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& Experiences with Lockers
by Stu Olson
There has been, and will always be, several hotly debated topics in the off-road world. One of these topics is the ever popular locker.
What is a locker? It is short for locking differential. The differential is that big "bulge" in the middle of your axle that allows the left and right axles to differentiate while you go around a corner. Normally, one slows down while the other speeds up. If you just had a solid axle connecting the left and right sides together, turning the corner would be much more difficult than you can imagine. Since both tires would be forced to travel at the same speed, and neither of them likes this, they would drag and slide their way around the corner and make for some very undesired driving indeed.
A regular open diff keeps the average RPM of both axles constant relative to the drive shaft rpm. In an open diff, with one wheel experiencing a complete loss of traction (0 RPM), the other wheel will be turning at twice the RPM that it would be if both wheels were at the same rpm - relative to the drive shaft. This happens because of the spider gears. This same differential characteristic carries over to the limited slip design (LSD) which uses the spider gears. So, when an open diff is going through a turn, and good traction is available (asphalt road), the outside wheel turns faster and the inside wheel turns slower than if both were going in a straight line with a constant vehicle speed.
In an automatic locker design, which does not use spider gears, at least one wheel must turn the same (relative) rpm as the drive shaft while the other wheel can turn faster (but not slower). In most all automatic locker designs, the inboard wheel drives at the same (relative) RPM as the drive shaft and the outboard wheel unlocks and travels at the increased ground speed which is what is driving it.
Early in 2000, I decided it was time to upgrade my TJ's drive train. I was going to make a Death Valley run in March and the spend a week in Moab in late April. My factory Dana 35c rear axle, with the limited slip diff, was not going to give me the performance I would be requiring. After a lot of reading and discussions with good friends, I decided on a new Dana 44 rear axle with 4.56 gears and a Detroit Locker (the Dana 30 front got a new Detroit TrueTrac).
Actually, the decision as to what kind of locker to get was not actually made until the work order was being filled out at the 4x4 shop. I had narrowed it down to either the Detroit or an ARB. I couldn't make up my mind. Both are great lockers....but which one should I get? Money wasn't the main driving force since I already had a QuickAir 2 installed in the TJ. With that out of the way, it was only a couple of hundred dollars difference between the cost of the two lockers. Considering everything that I was having done (I was getting new BFG MTs and new alloy rims too), this was less than the tax I was going to be paying.
As I stood at the counter, making comments on what I wanted included in the work order, we got to the locker. I said, "Why don't you figure up the price of an ARB and one for the Detroit and I'll see which one looks better." Little did the guy know I was still struggling with which locker to get. He started on the ARB first...."let me see....one locker, one spare solenoid, a spare fuse....". "Wait a minute", I said. "What's with all of this spare parts stuff? I asked you for an ARB price workup, not your spare parts inventory."
The guy at the counter, with a little smirk on his face, looked up at me and said "Do you actually plan on going off-road without spare parts for your ARB?" That was it....my mind was made up. Probably not the most scientific way of doing it, but I thought it beat the heck out of tossing a coin. I will admit that good 'ol Murphy (the guy in Murphy's Law) does seem to follow Jeepers around on the trail. I figured that the less parts I have to make my locker work, the better off I would be.
Now...before someone decides to flame me about what I just said, let me say that I have nothing against ARBs. (Some of my best friends have them!) I just said I struggled with trying to decide which one to get, right? Would I use one in my Jeep? Well, if I were going to buy a Jeep, and it happened to have an ARB locker in it, I sure wouldn't let that influence me either way.
Before I had gotten my drive train upgraded, I drove out to a particularly nasty trail that I heard was going to have some good use that day. I took a friend along. He was new to the off-road world and wanted to see some "carnage". (One guy managed to roll that day.) We were watching a well built up Cherokee (might have been a Grand, don't remember) working a very difficult section of the trail. He was on very uneven bedrock, trying to make a tight up-hill turn, and also making a great attempt at keeping his rocker panels looking more or less new. It became apparent that he was struggling more than he should have been. He was locked, front and rear, with ARBs. After a bit of "detective" work, it was determined that his rear was not locking. With just the front locker working now, and the rear axle running in the open diff mode, he finally made it up to a flat spot where he could get off the trail a bit to check out the problem. After about 30 minutes they found that the solenoid was leaking. They did a trail fix on it (not sure what it was....has something to do with jamming a screw in some place) and he got back into the action.
