Limited Slip Faceoff: Detroit TrueTrac vs. ARB Air Locker


Am I the only one who shudders at the subject of this post, which starts "Limited Slip Faceoff:" and then specifies a Locker and a Limited Slip?? Differential faceoff is what I'd call it. I think I already have my $.02 in here somewhere. Enjoy your lockers and Limited slips fellow EXPO'ers!! :)


Haha head to head..... Lol.

I'll be running blended. Limited Slip truetrac rear. ARB front for when the SHTF.


West slope, N. Ser. Nev.
This is an excerpt of a piece about my complete drivetrain upgrade coming out in January/2017 on Truck Camper Adventure on line magazine for off-road style truck campers. Part of the upgrade was going from 3.54:1 gears to 4.10:1 gears to compensate for 35" tires and heavier steel wheels. I had a front True Trac already and a rear Power Lok, L.S. diff., but this was about to change to True Tracs on both ends.
"Sean at River City Differential told me on the phone that he had a lightly used set of Dana 60/Dana 80 RGP’s that he could install saving me a lot of cash on parts. The ring gear and pinion are always a married set. A used set needs no break in time. I motored down the hill to Sacramento @ 80 mph, for the last time, and left the truck off for him to do his magic. Actually, he only had the front Dana 60 used parts and had to install a new 4.10 Dana 80 RGP. Sean called and said my beloved Power Lok for the Dana 80 was now obsolete and no spare parts were available. The Power Lok would not fit on the thicker 4.10 carrier flange without a lot of machining anyway. He gave me a $350 credit for my old Power Lok, carriers, and RGP’s. All was not lost as he installed yet another Eaton Detroit True Trac in its stead. Actually I like it better as the tires do not chirp in tight corners and it is more transparent on the highway. The off-road manners are predictable and solid especially on slippery surfaces like ice and snow. The power just wanders seamlessly over to the tire with the most traction. No oversteer. No understeer.
I’m now in the middle of a break in period where I’m not going fast; nor accelerating harshly; and driving only 20 to 30 minutes at a time, followed by a cool down period for the RGP. There is some metallurgical mystery happening if the gears get too hot or have too much torque applied during the first 500 miles." Here's a short clip on a jeep trail near Mammoth, CA, using all my new drivetrain parts. You may have to click on the thumb.

jefe de doble tracción
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Y'all are making me want truetracs again!

Btw I have an air compressor, and it will be installed, but I'd still rather have truetracs for the simple reason that they rule 99% of the time, and they do damn well the remaining 1% of the time, whereas lockers only rule that 1% of the time.
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Happy Joe

Apprentice Geezer
Since starting to off road (more than a few moons ago) I have used, and sworn at, a great many differentials, ranging from open though limited slips and assorted lockers (so many that I had to learn to install gears and in (checkbook) self defense).
My Opinions (worth everything you pay for them);
Open diffs can work OK as long as you can keep nearly the same pressure on all tires making suspension and driving skill paramount.
Limited slips (Trac-locks and assorted clutch driven kin) definitely help a little, however as the clutches become worn they become less effective)..,still requiring suspension and driving skill to be (somewhat) effective.
Power-locks (self tightening clutch pack lockable limited slip) can lock up tight with sufficient torque application but will open if you let off the throttle on a hill or obstacle. Still, much better than track locks, govlocks (fragile, IMO) etc.
Spools, minispools and Lincoln lockers are best left out behind the barn, IMO. They have a place only on entry level stock cars and trailer Queens. They embody all that is worst about lockers besides wearing out tires on the street and while strong (Lincoln locker strength is highly variable) and workable (after a fashion, with quite large drawbacks) are the lowest class of "locker".
Automatic lockers (ranging from Detroit lockers down through lunch box lockers can be very effective and IMO should be chosen over selectable lockers for front differential use EXCEPT where slippery icy road/trail use is possible. Automatic lockers in slippery condition can make the vehicle much less controllable; spinning both tires at the least excuse and screwing the vehicle, often sideways, downhill/to the curb. They can also lock and release under certain conditions, where alternate tires become airborne (very mogully down hills, difficult to extreme terrain) giving a fair imitation of free fall; requiring a very educated brake foot. (my favorites are Detroit (soft) lockers, hopefully, the original is now obsolete). Lunch box lockers some times wear relatively quickly in rear axles in daily driven applications; so research carefully before purchase.
Selectable lockers have the advantage that the differential can be locked or open by the driver's decision, allowing slippery surfaces to be traversed (open) much more safely (nothing like an icy mountain side hill, next to a thousand foot drop, to convince people of this). In non slippery conditions they can excel in the strength and traction department, except that they make steering much less effective when installed in the front axle (have to release the locker, steer to even the wheel traction, to assure release, then steer in the wanted direction). My favorite are ARB airlockers (near 25 years of experience).
Since I'm getting even more antique and don't care for the very difficult to extreme trails anymore I am looking at trutracks as my next differential carriers, when they slip (according to my trusted sources) a little educated brake work can pull a vehicle through... we will likely see ...
Finally; electronic traction control these systems take much of the skill out of driving on non-level variable traction surfaces (a good thing for many) but in my experience on the more difficult/extreme trails and obstacles can often be surpassed by good driving and actual lockers on well set up vehicles.

