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Old 02-07-2013, 10:57 AM   #127
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No.

First of all, as a practical matter, nearly all 4wd pickups and large SUVs are equipped with some sort of locking or limited-slip rear axle. So the 4wd is providing traction above and beyond that.

There have been all kinds of situations where my 4wd truck and burb were stuck in the snow, mud, or wet grass, G80 locking diff and all, until I engaged the front axle.
I'm not sure about the standard thing. I'd have to re-review GMs offerings, but in 2013, G80 became a free flow option in, I think, all situations. It was even removed as standard in the tow package and left to the customer to decide if they wanted it or not. There may still be some trim levels and suspension packages where it is part of an optional package, but there are a LOT of 4wd running around with no LS or locker. It shuld be looked at closely when shopping or ordering.

For GM it'll be on the SPID label as "G80".
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Old 02-07-2013, 10:58 AM   #128
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I did learn quite a bit from the differential discussion. However it is somewhat difficult to put it all in perspective, due to the seeming disagreement about what term means what to different participants. However, I will file it away for the next time I buy a 4WD vehicle and use it for a basis to research what is available.
Again, I've had both, they both help, and neither is perfect. Lockers help more than limited slip, but it's a marginal difference. Most of the time, if you're stuck enough to spin one wheel with a limited slip rear, you're also stuck enough to spin both wheels with a locker. The performance of limited-slip diffs tends to deteriorate over the years and miles as the clutches wear. G80s work until they explode into 100 pieces at which point you probably can't drive the truck until you overhaul the rear axle -- though in many cases they last the life of the truck without attention. Other lockers have different failure modes but share the property of consistent traction performance up until the point of failure.
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Old 02-07-2013, 11:11 AM   #129
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Again, I've had both, they both help, and neither is perfect. Lockers help more than limited slip, but it's a marginal difference. Most of the time, if you're stuck enough to spin one wheel with a limited slip rear, you're also stuck enough to spin both wheels with a locker. The performance of limited-slip diffs tends to deteriorate over the years and miles as the clutches wear. G80s work until they explode into 100 pieces at which point you probably can't drive the truck until you overhaul the rear axle -- though in many cases they last the life of the truck without attention. Other lockers have different failure modes but share the property of consistent traction performance up until the point of failure.
Again, we're close in agreement, but I think there is a big difference between LS and and lockers in a normal towing situation or boat ramp type of need. If we want to talk about solo off roading and solo deep snow, etc, I am closer to your opinion. But I think, as this is a towing forum, and most of us will never be hitched up in deep snow or off roading in mud while towing, (OK, some of you guys might!!!) I think it is important to keep my comments confined to the audience. If I were posting in an off-road forum, my conversation would be very different. I don't think a G80 is a whole lot better than LS in a HIGH PERFORMANCE off road situation, as opposed to a farmer crossing his fields and through the ditch, or a construction worker driving through the site at low speed.

The eLocker is probably better for high performance off-roading IF Ford didn't play with the calibrations and algorythums too much. I have no clue how robust it is in the shock loading department...which speaks to your "100 pieces" comment. Ford does prevent, and removes engagement at 50% throttle in 4hi and 2hi....presumably to prevent shock loading.
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Old 02-07-2013, 11:31 AM   #130
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My Suburban has the G80 "gov lock" diff. Dznf0g is absolutely correct -- this is a locking differential, not a limited slip one (I've had those too). The G80 diff has two modes of operation -- open and locked. When it's open, it's just like a garden variety non-locking diff with no torque bias at all. When it locks, it locks completely and there's no slip at all until the torque limit is reached as dznf0g describes.
The new generation of LSD(Locker) is actuated "exactly" the same way older LSD's were(Torque bias between axles) and when torque limit is reached it reverts back to a limited slip.(to avoid breakage)The difference is that there is not a clutch pack or spring pre-load there is a solid connection that locks the axles temporarily causing high stress conditions on driveline parts.LSD's do reach nearly 100% torque bias(both spin at same rate) in high torque conditions but it is gradual and forgiving depending on what type of LSD used.
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Old 02-07-2013, 11:39 AM   #131
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The new generation of LSD(Locker) is actuated "exactly" the same way older LSD's were(Torque bias between axles) and when torque limit is reached it reverts back to a limited slip.(to avoid breakage)The difference is that there is not a clutch pack or spring pre-load there is a solid connection that locks the axles temporarily causing high stress conditions on driveline parts.LSD's do reach nearly 100% torque bias(both spin at same rate) in high torque conditions but it is gradual and forgiving depending on what type of LSD used.
Could you give me a brand and model of that type of LSD? I'd like to read up on it. GM doesn't use truck LSDs and I am unfamiliar with what you describe. That is, however, different than a G80 or an eLocker.
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Old 02-07-2013, 11:57 AM   #132
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Locker