My Moab trip paired me up with a CJ and two YJs that were running ARBs. I ran with all but one of these Jeeps for 5 of the 7 days I was wheelin' there. Both of the YJs experienced air leaks but managed to get them fixed with only about 30 minutes of effort. The CJ kept going, but his compressor was sounding pretty bad. We got to talking about it and I discovered that this was his 3rd ARB compressor (the previous two replaced under warrantee). He was not happy with the compressor and we talked about my QA2 for a while.
OK....so granted, this is also not scientific evidence that shows that ARBs are bad lockers. It is evidence that Murphy's Law does follow Jeepers around and makes life interesting for us. In both of the above situations (the nasty trail and Moab), many of the participants were using Detroits. In the case of the Moab trip, everyone not running an ARB was running a Detroit (OK....so we now know which lockers are the most popular, right?). Again, all I am saying is that with all other factors being equal, I personally will (and did) opt for the Detroit Locker because of the reliability factor....it is just plain less prone to failure because the of the reduced number of supporting parts.
I have talked with ARB guys on the trail who have had their lockers in for 3 years and have never suffered a failure of any kind. Most ARB owners usually blame poor installation practices for the problems that you hear about. I am sure there is something to this. Again, it goes back to Murphy's Law....the more things there can go wrong, will go wrong. If you have a reputable shop do the install, and they do lots of ARB installs, and the folks who have had them done there say they do good work, you should come out with a quality install and not be bothered with failures resulting from bad mechanic practices.
The ARB Air Locker is a driver-controlled differential lock actuated by pushing a dash-mounted button. In a tenth of a second, compressed air actuates a piston inside the differential which engages a locking gear, instantly locking the differential and directing driving torque to the wheels with maximum traction. The diff lock is simply disengaged by again pushing the button. The Air Lockers lock the axles together, providing 100% traction to all wheels, allowing you to safely traverse even the most difficult terrain.
The ARB requires an air source between 85~100 psi. The air source must be controlled, either via manually operated valves (I have a friend who did this and says he finds it more reliable) or through an electrically actuated air solenoid. The later is known to fail upon occasion....fact, not myth. If you have a spare and some tools, it should not be a big deal to put in a new one.
The ARB locker costs around $150~ $200 more per axle than does the Detroit Locker. In addition to this, you will need some kind of an air system to operate it, along with the appropriate control switches, air solenoids, and air line, etc. This will add several hundred $$ to the overall project cost. If you already have an air supply in your vehicle, you can use it along with a pressure regulator and the necessary switches, lines, solenoids, etc. This will help reduce the cost.
Tractech makes several locking differentials, the most popular being the Detroit Locker® brand. They keep the wheels locked together (except when turning) so that together the left and right wheels always deliver maximum traction to the ground; neither wheel can spin out. They allow different wheel speeds in a turn by disconnecting the faster - moving wheel (usually the outside wheel which is ground - driven faster throughout the turn) and driving the vehicle with the other (inside) wheel. After installation, there is no special maintenance required. Follow your vehicle's maintenance schedule for periodic differential fluid changes and you are all set.
This past week at Moab (April 22, 2001), we had a chance to observe just how much weight transfer occurs on a TJ when going up an obstacle and the result of such on vehicle performance. Many drivers may not be aware of how much such a weight transfer can affect their vehicle.
Josh (aka., Shlingdawg) blew a rear u-joint while attempting to climb up onto a slickrock fin. At that point, we were about 1/2 mile from the end of the trail with about 3 fins to go.
We were going to winch him up the first fin (the one is u-joint blew on). He had just tried to drive up the fin with only front wheel drive (the rear drive shaft was removed) and made it about 10' before his open diff starting slipping the front tires. His tires were howling on the slickrock as they fought for traction.
It was suggested that he turn around and try backing up. Now, remember that it is still the same open diff, but this time it now has weight on it (unlike when he was driving forward).
I stood there and watched him back to the top of the slickrock fin without once spinning a tire. A good solid 75' climb with perfect traction. Yet, when attempting to drive forward, the tires were spinning helplessly within the first 10 feet.
Anyone that wants to tell me that front lockers will "dig right in and give you all the needed traction" is wasting their breath on me. My first locker went into my rear axle and I have never resented it. I have the luxury of driving moderate trails in 2WD and still enjoying the traction advantage provided by the Detroit while having highway style handling on the front end.
My basic question is "Why put your only locker in the axle that will often times have so little weight on it that it can not provide any useful traction?"
Granted, there is a lot of weight on the front axle when you are coming down off of the obstacle, but I have rarely found the need for a locker at that time. I always seem to need one when I am climbing up onto it.
I've always believed in locking the rear axle first and Josh's performance on the slickrock fin was just more proof that typical weight transfer can render the front axle virtually useless for traction.
Comments I've read on web forums and e-mail.
