I've been doing some research in hopes to put 1 or more lockers in my truck in the spring. I figure I'll do the lockers,regearing, and tires all at the same time. My goal for this post is to understand the mechanics of lockers as best as I can so that I (and the rare person who searches and finds this thread) can make the right choice based on my driving style. What I find when I read other threads are people just saying "rules" that they learned. Things like "you have to coast through a turn or it wants to drive straight" or something like that. That may or may not be the case, but "rules" don't let you understand what your equipment is doing, and understanding is how you get the best performance.

So, I've read the locker faq: https://www.yotatech.com/forums/f31/locker-faq-43572/. And I've been to Roger's page where he explains how a locker works: http://www.4crawler.com/4x4/TrueTrac.shtml#Locker.

Anyway, here's my take on things, and I hope that any mistakes in my understanding can be corrected.

Regular Open Diff - We all know this, but just for completeness, the torque applied to both wheels is equal, so the maximum torque any wheel can get is the minimum torque to make one of them slip. So when one wheel is in the air, you go nowhere. The (rotational) speed of the carrier gear is the average of the two wheels

Auto Locker - There is a ratcheting mechanism that allows one wheel to freewheel faster than the carrier gear, so the slowest one wheel can go is the speed of the carrier gear. So when going around a turn, the outside wheel is freewheeling and all the torque gets applied to the inside wheel. This makes things tricky if you get on the gas hard and cause the inside wheel to slip. But as long as the inside wheel doesn't slip, you should never notice anything wierd (except for the clicking sounds). What I'm not clear on is what happens in reverse? If wheels are allowed to free wheel, how to you transfer negative torque to the wheels (either driving in reverse, or engine braking, etc)

Selectable Locker - This is easy to understand, either electronics or pneumatics that are under control of the driver are used to swtich between open and locked.

Torsen Diff - These setups act like an open diff and the carrier gear is going the average speed of the wheels, but the maximum amount of torque that can go to any wheel is (depending on how it's designed) 3-5 times the amount of torque that makes any one wheel slip. So this is good as long as you don't have a wheel in the air beause 3*0 is still 0. However, you can apply the brake and you get a torque multiplication to help pull you along. I always thought that the Torsen type differential was patented and only available to specific applications, but after reading about the Detroit TrueTrac, that sounds like a torsen type differential, am I correct?

Limited Slip Diff - There's some type of extra set of clutches or something inside that detects when the wheels are moving at differet speeds. When the difference is above some threshold, they lock. I've never been too clear on a LSD. there are two senarios that I imagine, 1) when it locks, it just locks and it's as if you engaged a locker. or 2) the clutch packs add allow some extra torque to be transfered to the wheel with the most traction. So instead of saying that the maximum torque applied to any wheel is the minimum amount required to make one slip, I would say the maximum torque applied to any wheel is the minimum required to make one slip plus some extra that the clutch packs add.

Ok, so finally after all of that, what would you recommend for a daily driver truck that I also take off road. I don't take the truck off road to go rock crawling and stuff like that (I'd like to, but I don't have the budget to keep breaking things), I just go off road to get to hiking/biking/showshoeing trail heads. In the CO backcountry these trails can get pretty nasty, and I've been turned around before because of the lack of a locker. (or possibly my poor off road driving experience)

My initial idea is to put a truetrac (if it is indeed a torsen like diff) in both the front and back. Then if things get really bad and I have a wheel off the ground, I can play with the brake to get some extra torque.

Or would you suggest I put an Auto Locker or LSD in one of the axles, and if so which one. Having one in the back would be nice except for commuting on snowy roads, and one in the front may just making turning a pain when i'm in 4hi on the roads.

I appreciate opinions or corrections to how i think stuff works.

Thanks!

 

I had an open diff up until recently, and had a Detroit TrueTrac installed. I haven't tested it off the road, but I certainly noticed a difference driving in the raid and taking off from a stop under wet conditions. So far I love it and would recommend it for the price.

