BEST REAR DIFFERENTIAL FOR 4x2 OR 4x4?

[jage]

Originally Posted by Silver350

You keep referring to a scenario where one wheel is on ice and the other has traction, but what about when 2 wheels are on ice with a differential that won't easily unlock? You will be facing backwards and in the ditch before your passengers stop screaming. Or possibly have turned your van into an SUV, a Stupid Upside down Vehicle.

Implying that a locker is instant death on any kind of ice. Look, I can do the same with limited slip- If you're slightly stupid and hammer down, it's pretty easy to break traction with both wheels. The problem is ONLY when you break traction, because then you have no lateral control. It's easier to break traction for both tires with a locker, but frankly I've been on an open diff and my old G20 walk sideways, simply because the ice was such there was no traction in any direction.

In exactly the right conditions, will the vehicle go sideways? Yes. But you STILL have to break traction, and if you don't need throttle to break traction, you're in trouble regardless of what you've got. With open you can spin a tire and have the other track. Sidehill is the only real problem I've had with permanent lockers front and rear.

I don't know about the TrueTrac, but AdvanceTrac sounds like it would be hard to get out of some places unless you can turn it off- sometimes spinning is necessary.

But having a locker is not bad, it just takes some driver- which I agree is a recommendation against for most people out there in the world, but then again most of those people shouldn't have 4x4. Also, just because people own a shop doesn't give them a clue.

Frankly I enjoy the clink, clink, clink, pop of a locker. It's like a Diesel or Toyo road hum, perhaps an acquired taste but something I enjoyed.

I'm not saying anybody should get a locker, and I'm not doing anything but selectable on the van, but equating them to instant carnage or overwhelming problems is not fair.

[jage]

Somewhat relevant to my rant- can't handle your corvette throttle? Turn a dial, hammer down, and let the computer keep you from plastering fiberglass all over the highway...

http://www.youtube.com/watch?v=ckNA9wsk ... re=related

[Silver350]

Instant death is just slightly overstating my point. I asked a similar question over at ExPo and all agreed that living where icy roads are a real possibility and a Detroit Locker were not a good combination for a vehicle that gets used primarily on pavement.

[coyotearms]

Originally Posted by jage

Somewhat relevant to my rant- can't handle your corvette throttle? Turn a dial, hammer down, and let the computer keep you from plastering fiberglass all over the highway..

That video makes it clear how frustrating it seems to throw a bunch of money at the drive train of an SMB to make it do amazing things. Do ya' think dat computa' can be jammed unda' da dash of my rig? Just think, the same 0-60 times with your SMB in complete safety!

Originally Posted by Silver350

On the other hand, if you have Advance Trac, the [throttle] will cut as soon as one or both wheels start spinning.

Two questions. What do you mean by the throttle cutting as soon as ... wheels start spinning? Also, is Advance Trac the same as Detroit Truetrac (http://www.eaton.com/Eaton/ProductsS...ials/index.htm)?

My last thought goes back to what I am trying to glean from others experiences: The suspension/drivetrain place I have been talking to, keeps trying to convince me to just do a selectable true locker on the rear (for my 4x2 drive train) as the best of all worlds. But what that view does not seem to address is that when your flying down the highway and bad conditions get a little ahead of you, would you rather have that rear diff be free, LSD, Detroit TrueTrac or Detroit Locker? You cannot go back and redo that section of road with your selectable locker turned on if that would have been a better way to go---you got to deal with the problem the first time. 10k lbs is a lot of inertia to control going sideways. Oh, and think of your life partner or your 16 year old behind the wheel at that time of reckoning.

[Silver350]

Advance Trac is Ford's traction control. It works off the ABS sensors and cuts the throdle during spinning wheel situations. One can manually override it under 25 (?) MPH.

Improving motive traction with power at 2 or 4 wheels does nothing for braking and steering traction. Appropriate tires will do more for your safety than any mechanical device ever will. I think your shop is correct in recommending a selecable locker.

[jage]

Originally Posted by coyotearms

Oh, and think of your life partner or your 16 year old behind the wheel at that time of reckoning.

Flying down the interstate? Open or LSD. Which means de-selected locker is the same thing. And I'd bet TrueTrac is indistingushible (or a Spool for that matter). But seriously, do you think anything would prevent an accident in this case? For each about 1% that a locker would have prevented, open would have prevented 1%, and 98% == wreck no matter what.

Flying down the highway with a locker locked is no safer or less safe than open in my opinion: just like driving at highway speed with a 4x4 is no safer than 2x4, less so because a lot of these drivers feel invincible when brakes are really the deciding factor. There are no magical handling characteristics (or deficiencies) to any of these configurations.