I just copy and paste these into this section. I look for both Detroit Locker and ARB comments. You be the judge. A search of the web for "locking differentials" came up with lots of links to e-mail and forum postings. Here are a few that I copied:
".... PROBLEMS WITH ARB COULD BE BAD O-RINGS . I HAVE HAD 5 LOCKERS LEAK DUE TO O-RINGS. ARE YOUR O-RINGS BROWN? IF NOT CONTACT ARB."
"....ARB's are great, but if your compressor goes out you're screwed (Cbassett's went out on the Rubicon trip this week) and he was left without a front locker. I've yet to hear about a Detroit failing."
".....I've had a leaky o-ring, a broken air-line, and a
leaky solenoid so far. When it works, it is a great locker."
(note: he was describing his ARB)
"....People make out full lockers to be some sort of evil handling demon that will throw your truck off a cliff at the first opportunity. I've had mine in for about 30,000 miles now, and other than an occasional "Ka-POW!" sound (usually while backing up) and increased axle wrap before I put on the torque bar (now slight wheelslip - mini burner - on polished concrete or slick asphalt at low speeds), the thing is transparent. I wouldn't even know it was there, except I almost never use 4 wheel now. It's been to Tahoe, Oregon, Mexico, Arizona, Nevada, etc., and no problems, nothing unusual. So full lockers are not the Devil's own street-handling device in my case."
"....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!"
"....If there is no air pressure applied, heavy duty springs unlock the arb. So if you are staying locked either there is still air pressure to it or something in the arb itself is busted and will need to open pumkin. Look for broken parts when you pop the cover. I have the ARB paperwork in front of me and it really doesn't address your problem."
"....This could be caused by a solenoid valve not opening and venting the air when turned off, or not closing and stopping the air from going to the locker."
".....I'm going to back off of my staunch defense of the convenient ARB locker. Many JUers mentioned ARB's unreliability, while I had no problems for a close to a year while visiting Moab seven times during that period and trying most of the nearby Denver trails. The rear had to be replaced and the compressor was rebuilt in May. The compressor then had to be replaced in July. Now the rear locker would not disengage because of a broken part. Although the ARB reps are terrific in their follow up, their warranty is worthless. I was e-told that the warranty would have covered the broken part and labor if the unit would have been shipped to them. Now tell me, who is going to take the time to crate the unit, send it to ARB for their inspection, be without the use of the Jeep while waiting for a reply."
"ok guys...I just got my stainless steel arb line from
I have tried calling them, but no one is answering...
The problem is that I have the line, but none of its fittings will attach to the nipple that comes out of the top of the diff from the arb itself.
What do I do? Am I doing something wrong here?
I went to home depot and sears to try and find an adapter, but to no avail.
Any help would be greatly appreciated!
You have to return them and get the correct ones. The fitting sticking out of the diff is metric and uses metric sized line. It gets worse, part of the valve sizes are British pipe on one end and American pipe on the other (NPT)."
"My front arb stopped working, compressor kept running, no lock up. Got in touch w/arb usa and they sent me some o-rings, opened up punkin found 6 bolts and their broken off heads (7mm or 9/32" by 11/2") washers and some type of T-washer attached, and 2 pins broken in half. The teeth on ring gear the ones I can see with out removing locker appear ok any ideas what broke, and is this a simple fix, was the locker installed wrong was locktite supose to be used and maybe wasn't. Guess I should check the back ,dreading that."
"I had ARBs in my stock Dana 30 and Dana 35 for about 4 years. And I now have ARBs in my Dana 60s front and rear. I have had a lot of trouble with ARBs! First, the compressor. I think a cigarette lighter plug-in compressor would be more reliable. It's crap. Plain and simple. Went thru 3 of them.
The Dana 35 locker grenaded on me twice. This was the RD59 model I had the trouble with. The cross-shaft was smaller than stock and I busted it twice. ARB paid the whole bill the first time for the new locker, ring & pinion and labor. The second time, they sent me the new RD69 model with the new larger cross shaft and I had to pay labor."
"Well I for one did not enjoying ripping on something I spent over $2,000 to get parts and install. I used to sound like many of you on the list, thinking ARB's were the greatest thing, other's complained because they were jealous, and people were just mad that they didn't get them the first time. Well, my ARB's turned on me, and I for one would never recommend anyone get these. I have talked to numerous people having problems w/ ARB's, and this list is the first place I have even heard of people having ARB's for several years w/o problems, usually it seemed that anyone I had spoked too that had run them for any amount of time had problems w/ them. Oh well, the bolts that hold the carrier together sheared off my ARB, *under street use*, after 3 months of owning them (hadn't even gotten a good chance to really use them), got caught in my ring and pinion, and there goes my rear end. Then, I got stuck w/ a 3 week turnaround to get this warranteed and repaired on what was my daily driver, so I basically sat home for this time. In the end ARB ruled that it was properly installed, and their fault, and yes it was a Dana 35 model, but this was a little over a year ago, and I have heard of 10 or more people now who have had this happen in Cherokee's. Oh, after this was fixed, I made it about 3 weeks before the solenoid on the compressor went out, not a big deal to replace, but sort of a joke."
