Lockers vs. TruTrack

[Prybry]

Tru-trac and factory Limited Slip not the same...

I've been running a Detroit Tru Trac in the front of my Jeep for nearly 10 years now... I can tell you it's different than a factory Trac Loc (dana)

The Trac Loc uses a series of clutch pads to tie right and left axles together... once the load to the tire (contact with ground) goes away the clutch is over easily over powered and the tire spins... adding force back by hitting the brakes has a marginal effect.

On the Tru Trac however, the axles are tied together via a complex gear system which is more of a torque sensing affair. When the lifted tire is in the air it will spin, but with the addition of braking the torque will transfer to the loaded tire and seems to stay there. Even once the brake is released.
Now it does not lock the axles together, they do have a chance to spin some independently which makes them safer on ice for example than a locker.
That's one reason they are standard equipment on a lot of emergency vehicles.

I also own a Dodge Power Wagon with electric lockers front and rear... I know the rear diff is a limited slip even when not activated... has made icy roads very scary at times. I wouldn't ever lock both front and rear on ice, it would slide sideways in a second... any amount of crown in the road or side wind would have you in the ditch in seconds.

One other note... I notice a huge difference in the PW with the front locker on, the turning radius is much reduced and what is left is very rough. You can even feel the binding at the steering wheel. Never feel the Tru Trac on the Jeep at all... ever.

 

[computeruser]

Many say they can't afford a selectable locker but think what an accident might cost you in the long run.

Interesting argument. The extra couple hundred bucks for an ARB over a LS or non-selectable locker would quickly be eaten up the first time you inadvertently put the @ss end of your vehicle into something it ought not be put into. This may not matter to the guys who trailer their rigs everywhere, but for the guy pulling a trailer in all weather or for the daily driver...

 

[Martinjmpr]

I was seriously contemplating an LSD in my Taco but the concerns about slippery or icy roads stopped me. Twice in LSD equipped vehicles I've experienced sudden and unexpected sideways slides. The first one (in my Monty) resulted in a minor accident and the second (in my 2wd Ranger) fortunately resulted in no accident but that was absolute luck as I spun across the center of Grand Avenue (Laramie's main East-West street) in the middle of the day, into the oncoming lane. Had there been traffic it would have been a serious accident, probably a head-on collision.

At the time I didn't know what caused the spinouts but that was before I really understood what an LSD could do. Now I've resolved to keep my diff open until I can put a selectable locker on it.

 

[The Adam Blaster]

It's interesting (to me) all the stories about slipping with lockers and LSD's on snow and ice.
I would personally rather be able to control the sideays motion in these circumstances with the application, or lack of, the gas pedal.
I've been in situations with my Dakota having a LSD, sitting on a flat icy parking lot or iced-over trail, and the rear right tire just spinning.
And the factory LS didn't improve traction while applying the brakes.

Of course, I am the driver of my vehicles 99.9% of the time, so I don't have to worry about my wife spinning out.

 

[R_Lefebvre]

Can we PLEASE differentiate this discussion between true LSD's and Detroit Lockers and the like which really are more like "randomly locking lockers". True LSD's, clutch packs, torsen, or viscous do not cause spin outs. There are many sports cars that use these diffs, Subarus and Audis for example, and nobody would suggest those cars perform poorly on ice or snow.

I've never driven something with a Detroit Locker personally, but from what I'm reading, it's probably one of the craziest automotive inventions ever. I have had a fair amount of experience with LSD's in cars, and there is no controllability problem at all.

I had a limited slip in my Dodge Dakota, and I got stuck a lot.

And which type of LSD was this? I'm guessing clutch pack, the weakest of the LSD's. They aren't as dangerous as a Detroit, they're just ineffective, and slightly compromise traction.

Even a limited slip differential can be dangerous on a wet road and even more dangerous with a short wheelbase vehicle. When both rear wheels spin you can loose control before you realize you are in danger. In the hands of an inexperienced driver a limited slip or other lockers can be very dangerous.

Again, what type? Detroit? Point granted. Torsen or Viscous LSD, the person probably shouldn't have a license anyway.

 

[cruiseroutfit]

Can we PLEASE differentiate this discussion between true LSD's and Detroit Lockers and the like which really are more like "randomly locking lockers".

Sure, but first you'll need to recognize that the "Detroit Locker" is NOT a LSD, it is a 100% locking differential

The "Detroit TrueTrac" is a LSD featuring a helical gear setup.

...Again, what type? Detroit?

Keep in mind Detroit (Eaton) made/makes ~10 different styles of locking and LSD differentials. Knowing which one your referring too makes all the difference.

 

[R_Lefebvre]

Ok, yeah, I guess that's what I meant but I forgot it was a "Detroit TruTrack". Anyway, you get my point. The Detroit Locker is a randomly locking differential, not an LSD.