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Before making a decision either way, make sure you really need one. If you are doing 5,6 trails (on a 10 scale) then you may not even need either one. Good driving skills can do a lot towards getting a fellow through some rough stuff. If you do find that you need something extra to get you through, then go with a rear first and again see how you do.
Airing down and skillful choice in choosing a line makes a big difference. My philosophy has always been not to add anything until I have a proven need. Of course I would not have had to fix my door if I had put on sliders before getting into rough stuff. But usually the wait and see method works well. I have followed some folks with open dif's, 31 inch tires and no lift and been very impressed with where they go. Good luck on your choice.
I generally agree with that kind of philosophy. However, if the OP knows he will be traveling moderately technical trails which are also remote, then selectable lockers are a very good to have, if not outright essential. Lockers are one of those mods that will go unused for the most part, but when you need them, they need to work well and are often the difference between getting stuck somewhere and crawling your way out. I've only had to use my rear locker a handful of times, but in almost all of those instances, I'm 99% sure that I would've gotten stuck if I did not have a locker. I equate them to fire extinguishers or life boats; you might wonder why you spend so much money on them for the limited use they seem to get, but when s%*t hits the fan, you'll be glad you've got them.

OP, if money isn't a limitation, get the ARB selectable lockers (I'd prioritize the rear over the front). Limited slips are decent, especially for the money you're paying. But if you are going to travel moderately difficult trails in remote areas, a locker will provide insurance that a limited slip just can't match. ARB has a good reputation for reliability, so if you're going to spend that kind of cash, I would spend it on ARB products.

Happy Joe

Apprentice Geezer
I know what you're saying. I've had LSD's on multiple vehicles and the NEVER, NEVER, worked worth a flip.
As the clutches, in most limited slip diffs, wear their ability to limit slip goes away, giving them performance ranging from anemic (new) to open. Use of excessive friction modifier additive in the differential grease also can reduce performance. Use of gear lube without the friction modifier, temporarily, greatly improves performance until the spider gears loose their teeth leaving people that do this faced with towing and replacement of both the diff and ring and pinion (damaged by spider gear teeth) along with the installation bill. Usually the performance of worn limited slip diffs can be brought back by replacing the clutches; though this can be PITA. Some improvement, over new stock, can be had by fitting an extra clutch into the packs (often requires lapping a used clutch plate until it can fit).



Hegelian Scum
Just to add my 2 cents:
I've driven a mechanical locked rear diff on the street as a daily. I'd much prefer the luxury of an air locker because you get all the traction when you want it and none of the hassles when you don't. The big risk is the air line and compressor. 10 cents worth of tubing can make the difference.