"I guess if you don't have the Dana 30 front or 44 rear you may justify it, but ARB's are junk in my opinion. I have heard of Detroit's breaking far less often too. I can only imagine how fun it would have been if my ARB had gone out in the middle of a trail where you need lockers at both ends, and I being left w/o even rear wheels to turn. Not something I could fix, I know that for sure, so I won't mess with them again. I guess if you could set up a ring and pinion, and new locker on the trail though, go for it!!"
"OK, I know I'm not the first one that this has happened to. But I noticed that my Jeep was driving funny after a day of wheelin'. When I suspected that the rear ARB was frozen-up, I raised the rear axle & placed it on stands & attempted to spin the tires to see if they rotated in opposite directions as they are suppose to when unlocked. To my dismay, they spin in sequence all the time. I started my ARB compressor, & tried to see if air was bleeding according to design by turning the diff control buttons on & off several times. It seems to be bleeding normally. I also swapped the front & rear electrical solenoid switches that are mounted on the compressor. But had negative results. Does anyone have any suggestions of how to "free-up" the suspected ARB from it's frozen position?"
"They showed me that if they played with the switches (the dash & switches were all torn apart), that they could intermittently get the rear to lock & unlock. It was true. However, sometimes the front wouldn't lock even though the rear was locked. The Jeep was up on a hoist, so we could spin the wheels and watch what would happen as the lockers were being engaged & disengaged. They told me that they were pretty certain that it was electrical/solenoid/harness related problems at this point. But haven't narrowed it down yet to the cause. Well today I went there on my way home. They "narrowed" it down to six components that they say need to be replaced! Grand total for labor and parts w/tax $248.62. I was kind of relieved that the lockers themselves seem to be OK (still to be determined once all put back together)."
"I noticed a air leak coming from my ARB solenoids, only when they were activated. I figure out it was coming from the front solenoid in the center of the shaft. It is threaded so I found the correct screw, wrapped some teflon tape on it and then tightened it up. I am just wondering why it would be leaking from there? Am I going to mess anything up by plugging it? Is there suppose to be something in there to begin with? Because, the other one doesn't have anything in there and it's fine. Does this have to do with the compressor heating up, a few weeks ago (since it is screwed to a tee in the compressor)?""Does anybody know if an auto parts store carrys regular pressure cutoff switches? I can't wait for arb to send one out. POS switch wouldn't cut the air compressor off. I hope I didn't blow out my O-rings. 3 weeks old."
"Just a simple story of how the ARB can surprisingly go to shit. I had been out wheeling and got into a predicament where I had to back up rather aggressively. Well I managed to really dork up my exhaust. I had to cut it off behind the muffler as it was un-repairable...no biggie. Well the exhaust was then blowing straight back to where the hose entered the diff. It heated the line enough to allow it to burst when the locker was engaged. No more locker."
"It started with finding a suction pump at Pep-boys. With this pump I was able to suck the diff. oil out without removing the covers. The rear diff. was a breeze, but when I got to the front, the air line (copper tubing) was in the way of the suction pump hose. Now, like an idiot, I moved the tubing about 1/4 inch, moved real easy. Everything appeared normal and I went wheeling this past weekend. I noticed when I released the air, from the front ARB, the normal psssst sound of releasing air was muffled. When we got back to camp and looked, there was oil in the front air line and diff. oil had been squirting out the front solenoid. I realize now that moving that front copper line caused an air leak inside the diff. I am planning on replacing the tubing this weekend and would appreciate any advice from those of you that are more familiar with this system than me."
"ARBs were working just fine, now I can't get the air to discharge or maybe the compressor to come on. I am leaning toward the compressor not coming on due to that I am not currently locked. Anyone had this problem. Going wheelin this weekend, must have lockers.... help."
"back when i had arb's, the most common problem was the fuse. It went out a lot. they also have an interlock with the front locker and the rear locker. the front will not lock unless the back is already locked. You might want to check to see if this interlock is working. there is also a pressure switch. The unit shuts off once there is enough pressure in the line. If you have an electrical problem to the air solinoid, then the compressor will fill up the one time, then not do anything until the air is released. if the solinoid does not open to let the air out, the air compressor will not turn on, and it will seem like the compressor is not workingm but it is actually the solinoid. You can check this by just letting some air out at the compressor and see if it will start. Of course, check the fuse first. Mine went out a lot."