 

[7wt]

So what's everybody's thoughts on a spider replacement locker like a Powertrax for a daily driver?

 

[cruiseroutfit]

Ok, yeah, I guess that's what I meant but I forgot it was a "Detroit TruTrack". Anyway, you get my point. The Detroit Locker is a randomly locking differential, not an LSD.

No, I don't get your point.

The Detroit Locker does not randomly engage, its behavior and locking points are very predictable, plenty of daily drivers running rear Detroit Lockers with no side effects attributed to their "random" behavior. Yes, there are driving side effect related to have a locker in the rear, but calling them random is misleading.

I don't have much seat time with a TrueTrac, but I'm yet to really hear any bad reports about them on a street-driven rig, not to say they don't have some undesired handling components but nothing like my experience with clutch style LSD's that are in fact somewhat random.

 

[eleblanc]

Here is me showing the difference between rear locker and none. (i have ARB). I doubt anykind of lsd would have help me there.

http://www.youtube.com/watch?v=GnbBFt1qm-s

 

[R_Lefebvre]

Predictable? You're turning a low friction corner, and trying to accelerate. At low throttle position, everything is fine, both tires are sticking, and it's differentiating. At some point as you apply power, the inside wheel begins to slip, and then diff immediately locks. Now you have no differentiation and the outside wheel comes unstuck and you get the oversteer that everybody complains about.

Is the vehicle uncontrollable? I don't think a good driver would have terribly much trouble, but there are a lot of bad drivers out there.

An open diff would just cause the inside wheel to continue spinning while the outside wheel maintains lateral traction, so you slowly proceed around the corner with the inside wheel spinning.

With a full locked diff, the lack of differentiation applies a stabilizing moment about the axle, which makes it harder to rotate the vehicle. You understeer through the turn, unless you give it enough gas to break the axle loose, then you get oversteer, but it's more controllable than the "random" onset of lock with the Detroit locker.

With a Torsen LSD, the outside wheel actually recieves 3 times more torque than the inside wheel. This actually helps to rotate the vehicle while also aiding forward progress. The inside wheel is actually less likely to begin slipping in the first place, since the diff automatically sends 3 times more torque to the wheel with more grip.

 

[cruiseroutfit]

Before I proceed, I must ask, have you personally spent much time behind the wheel of a vehicle equipped with a rear Detroit Locker?

Predictable? You're turning a low friction corner, and trying to accelerate. At low throttle position, everything is fine, both tires are sticking, and it's differentiating. At some point as you apply power, the inside wheel begins to slip, and then diff immediately locks. Now you have no differentiation and the outside wheel comes unstuck and you get the oversteer that everybody complains about.

Yes, predictable. The engagement behavior of a Detroit locker is very systematic in my opinion. Will you get oversteer and tire chirp/scrub as you manuever through a corner, aboslutely. But the action is far from "random", in fact a few days behind the wheel and you get to the point where you know and can "feel" the exact instant they will engage/diseengage. I would give the same description to an Aussie or LockRight style auto-locker. Their handeling characterisics become almost second nature to the driver and using them as a daily driver is a non-issue for most. Are there extreme cases, sure. Would I put a Detroit in the back of a rental Jeep or a rig driven by a non-suspecting driver on occasion? No. But for a seasoned driver that is investigating a traction device for their own daily driver I think they can be an excellent choice. Lets not base our criteria around a mythical "bad driver" as that would have zero pertinence to the original poster.

but it's more controllable than the "random" onset of lock with the Detroit locker....

You lead me to believe your experienes with the Detroit are the exception rather than the rule. I've driven dozens of Detroit equipped rigs including owning some of my own, your term "random" is simply misleading.

You've done a great job describing all the functions and happenings of the various traction devices, I don't take issue with those and in fact am very comfortable with all of them. Having sold, installed, owned, serviced and driven most of them over the the years... no qualm there. I simply take issue with your continued insistence that the engagement of the Detroit being "random" which in my experience is not the case.

 

[IslandRidge]

This topic has been beat to death... but here is a good read to stimulate the debate..

http://www.stu-offroad.com/misc/locker-1.htm

My favorite comment is "....I was going to get ARB's in front, but the hardcore guys in the club all took their ARB's out, tired of wiring and airline probs!"

I love the detroit in my jeep.. makes one less thing to worry about..

 

[Scenic WonderRunner]

Here is a good....one page tells all.

http://www.offroaders.com/tech/limited-slip-lockers-differentials.htm

~~~~~~~~

I still need a Locker. Every time I go down to the junk yards to look for a Toyota TRD Electric Locking 3rd Member....they don't have any. This would be my preference.

I'm about to give up and just put in an Aussie Locker.



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[7wt]

Nice link Mark.