 

There is a link off the same page as my TrueTrac page is linked that has *everything* you wanted to know about lockers, limited slips, etc.:
- http://www.4crawler.com/4x4/4R_TechInfo.shtml#DiffInfo

TrueTrac is a TorSen type diff, that is is Senses Torque and sends torque to the wheel that has the most traction, up to it's torque transfer ratio, about 2.5-3.0:1 in the TT. I loved mine in the snow, really worked well and has the advantage that wheel slip is not required for it to operate. An autolocker will almost always spin or drive one wheel or the other in slippery conditions while turning. Normally the inside wheel will take all the torque (the outer freewheels). But if you overpower that wheel, it will spin and the outer will do all the driving. I've been in slick conditions with my old rear Detroit where the rear axle would oscillated between inside and outside tire driving up a wet, slippery hill with lots of turns. First the inside would break loose, then the outside grabbed. Then the inner wheel might find some traction and force the outer to freewheel. And this repeated back and forth all the way up for like 10 miles, a real PITA!

 

Truetracs are great but only for mild wheeling. If you get crossed up and lift wheels a lot, they are ok as long as you aren't climbing. You can use the ebrake to lock 'em up solid, but do so at the risk of breaking the TT and doing other fun things like twisting your axle housing and peeling off spring perches. (I know from experience....)

However, the on road manners of the TT are superb.

If you have the dough, a selectable locker is the way to go.

If not, a TT is good just limit yourself to like 50% of total e-brake. I had my e-brake on as hard as I could pull it to get up a nasty obstacle and did a lot of damage.

Frank

 

Sorry to hijack, Ok so here is a question for a IFS truck that would be a daily driver as well, wouldn't it make since to put a locker in only the front because then the tires would last longer since you wouldn't keep your hubs locked at all times and it would get less wear on the locker, or would just a rear be better in a IFS since the tires in the back come off the ground the most?

 

Usually you add a traction aiding diff to the rear axle first. This is because you get the most traction on the rear end, since you mostly need high traction going up something which means most of the weight has shifted to the rear axle. A front locker can help and with IFS, you are most likely to lift a front tire since the flex on the front end is less. A locker up front will affect steering when in 4WD, makes steering harder and turning radius larger. For a mostly daily drier, a limited slip diff is a good option, it'll help out in almost all driving, 2WD on pavement, wet, dry, icy, snowy, and in 4WD. If I were to build another truck for daily use and mild wheeling and snow driving, I would put TrueTracs front and rear.

 

I second Roger. I had TT's front and rear but now have a Supra Limited Slip in the rear differential. TT's work very well for snow, ice, medium wheeling, with excellent street manners.

Frank

 

just had my lock-right put in. love it. handles nice on the road and AWESOME off the road. i can do things in 2wd offroad that i couldnt do in 4 before. and its nice to know that those 2 rear wheels will ALWAYS be spinning. when i got the lock-right in the mail, i called up the company to make sure they sent me everything. there arent many parts at all...basically 2 little pieces that go together with 2 rings...and some screws/springs. its nice to think that theres that much less that can go wrong and need fixing.
my .02.

 

I recently installed Tru Trac's front and rear and I'm very happy with the results. After reading through the Detroit literature and doing some research I found a few interesting thing that you don't hear about often with tru tracs. Of all the tru trac's Detroit makes only 2 of them come with preload springs that "Preload" the diff and those are for the Toyota 8" and the Dana 35. With both of my rear tires off the ground it takes about 100 ft/lbs of torque to rotate my wheels in opposite directions. The other bit of info I dug up was that there was a recent change to the Toyota Tru Trac in that they now use a 3 pinion design instead of the old less effective 2 pinion for increased torque biasing. The front 7.5 is also a 3 pinion design but you can certainly feel the difference in the load springs when comparing it to the 8" model. The rear is almost invisible unless you get into the skinny pedal pretty hard in a corner then you can feel the tires lock up and if you keep at the skinny pedal in the rain you can get the full on sideways drift going. I have yet to hit the trail with my set up (need to find some people to wheel with) but I feel its more than ready now.

 

Sounds like they have made some good improvements to the TT since I got mine in '97.
I only wish they could figure out how to stuff the Elec-Trac into a drop-out 3rd member!

 

I guess could search but am not that great in differentiating truck parts yet. What would a TT cost for a rear diff? I'm probably regearing soon and the cost of labor would be free for the TT. BTW, I have a 3rd gen runner.

 

http://www.jawsgear.net/store/catalo...a&filter_id=18

$375.

one of the first sites that came up on a googled search.

 

Thanks.

 

I paid $330 for my v6 Tru-Trac from Rands Ring and Pinion just a month or so ago.