The detroit locker is a conceptually clever device, but it has flaws. For one, they're not as strong as ARB air lockers. Another issue is the constant clicking sounds which take some getting used to.
Because of the ratchet mechanism, the torque is overwhelmingly supplied to the inner (slower moving) rear wheel in a turn and the ratchet lets the outside tire "freewheel" ahead, supplied with essentially no torque at all. If there is loss of traction at the inside wheel, it can still cut loose and spin up to the rate that the outside wheel is going before there is engagement. Once a tire is loose, there is some loss of traction.
I thought about detroit lockers for a bit... but I went with air lockers for true spooling.
I am not at ALL an ATRAC naysayer. I didn't get it in my FJ because I knew I'd be going with lockers in the front and rear, but I've seen this technology do what I thought could only be done with full locking differentials.
I still say that lockers are better... but not as much better as I had originally thought!!
Detriot's are the strongest and most dependable lockers on the market, they are known for the abuse they take. The only drawback is that you cannot turn them off. They are an acquired taste for a DD. I have used them extensively for over 20 years and choose them over ARBs, having special shifters put in my transfer case so I can unlock the fronts. It is not a matter of cost once you start to modify a t case to go with your selection of lockers, I hve seen ARBS go out numerous times more than a detroit, problem with a detroit is when the shaft goes it takes the ring gear with it, Detroits are the bomb.
I do think an ARB is a nice locker, but the detroit is the stronger one.
As far as Atrac goes, I honestly believe that we are now seeing the future, it will be less than 20 years before we see the end of Lockers and systems like Atrac taking over, it is just a matter of a few ears development and they will also lock when needed. They are so close now it is just a taste of what is to come.
Ok... I'm still not cool with this. The way my brain works, I can't put something down until it makes sense relative to the rest of the things in there that already fit together. I handled a Detroit that I did NOT put in, but it came *this close* to being part of my last truck.
The issue I'm having is this:
Suppose you're using the Detroit in the rear end and you get into some soft stuff. One wheel thats in thinner mud starts to spin. If the diff was "open", then all torque would be lost to the spinning wheel while the wheel on better ground would just sit there. The faster wheel is powered, but it's spinning. The slower (unmoving) wheel receives about zero torque... zippo... nada. However, my recollection is that the Detroit ratchet deal doesn't let the wheel that ISN'T TURNING WITH THE DRIVESHAFT go slower, (it *COULD* go faster - that would be "freewheeling"). How it works when one wheel would start spinning out in soft stuff is that the other half axle gets dragged along, going at a minimum of the same RPM as the live side. It immediately behaves as if it were LOCKED. If you drive out of that mud hole and the other rear wheel drops into soft stuff, then the same thing happens on the other side.
Isn't that about right? ... that's what I remember it was doing in my hands.
If you're describing that the wheel on the INSIDE of a turn sometimes slips, then it completely agrees with what I think I'm describing. The inside wheel is taking the most torque, and the outside wheel is actually ratcheting forward on the locker as the differential gears rotate. The outside wheel is therefore getting less torque. When the inside wheel breaks free, it can spin up to a rate equal to the outside wheel, at which point torque is equalized.
I've run the physics model in my head several times and I just can't make it do anything else!
Ok... I'm still not cool with this. The way my brain works, I can't put something down until it makes sense relative to the rest of the things in there that already fit together. I handled a Detroit that I did NOT put in, but it came *this close* to being part of my last truck.
The issue I'm having is this:
Suppose you're using the Detroit in the rear end and you get into some soft stuff. One wheel thats in thinner mud starts to spin. If the diff was "open", then all torque would be lost to the spinning wheel while the wheel on better ground would just sit there. The faster wheel is powered, but it's spinning. The slower (unmoving) wheel receives about zero torque... zippo... nada. However, my recollection is that the Detroit ratchet deal doesn't let the wheel that ISN'T TURNING WITH THE DRIVESHAFT go slower, (it *COULD* go faster - that would be "freewheeling"). How it works when one wheel would start spinning out in soft stuff is that the other half axle gets dragged along, going at a minimum of the same RPM as the live side. It immediately behaves as if it were LOCKED. If you drive out of that mud hole and the other rear wheel drops into soft stuff, then the same thing happens on the other side.
Isn't that about right? ... that's what I remember it was doing in my hands.
If you're describing that the wheel on the INSIDE of a turn sometimes slips, then it completely agrees with what I think I'm describing. The inside wheel is taking the most torque, and the outside wheel is actually ratcheting forward on the locker as the differential gears rotate. The outside wheel is therefore getting less torque. When the inside wheel breaks free, it can spin up to a rate equal to the outside wheel, at which point torque is equalized.
I've run the physics model in my head several times and I just can't make it do anything else!
Sometimes it sucks to be a nerd.
I need a beer.
