yes have had a truck with the Eaton in it. Did not care for the street manners, also drive higher speed highway. I drive about 40k a year and 1k of that is true off road on our ranch in NM and it Texas. Everything from very loose fine sand to mud and loose rocks. In the fine sand and mud (when it rains it is high desert in NM) a locker "controllable" is much preferred because the limited slip is not much help. Hope this clears this up for you.

 

I concur with this, and your aforementioned detailed description. Allow me to expand a bit. If one does not understand the concept of torque bias, you'll be lost in this topic. I would recommend getting a book by Jim Allen; Google it. He's written a very detailed book on diff operation and has tons of examples and details about the nuance of axles by all the major OEMs for the last several decades. ... Not 100% comprehensive, but a great place to start your learning about axles and diffs.

It's my intent to compliment C12H24's description a bit more in detail. But his concept of torque bias is completely correct. Bias is often and correctly expressed in a "ratio" referring to the multiplication effect of torque available, transferred relative to disparity between axles. The higher the bias, the greater the ability to transfer torque from one side to another. If the diff has a bias of 2:1, it can only transfer 2x the torque to the side with greater traction. If the bias is 5:1, it can supply 5x the torque of the slipping side. The concept is based upon the amount of available torque that can be sustained at the lowest point of traction (the side that has the slipping tire). The slip is measure as a "thrust" at the surface (force in pounds), but once converted to rotational energy at the axle it is "work" (force x distance; torque in ft-lbs). This has nothing to do with torque from your engine; this is about how much force the lowest-grip wheel can sustain. If you have a tire that can only provide 100 lbs of thrust force, and your bias is 4:1, then the tire with good traction will get 400 lbs of thrust force via the differential traction device. This is a description of the amount of torque re-balance at a max limit; a 3:1 unit will provide up to 3x the bias but start to slip internally after that point. But that varies with the traction conditions. Examples ....
- if you have a 4:1 device, and you're in sand, you may be able to get 100 lbs of thrust from the inside slipping wheel in a turn, and then you can have 400 lbs on the outside wheel via the diff traction device
- if you have that same 4:1 device, and you're on ice, you might be able to get only 25 lbs of thrust from the inside slipping wheel, which means the outside only gets 100 lbs of drive force
The point is that the bias is a ratio of the max available force at road surface, one side relative to the other, which is achieved via a traction control unit in the differential. Bias is a ratio, not a direct measure of magnitude that is static in all situations. Bias is considered as the ratio of better traction to lower traction, but is viewed from the low-traction side.

There are many forms of traction enhancement tools for the diffs.
- Spool: effect of a straight axle from end to end; absolutely no diff effect and output 100% equal to each side at all time (technically infinite bias because there is no disparity as the tire with greater grip will be the controlling factor for thrust force). Great for drag racing and sled pulling; horrible for real world use.
- "Lockers": A super-broad term that gets over used and misunderstood. Anything that "locks" in my definition effectively becomes a spool-type device; truly "locks" one axle to another, with no intent of shifting any bias. The only way this alters or "relieves" is when something breaks. Great for off-road and slippery conditions in slow speed applications; very bad in high-speed circumstances because it can and will cause the rear to step-out once both tires loose traction at the same time. Ford now offers an electronic locker; this mechanically locks one axle to another via electronic activation. Air-lockers achieve the same task pneumatically instead of electrically. GM has for years offered their "Gov-locker" (aka gov-bomb; for their propensity to explode the carrier in sudden high-torque bias changes, but I digress ....). The G-80 "Gov Lock" that GM offers is an Eaton product, and it is actually a limited-slip clutch device. It works in LSD mode in low-bias all the time; the clutches are always engaged just with any other traditional clutch LSD. However, it has a complicated inertial rpm-governed engagement system that operates a pawl to engage a cam-ramp that further forces the clutch pack together with more clamp force, thereby "locking" the axles by providing more bias across to the other side. I disagree that this is a true "locker", because it is merely altering the bias effect via more clamp force on clutch pack. We could achieve the same effect if stronger springs were placed inside the carrier and eliminate the clamp ramp. However, the "effect" is that the axles are "locked". This is a matter of perspective and an argument of words between different camps. In theory, if enough torque bias were present and enough traction were present, the clutches would still "slip" (or something would break) even when "locked". Essentially think of the G-80 as a variable bias device; light-bias when low rpm delta exists across the differential, until a disparity enacts the clamping system and it becomes a high-bias device. (Hence- these often shatter the carrier in off-road high-torque applications, like mudding in your tuned Dmax diesel with 44" tires ... as just one example). A different type is a "Detroit Locker", but it uses relief system using springs and dogs. Very robust, very reliable. But does not allow for light-bias to exist in low traction applications; snowy roads will induce the effect of full lock because not enough force will be available to induce the system to unlock, and so it acts as if a spool in wet/slippery conditions and can cause a step-out at times you'd not expect it. Essentially a Detroit Locker is "locked" until a force overcomes the spring/dogs. A G-80 "locker" is only LSD until a condition causes it to "lock", which is really only causing more clutch friction and not truly "locking". True mechanical lockers are not sensitive to lubes, whereas the G-80 most certainly is because it is clutch driven.
- LSD (limited slip diffs): basically a broad term for units that do allow bias and can often be "tuned" for the amount of force application, but the "tune" (bias ratio) is set and changed only with modification of the unit. These can be systems like clutch-driven units (Ford's Traction Lok, for example). The only way to alter the bias is to use different springs and/or clutch materials; but they can be "tuned" for desired bias. They will act with a bit better street manners, but will not provide good traction off-road if the bias is set low. Clutch systems also suffer from wear-out; they will lose bias slowly from day one of service; they never get better and only lose bias balance with age. Clutch LSDs are very inexpensive to make and repair, so they have a strong following; they are rebuild-able when worn out. Other types of LSDs are things like cone-clutch units and pinion-type units (Torsion is a brand name that is an example). These work well because they don't really wear out. But they cannot be tuned by the consumer as the bias is set at the design phase (clearances, ramp angles, pinion angles, etc by the engineers that develop them). Most all LSDs are sensitive to some varying degree to the lube properties and additives. Pinion-driven LSD are some of my favorites because they are super simple, don't require driver inputs to activate, and are very robust and long-lasting if sized properly. But they ain't cheap!