What happens in extreme conditions where traction is required above the 20 mph threshold of a "Locker"
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Old 02-07-2013, 12:12 PM   #133
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Again, speaking from a road use and towing perspective, traction control and stability control is better than any LS, or locker, in my professional opinion, once at speed. And actually I would choose AWD/TC/SC in that scenario over 4wd.

In an off road situation, you present the problem that OEMs have when building for the public at large. Thus my distinction between my position on this forum vs. an off road forum, for example.
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Old 02-07-2013, 12:49 PM   #134
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In an off road situation, you present the problem that OEMs have when building for the public at large. Thus my distinction between my position on this forum vs. an off road forum, for example.[/QUOTE]
35 mph up an icy road in the snow (which is possible in August at high elevations) is not IMO an off road situation.Slippage can occur at any speed you know.
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Old 02-07-2013, 12:56 PM   #135
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Originally Posted by Sylver Slypr View Post
In an off road situation, you present the problem that OEMs have when building for the public at large. Thus my distinction between my position on this forum vs. an off road forum, for example.
35 mph up an icy road in the snow (which is possible in August at high elevations) is not IMO an off road situation.Slippage can occur at any speed you know.[/QUOTE]


Yes, and electronic traction control with stability control and now electronic sway control all work very well in that situation. Limited slip (the kind which is always engaged) actually interferes with the second stage of traction control (the individual wheel ABS stage) as when applied to RR, for example, it affects LR as well. Kind of makes for a 3 channel system instead of 4 channel. An open diff at higher speeds (ON ROAD SLIPPERY CONDITIONS) is better with electronic aids. I also prefer AWD in this scenario, for its front/rear variable torque splitting capability. (But, alas, no low set in the t-case for low speed grunt work.)
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Old 02-07-2013, 01:48 PM   #136
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The True-trac LSD is an automatic full-time no maintainence Friction/Traction control device that is easier on drivetrain components in all conditions and superior to a part time high stress Locker that must disengage (to "open" status and re-engage to lock) to protect itself and the drivetrain from catastrophic failure.All the while it compromises traction while protecting itself in this situation and it still provides no traction aid above 20 mph.To each his own,intended use and personal preferences and needs are what should determine what system is optimal for an individual TV as the circumstances and conditions are different and can be addressed with many options. P.S. the electronic traction control could force the True-trac to act more like a locked rear by transferring torque faster and limiting slippage.
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Old 02-07-2013, 02:11 PM   #137
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What OEMs use True-trac? Your last statement is true, but here's what I found back in the early days of ETC. Back then we used more aggressive TC in low speed/high loads situations, just as you describe (came into play more with open diffs than G80). While effective in some situations as a "diff lock"...sort of, it could bog down to the point that so much brake was being applied that the truck just stopped. Momentum was lost, then you were kind of potentially screwed. But the big thing, was this system ate brake pads/shoes very quickly if the truck was in slippery low speed, high load conditions a lot. I think there might be one manufacturer out there that calls this a limited slip or locking rear axle (can't remember which) and claims less axle maintenance (true), but totally neglects the accelerated brake maintenance.
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Old 02-07-2013, 02:14 PM   #138
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Old 02-07-2013, 02:31 PM   #139
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Ok, I thought so, but wasn't sure enough to say. Here's the thing. This is a thread where the question is "I'm truck shopping for an AS TV...do I need 4wd" I have tried my darndest to stay on track with what's available off the lot to help someone make a decision on what's available 2wd/4wd from the factory. If the question was, "What can I do to modify my truck to get more traction?" then there are A BUNCH of aftermarket stuff we can talk about...much of it not suitable, or overkill, for AS towers. I don't want to hijack this thread to make it a truck forum mod thread.

I suppose if someone wants to start that kind of thread, that's ok, but they are probably better served on a truck forum. Not trying to lecture.....just trying to maintain decorum.
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Old 02-07-2013, 03:01 PM   #140
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I don't think adding the Eaton True-trac will void warranty,but it is considered "aftermarket" even though it is a major supplier to the big three.
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