"When I fire my ARB air locker, the air goes through the housing and out the vent tube. What is the problem here. Any help would be appreciated, want to know what to tell the shop. ARB part numbers would be helpful. Also anyone else who has had this problem, what did it cost to fix. A forum user replies with, "What's it in??? My dana 30 did the same thing after one use. I thought it was the O-rings, but I pulled it and they were fine. It was leaking from somewhere internal to the collar. I pulled it out and sent it back to Drivetrain Direct and they sent me a new one. The new one has given me no problems what so ever."
All that being said, I had a pair of ARBs installed on
January 21, 2001. Hey, I thought it was time to see what the other side of
the fence had to offer.
It has been a couple of weeks since the January install of my ARBs. I hooked up with a couple of Jeepin' buddies and we ran Lower and Upper Tax Collector on a Saturday AM so I could verify that all was working as expected. I am happy to announce that an ARB locker feels a lot like a Detroit locker when it is locked and climbing over the rocks. (DUH....what did you expect me to say?) Seriously, it did just fine and as I said, it does perform just like a Detroit....a locked axle is a locked axle. I was very happy with the D30 performance. Stepping up from a top quality Detroit Truetrac to an air locker makes a difference on the trail.
Am I happy with my ARBs? Sure I am. Was I happy with my Detroit
hardware? Yes I was. The handling behavior on the street is the
biggest difference between the two brands, which I knew long before installing
the ARBs. I know my install was done by a very competent tech so I am not
worrying about things falling apart because of him. Time will tell how
reliable my new setup remains. I expect years of good service from it, as
I did for those two years I got from my Detroit setup.
August 5, 2002
I've received a couple of e-mails lately that asked how the ARB lockers were doing. I am happy to say they are working just fine. No problems....no oil blowing out the solenoid (that means my o-rings are in good shape)....compressor leak down test is well above the minimum ARB suggests, etc.
So....maybe you are wondering about all of those comments further up the page? Why so many negative comments about ARB? As I said earlier, most ARB failures can be traced back to a poor install (or, having them in a D35 which is NOT a good idea, IMHO). I have no doubt that my install was done correctly. The tech has done hundreds of them for the shop he works for. I did some checking around the off-road community and this shop has a good reputation (which I also knew from my previous Detroit setup) and they don't spend time correcting his mistakes.
Now that I have an ARB, I pay more attention to other ARB equipped Jeeps and how there air lines are ran, etc. I've seen a few that were...hmmmm....well, let me say that I wouldn't have the person responsible for that install work on my TJ. It takes all kinds to make the world go around. If you plan on using ARBs, find a competent installer and enjoy the fruits of your investment.
January 1, 2003
I thought some of you might enjoy this photo....you probably haven't seen too many of them (I know I have not). I was wheelin' in Johnson Valley during Thanksgiving, 2002, with some good friends from California. While climbing a waterfall, my buddy snapped an axle shaft on his TJ's Ford 9" rear axle. The resultant release of energy, when the shaft let go, took out the ring and pinion gears and the Detroit Locker. The only notable component that survived was the other axle shaft. Here is a picture of the Detroit. OUCH!
February 1, 2005
This past December, I did the first maintenance on one of the ARBs (the rear locker) since I had them installed 4 years ago. (I guess I should clarify....the first maintenance other than the routine changing of the differential fluid.)
I had noticed some oil was being discharged from the vent port on the rear locker's solenoid. This is usually an indication of the locker o-rings needing replacement. Troy was nice enough to give me some time on one of the lifts and with some assistance from Grady, I replaced the o-rings.
During the last 4 years, I've heard and read a lot of comments from folks who use ARBs and also a lot of comments from folks who have never owned an ARB equipped vehicle but yet are somehow blessed with superior knowledge in regards to how bad ARBs actually are. The one thing I've found to be consistently true is that the VAST majority of all ARB issues can be traced back to an improper installation. It doesn't matter if a "good shop" did the install or not....what matters is the skill level and attention to details of the tech who put the locker in the diff. Likewise, I've seen air line routing that is an absolute joke....it could be used as a poster child for line routing that begs to be burned off on a hot exhaust pipe or snagged on rock or tree root.
Do ARBs require more maintenance than Detroits? I guess so.....you don't have to replace the o-rings in a Detroit. I see this need for maintenance as no different than replacing bushings in a RE control arm or the u-joints in a drive shaft. They are all wear items and will require replacement at some point in time.