Just like lubricants, guns, stereo speaker, and girlfriends, there is no "perfect" answer. Each system will have it's pluses and minuses; each a niche they do very well at and those were they suffer. I, for one, like the electronic locker system; it suits my needs and I'm aware of how/why/when to use it. Those that want a "set and forget" system would be better off with some type of LSD. However, with most OEMs, you don't get choices past one option for traction control. Ram only has LSD if I understand it now. GM only offers the Gov-locker. Ford only has the E-locker. The only way to get something different other than what they offer is to go aftermarket.

 

The locker works but only when going at a slow crawl, which makes it kind of worthless.. I thought I was going to love it and use it all the time out in the fields just like in the semi's however the fact that it shuts off at 20mph makes it worthless. It doesn't take much wheel-spin to get to the 20MPH limit so when you actually need it it is not available
Its another thing that Ford engineering had a good thought on yet missed just one of the fine details making it worthless.. I have 6 cameras on my truck that turn off at 5mph yet I can open my tailgate at 75!!!

 

There is a plug in that disables the 20 mph limit. So when you get wheel spin it doesnt cut out. It takes about 10 minutes to install in the passenger side kick panel.

 

I have used mine many times in sand/mud/lose rocks. It is FAR from useless and with the Right Driver than knows how to use it, is outstanding.
I drive on my own property where the goal is to get where I need to go while causing the least amount of damage to my surface as possible. Many folks like to just see what they can tear up in a muddy field but that is not for me because I have to deal with the erosion or fixing the ruts with the plows later on. Sometimes damage to the surface is unavoidable and I understand that as well. On two different occasions however have had to evict oil field workers who we tearing across the field next to a unpaved road just for fun. My SUA's are written to allow me to do that fwiw to others who may be in the situation I am in with the oil field folks.

 

I had a limited slip in my dually because that is all that was offered. It worked better than expected. I prefer the locker. To buy a selectable, electric locker like Ford is offering would be expensive. The asking price is very fair. They are not as convenient as a limited slip because they are not automatic, do not engage or disengage instantly, and cause a problem with turning. But the limited slip has a "limited lifespan" and also only transfers torque up to a certain amount and up to a certain speed. GM's G80 Eaton autolocker in some ways is better...it fully locks and is automatic and quick responding...but is not as durable and requires wheelspin for it to engage. The factory autolocker on my 2005 GMC dump truck still works fine. But some blow up with hard use.

 

I am very interested in this.. do you have any additional information?

 

When I'm driving across my own fields and need the momentum/speed to make it up a hill, I would much rather have the traction from 2 wheels than the 1 wheel spinning

 

The locker drops out at 25mph in 2WD or 4x4 High...it re-engages at 20mph. I would suggest even on a field 25mph is pretty fast and probably sufficient speed for momentum. If that is not enough, use 4x4 Low. In this mode, the locker will not disengage until 62mph and will re-engage at 56mph.

 

This is why I own 4 WD vehicles only.

 

Me too, just saying I thought that the locking diff would be real cool and that I would use it more than I would 4x4, turns out that is not the case

 

Got it. Yes I use the 4wd most of the time just to keep from spinning the rear tires...……….

 

WOW - thanks all for responding. Its been quite an education. The 30 minute video was very good although it covered far more than what I was seeking. I learned a lot, and again thanks for your time and expertise.
Bill

 

I thought there was a thread on this, but cannot seem to find it.

 

Yes i made a thread about it a while back on here. SPE Diesel sells a kit to over ride the 20mph. It works great i have it installed. Only downside is it removes the locked indicator so you have to remember to disengage it when you dont need it. I used it the other day to get my 42ft camper out of the grass field that the iowa state fair uses for camping spots. They got like 2 plus inches of rain and it was soup. Well worth the $50 to me.