I would also say that the LSD is garbage and not an option for me, at least in a serious build. However, for a vehicle that being used selectively you can use an LSD with clutches and do okay in mildly technical stuff. And that's what OP is talking about here with their rig. I wouldn't be scared of an LSD in that case. Crawlers and stump jumpers are meaningless in terms of experience here where probably the bigger priority is to have a streetable vehicle that won't worsen mileage for 1 percent of the time having better traction. IMO, it's probably better to have LSD's and a winch than lockers, if you're on a tight budget. That's a lot of money you can spend on fuel instead of on diffs, and fuel takes you places that are fun.

So, if you're on a budget and not planning on crawling with a camper on a full size, LSD can be a good choice. But all LSD units aren't created equal either.

This spicer unit that comes stock in Dodge products, like my 2nd gen Ram, is absolute junk.

These coin style clutches will break and fall into the gears, potentially causing a rear to lock while you're doing highway speeds. I personally know of a couple of trucks that have experienced this due to these spicer units failing. I'm not here to throw rocks at Spicer. I'm just pointing out that you need to know the ins/outs of your diff, whatever you choose.

However, the Ford style LSD and others aren't fraught with the same problems.
I rebuilt this one and stuck it back in the beater, because it's a budget build and I wanted to road test the thing to make sure everything else worked. But the Spicer unit can't even really be serviced with parts like thrust washers and spiders, because Spicer wants you to buy a whole new unit. So, they will not sell you service parts like these. Very important to know, if you wrench and plan on being on the road, not just with an LSD but with a mechanical locker. Where do you get parts, and can you even get parts?

Certainly Yukon and Eaton do a good job with service components. But whatever you run, you should ensure that you A: know how to service it if the need arises in the backcountry or B: have AAA or whatever.

TL;DR: LSD can be a good choice, but choose a good one that can be serviced. Keep your 1000 bucks in your pocket for gas and go see stuff, do stuff, and camp near stuff, since your rig isn't a crawler and mileage or handling may be a bigger priority.

Happy Joe

Apprentice Geezer
...Ahhh... tracklocks, know them well... never had a clutch plate break though (sorry for your bad luck).
People, especially four wheelers, need to remember that this sort of equipment is meant to go get groceries or deliver mail (yes, they come in mail Jeeps and trucks and have a proven reliable history) on the street and gravel roads. they were never designed for a true off road, even moderate core, use. For that Detroit lockers have been around almost since God made rocks for us to crawl on. Selectable lockers, were invented later to make up for some automatic locker shortcomings...although they have their own.

What I would really like to see is a selectable ratcheting locker. i.e. an ARB (proven strength and reliability) Detroit Locker (proven strength and reliability) that can be switched off; it would eliminate the lack of steering a locked axle exhibits and allow safe operation in the slippery while allowing the front axle to steer well without having to switch the locker on and off, but still retain that option for icy road use.

BTW, I hear some concern about air locker reliability; in the last 30 years I have seen exactly one frozen line; on a vehicle whose owner refused even to grease his U-joints (lack of maintenance, not my vehicle) and since ARB changed the fittings like 15-20 years ago all leaking hose issues have gone away... the internal O rings on my oldest one (on the order of 25 years, might be older, I'd have to count) even still seal well and it is in its 3rd vehicle.

Since I am getting ever more antique and have been able to ease back on the adrenalin; I don't need lockers for, rocks, mud, the street, interstate, snow on roads or to go to the mall; and living where it snows find automatic lockers to occasionally be a hazard when on the street.. so for me and thousands of others a relatively heavy duty (in case I decide to do some of the more difficult moderate trails) limited slip will work just fine... If I need to do some adrenalin/a very difficult/moderately extreme trail (body damage likely to certain) I'll use the Jeep (ARB and Detroit equipped).

Most vehicles with 4wd never leave the street (Yea!, more, better parts for me!).
Of those that go off road most never see many, if any obstacles that actually require a locker, IMO.
Lockers do make off road driving significantly easier because they reduce the needed tire quality, suspension, and skill levels (and can hide a multitude of sins) IMO.
I found that after I got lockers my need for a winch went to near zero (my friends still need my winch though).

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