A detroit works like this
on a surface with little shear, such as pavement, the locker is always locked until a major difference is going on wheel speed, due to the non slip surface it allows the outer dogs to release and the outer tire spins faster than the inner tire but loses all torque. once in a strait line the wheels will turn the same, locked together. On a high shear surface such as a dirt road the tires are going to turn the same speed, same as the ARB as the are effectively locked together. IN any strait line situation they will remain locked,
If you were to see a model of a detroit you would see how this works, it requires bind to break them loose. This is, along with the strength of the units, why they have such a Large following, not only off road but in heavy equiptment. The units are always on. The drawback to this is on road where they can be noisy and have a effect called torque steer, Torque steer is the vehicle wanting to go strait forward for 1.2 a second or so after torque is applied to the vehicle no matter how the wheels are turned, it is caused by the unit needing a small amount of time to release the outer tire.
Hey Guys no expert here but embarrased the hell outa myself today when I thought I wouldtake this little hill near my house to impress my neice on the FJ'S awesome offroad cap and Fricken hello made it about 10 then 15 maybe 20 up and the tires start spinning and I'm thinkin where's my atrack and all.............................go home scratchin my hairless schull before I realize.................GOSH do ya think 45 pounds of PSI in each could have had anything to do with this......... Would have been so awesome too.
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Hey Guys no expert here but embarrased the hell outa myself today when I thought I wouldtake this little hill near my house to impress my neice on the FJ'S awesome offroad cap and Fricken hello made it about 10 then 15 maybe 20 up and the tires start spinning and I'm thinkin where's my atrack and all.............................go home scratchin my hairless schull before I realize.................GOSH do ya think 45 pounds of PSI in each could have had anything to do with this......... Would have been so awesome too.
post of the thread, LOL that is funny, tell you what, it is the little things that get you embarrassed
A detroit works like this
on a surface with little shear, such as pavement, the locker is always locked until a major difference is going on wheel speed, due to the non slip surface it allows the outer dogs to release and the outer tire spins faster than the inner tire but loses all torque. once in a strait line the wheels will turn the same, locked together. On a high shear surface such as a dirt road the tires are going to turn the same speed, same as the ARB as the are effectively locked together. IN any strait line situation they will remain locked,
If you were to see a model of a detroit you would see how this works, it requires bind to break them loose. This is, along with the strength of the units, why they have such a Large following, not only off road but in heavy equiptment. The units are always on. The drawback to this is on road where they can be noisy and have a effect called torque steer, Torque steer is the vehicle wanting to go strait forward for 1.2 a second or so after torque is applied to the vehicle no matter how the wheels are turned, it is caused by the unit needing a small amount of time to release the outer tire.
Yes. This agrees with my recollection. The outside wheel is the one that breaks free and "freewheels".
KarlVP said I had it backwards.
My frontal lobes can now relax.
Not to open another can of worms, but isn't "torque steer" where you gun it and the torque of the engine imparts some turning because of differential delivery of torque to the right and left rear axle shafts?
Yes. This agrees with my recollection. The outside wheel is the one that breaks free and "freewheels".
KarlVP said I had it backwards.
My frontal lobes can now relax.
Not to open another can of worms, but isn't "torque steer" where you gun it and the torque of the engine imparts some turning because of differential delivery of torque to the right and left rear axle shafts?
in a normal diff, yes, but remember what a thing is called, with americans have no relationship to what it is . Just refer to politics and hollywood and you will agree with that.
anyway. what we call torque steer with a detroit is it
s tendency to go forward for a second, not turn, once the cogs release it works simular to a regular diff and and you steer acording to input.
Ok, my brain is throbbing again... let's think this through.
The principle involved is that the ratchet mechanism makes it so that IF torque is lost to a spinning wheel, it grabs the non spinning wheel along with it, using the one-way ratchet. The other wheel can't go SLOWER than the one that is torquing and spinning.
So, as you come around a short radius turn, where the outside wheel necessarily has to go FASTER, the inside wheel should end up with the lion's share of the torque and the outside wheel should relatively "freewheel", clicking the ratchet mechanism.
Right?
Where am I going wrong?
When you're on the gas with a Detroit....it acts like a spool. I think that may be what's throwing you off Jon. ***ETA*** Any true automatic locker will not allow either axle shaft to spin slower than ring gear speed. Maybe that'll help. ***
I agree with you Doc....the ARB is stronger than the Detroit....if an axle breaks. I've personally blown a few axles and have wheeled with all kinds of rigs breaking axles and the guys with Detroits (especially in smaller axles like D44s and 30s) will often times blow up the locker at the same time. In this regard, I'd actually prefer a lockright, ez locker or aussie in a new carrier over a Detroit for a front axle application since you are so much more likely to break the steering axle than a rear. Axle breaks with an Arb by comparison rarely take out the carrier.....look at the comp guys. They aren't only running ARB over Detroit for the ability to turn it off....it's also in part due to the strength of the carrier when an axle breaks. Same reason why Eaton's Elocker has been dissed for comp rigs over ARB....they don't handle the shock loading of an axle break as well. In the Detroit, the dog clutch inside the detroit often grenades when you lose an axle b/c they have 1/4 turn of slop built into the design and the Detroit is so good at transferring torque loads that it also transfers shock loads....which in turn busts the dog clutch and can even snap the other side's axle shaft on occassion.
Sean
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