. I ended up replacing both of them with lockers and never looked back.

Definitely agree with you here. The parking brake trick only works on the rear axle. You can use the service brakes to engage both axles, but it will take a lot of torque to power through those brakes. It will also be quite difficult to control, and probably rather jerky.

 

[Steel City 06]

To expand on my previous post:

Modern traction control systems brake only the spinning tire in either of those scenarios. This helps all types of differentials except for the locked locker.

Let’s say the traction control sees a wheel spinning and engages the brake at 100 ft-lbs on that wheel.

The open differential, with its 1:1 bias, now can deliver an extra 100 ft-lbs to the pavement. The same happens with the clutch-driven limited slip, and that extra effect is added to the torque provided by the clutches.

The locker is unaffected, and is actually impaired by the braking. But assuming it is functioning properly in the first place, the traction control cannot sense slippage and thus should not brake a wheel independently.

The gear-driven limited slip multiplies that resistance, and now it can deliver an extra 350 ft-lbs to the wheel on the pavement solely from the action of the brake.

Gear-driven limited slips in combination with modern traction control can do impressive stuff, often almost to the same level as a locker. Even modern cars with open differentials and powerful traction control systems can be rather impressive.

But without the capability to independently brake a wheel, a locker always has the ultimate capability.

 

[Steel City 06]

Looking at the various helical gear limited slip differentials out there, it looks like there are several options for the Dana 44.

Eaton offers the Detroit Truetrac, which has a bias ratio of around 3:1.

Torsen offers two different options. The T-2 has a bias ratio of 2.5:1 and the T-2R has a bias ratio of about 4:1.

More aggressive ratios will result in increased off-road performance, but also increase the risk of handling quirks. It’s not uncommon to put a higher ratio in the rear than the front.

 

[Jerry Bransford]

... It's not uncommon to put a higher ratio in the rear than the front.

It is uncommon in my personal opinion.

 

[pagrey]

Gear driven lockers like the trutrac don't lock spinning, they lock static. That 3:1 ratio is when the case is locked with pressure from the helical gears, once it starts to spin all torque goes to the free wheel and that's why Grandpas trick doesn't work, it never has. When the gear driven locker has one wheel spinning the 3:1 torque rating is meaningless.

 

[TJRick]

As much as I had front wheels in the air, from traction stand point, truetrack would be the last thing I put in front.
Truetrack in the back and selectable in the front, that is different story.

I like the way you think - a Detroit Tru-Trac limited slip in the rear and a locker in the front. That sounds like a smart build for someone with a stock Dana 35 in the back and a Dana 30 in the front.

Why don't more people do this? I mean, the Dana 35 can handle the limited slip, and isn't the Dana 30 strong enough to handle a locker up to at least 33" tires?

 

[Jerry Bransford]

Gear driven lockers like the trutrac don't lock spinning, they lock static. That 3:1 ratio is when the case is locked with pressure from the helical gears, once it starts to spin all torque goes to the free wheel and that's why Grandpas trick doesn't work, it never has. When the gear driven locker has one wheel spinning the 3:1 torque rating is meaningless.

So it doesn't cause confusion, the Truetrac is a gear driven limited slip differential. It's not even close to being a locker.

 

[Steel City 06]

One of the primary disadvantages of a Truetrac in a Dana 35 is that there is no compatible Super 35 carrier. Essentially you have to live with the stock weaker 27-spline shafts, whereas with a selectable, you can upgrade to the stronger shafts.

The new shafts themselves are only a small cost. Since you’re already buying a carrier, there really is no reason not to go Super 35.

 

[TJRick]

One of the primary disadvantages of a Truetrac in a Dana 35 is that there is no compatible Super 35 carrier. Essentially you have to live with the stock weaker 27-spline shafts, whereas with a selectable, you can upgrade to the stronger shafts.

The new shafts themselves are only a small cost. Since you’re already buying a carrier, there really is no reason not to go Super 35.

Will the weaker 27-spline shafts in a stock Dana 35 be a problem with a Detroit Tru-Trac limited slip differential?

 

[Jerry Bransford]

Will the weaker 27-spline shafts in a stock Dana 35 be a problem with a Detroit Tru-Trac limited slip differential?