It's slow speeds under acceleration that are dangerous and really make a difference danger wise, and slow speeds under inclement conditions that they really pay off. For what it's worth, in the spirit of the original question I'd be inclined to say TrueTrac based on Bones' experience would be your best bet:

1. no decisions
2. good handling regardless
3. less complex

[coyotearms]

Originally Posted by Silver350

Advance Trac is Ford's traction control. It works off the ABS sensors and cuts the throdle during spinning wheel situations. One can manually override it under 25 (?) MPH.

Got it. That clarification should be of help if there just happens to be anyone out there that knows less than I do about this stuff, and hangs up over differences between Ford Advance Trac with Detroit Truetrac---two very different things. . .

I have gotten to the point now, after all the great discussions here, where I feel comfortable deciding between TrueTrac and a selectable locker on the rear. Given my experience during many winters in the Pacific Northwest with LSD on a sedan, I am tending toward Truetrac, based on it being just a better limited slip setup. And simplicity/potential reliability of that setup compared to electronic and pneumatic lockers also sways me in the direction of Truetrac. If that doesn't get me where I want to go, here comes 4x4. Thanks all!

p.s. Given that I have an EB and 5700 lbs. on the rear axle and it was soooo clear at Overland Expo (see my first post on this thread) that the rig has a serious exit angle problem compared to entry angle, that I am going to have a leaf added + reshaping of the Ford springs to get the rear up and do nothing in the front at the same time the diff is taken care of. Then if I do go 4x4 I will put out the big bucks for a total Deaver redo in the rear if needed to match the changes in the front. Does that sound right for the poor boy on the block?

[louie]

TrueTrac vs. PowerTrax No Slip.Opinions? Is the PowerTrax really less noisy on the street? Do either one of these lockers send 100% of the power to both wheels when activated or are they just an enhanced version of a limited slip whereby it sends all the vehicle power to the wheel with the most traction? I know it's been discussed over and over, but I am still trying to get an understanding of the safety of a rear locker if it kicks on at high rates of speed.

I have learned much from this thread...

Louie

[jage]

Originally Posted by louie

but I am still trying to get an understanding of the safety of a rear locker if it kicks on at high rates of speed.

It doesn't kick on, a locker is always distributing 100% to both wheels but the mechanism allows for the wheels to turn externally at a different rate, namely a tight turn. Turning right on pavement the driver tire travels further, so the locker rolls or ratchets to allow the slower tire to not bind. Off pavement the slower tire will likely just slip on the terrain.

Thus turning right at an intersection you might get a clack-clack-clack-clack-clack, whereas turning left clack--clack--clack, because the radius of the left doesn't require as much adjustment between the tires. That's my experience with EZ-lockers on a Jeep, the principle is the same but the TrueTrac doesn't look like it makes noise. The point being it adjusts for external differences in the rate of each tire's travel.

Going straight, zip, zilch, nada, essentially nothing because bother tires are moving at the same speed and with no slip in the terrain, there is not enough difference to cause the locker to ratchet.

[coyotearms]

Originally Posted by louie

TrueTrac vs. PowerTrax No Slip.Opinions? Is the PowerTrax really less noisy on the street? Do either one of these lockers send 100% of the power to both wheels when activated or are they just an enhanced version of a limited slip whereby it sends all the vehicle power to the wheel with the most traction? ...I have learned much from this thread...

Since I started this thread, I keep trying to make it has helpful to everyone as possible (thanks!), and I think it's been pretty easy to separate pure opinion from actual experience (although I am not sure what jage actually has on his rig, even though I thoroughly respect all that he has said!). In my first post on this thread, I have two links to Eaton who appears to make just about every type of diff except pneumatically actuated selectable "full" lockers. PowerTrax appears to be a name associated with PowerTrax "Lock-Right" and "Traction Systems" (http://www.richmondgear.com/). I am not completely sure what the differences are, but it seems like the Lock-Right does what the Detroit Locker does, and the Traction Systems may do what the Detroit TrueTrac does. The Detroit Locker is a differential that is always locked unless one wheel is going at a different speed than the other, at which time it disengages (the clack-clack... that jage refers to). The TrueTrac is a differential that distributes torque to the wheel with more traction. I "believe" (sorry) I have read that it does this up to the limit of about 80% of total torque available, which is apparently more than LSD's do, but has no clutches to wear out so it behaves pretty much the same with age (or failure?!).

I think the above description of the Detroit Locker jives with what jage indicated regarding what he referred to as a locker:

Originally Posted by jage

It doesn't kick on, a locker is always distributing 100% to both wheels but the mechanism allows for the wheels to turn externally at a different rate, namely a tight turn.

And I interpret what he means by distributing 100% [of available torque] to both wheels when locked is best understood by visualizing each wheel prevented from doing anything else but turning at the same speed. So if one wheel has perfect traction and the other no traction, 100% of the torque goes to the "good" wheel. How else could they turn at the same speed?

This does not address which is better for what, but it does open myself up to getting wacked if I got something wrong---but hey that's what this thread is about!