Not in my experience using it with 33" tires. That is the biggest size tire that a stock Dana 35 doesn't usually have problems with. That's not to say the stock shafts haven't broken with 33" and even 30-31" tires if the driver is overly stupid/aggressive.

 

[TJRick]

Not in my experience using it with 33" tires. That is the biggest size tire that a stock Dana 35 doesn't usually have problems with. That's not to say the stock shafts haven't broken with 33" and even 30-31" tires if the driver is overly stupid/aggressive.

That's fair.

So why isn't the Dana 35/Tru-Trac limited slip in the rear combined with a Dana 30/locker up front combination suggested more often?

 

[Jerry Bransford]

That's fair.

So why isn't the Dana 35/Tru-Trac limited slip in the rear combined with a Dana 30/locker up front combination suggested more often?

Possibly because many of us believe the Truetrac does nothing useful when offroad on trails that are uneven enough to lift tires up off the ground.

 

[TJRick]

Possibly because many of us believe the Truetrac does nothing useful when offroad on trails that are uneven enough to lift tires up off the ground.

I understand that. But how often do the rear tires lift up compared to the front tires?

If you can only have one locker - or in the case of someone who has the weaker Dana 35 in the rear - wouldn't it make more sense to have a locker in the front than rear?

 

[Jerry Bransford]

I understand that. But how often do the rear tires lift up compared to the front tires?

If you can only have one locker - or in the case of someone who has the weaker Dana 35 in the rear - wouldn't it make more sense to have a locker in the front than rear?

With a stock Dana 35 the only axle that should have a locker in it is the front.

 

[pagrey]

So it doesn't cause confusion, the Truetrac is a gear driven limited slip differential. It's not even close to being a locker.

Very true, poor choice of words, in all cases lock was meant as "lock up" your brakes or stop slipping relative. Trutrac will transfer three times the torque to the high traction side before they start slipping. Eaton calls it wedging the pinion in the pocket.

 

[jjvw]

I understand that. But how often do the rear tires lift up compared to the front tires?

...

About 50/50

...

If you can only have one locker - or in the case of someone who has the weaker Dana 35 in the rear - wouldn't it make more sense to have a locker in the front than rear?

I ran several seasons with a locked front and gear driven LSD rear. It worked well to a point. A locked front doesn't affect steering much. That being said, when it counts, more traction comes from the rear during a climb due to weight shift. A locked rear is going to get you further along and than just a locked front will. And the LSD is going to let tires spin eventually.

 

[deadbeat son]

I like the way you think - a Detroit Tru-Trac limited slip in the rear and a locker in the front. That sounds like a smart build for someone with a stock Dana 35 in the back and a Dana 30 in the front.

Why don't more people do this? I mean, the Dana 35 can handle the limited slip, and isn't the Dana 30 strong enough to handle a locker up to at least 33" tires?

This is exactly what I did. Eaton ELocker in front, TrueTrac in rear. 4.56 gears and 31s; it works very well for my use. Now you have another reason to like my Jeep other than my use of the stock steel wheels.

For the record, I plan to run it like this until it doesn’t work for me. Then I can go with a Super 35 setup with another ELocker.

 

[Mobusaki]

I have chromoly shafts front and rear.

I'm sure a front selectable locker is superior for ultimate traction, but I'd imagine a front TT is still better than an open diff for muddy trails while being completely transparent on the road.

I love my Trutracs (front and rear) but unless you plan to drive in 4-high on snowy roads I'd recommend a locker upfront (lunchbox if on a budget). I don't often put a wheel in the air, and I drive on snowy country roads a lot, so my TT's have served me very well so far. But they are not lockers.

 

[abart]

I'm in the minority and have had Trutracs f/r for about 17 years now and have zero interest in lockers. I lift a tire on occasion and have no issues keeping momentum but I don't do hardcore rock crawling and never will. I don't see the Truetracs as worthless but I know the limits and go about my business that way. I also don't worry about my Dana 35 exploding either but that is another argument altogether.

 

[pagrey]

I don't see the Truetracs as worthless

I don't think they are worthless at all, sometimes people give advice based on how they wheel and forget it might not suit everyone. I think most people are pretty good about saying things like, "if you lift a wheel" and that helps.