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Comments
-juice
However, let's say both sides have traction but the bump (left) side offers 2x of the flat (right) side for a total of 3 units of traction. If you were locked, you would have to loose the 1x on the right (b/c wheel must slip). The bump side must also provide some torque to cause the slip, at most 1 unit (some comes from engine). Hence, instead of 3 units of traction, you can only use between 1 and 2.
Now, I am not arguing for not locking up, that it's a bad thing. I am just pointing out that they are not ideal. Their binary operation is what makes the inconvenient but they are the cat's meow when you need them.
I maintain that the traction you sacrifice with the locker is traction you didn't need anyway. So if it drags the opposite tire along and the left one doesn't lose any what was your NET loss....0.
I have seen guys in Jeeps with LS diffs in back. On Christmas day this year, on a trail in California I had to pull just such a vehicle free. He had solid footing on one side and the LS would not transfer enough power to move the Jeep. I went through first locked up with no problem, even if I drug a tire now and then. As long as you have control over your lockers there is no better traction device.
OOps I had to come back and address one more issue. You say that a locker can't increase traction, it can utilize what is there. Tell me, what increases traction, tires or road surface are the only possible answers.
-mike
If these AWD systems wait until wheel slip is detected you've lost it already. On pavement its probably OK but out in the rough you'd be stuck.
Question: aside from equiping your vehicle with ARB air lockers, what vehicle comes factory with locking diffs?
The final point about increasing traction ... I was just responding to your original post saying "... found locking diffs to do anything but increase traction ...".
Traction control systems are excellent for road situations. I doubt they will ever take hold in the off-road community. They simply are not the best solution. I have read that they are very prone to overheating the brakes under heavy off-road use. But for most they are better than a locker.
gluiz, you caught me, what I should have said was that lockers are the most effective way to maximize the available traction. This is not an on-road solution though. Using lockers on a snowy highway for exaple could prove disasterous. They would definately cause instability at speed. I have always found the fully open diffs to very effective in snow. Generally speaking one wheel "could" spin but the remaining three do not maintaining stability.
-mike
-juice
The real reason is that it would screw up the steering something fierce. Now we enter the world of liability. The lsd is not like a locker that you can select to operate, the lsd is always on call. For anything short of a hard core off roader this would be a bad idea. Even in a dedicated off-roader the locker is far better. From experience I can tell you any lock up in front is dangerous except at crawling speed.
-mike
-mike
When you get an LSD like bwh refers to on his Porsche, it has high preload. I have a sports car with a viscous LSD and you don't feel much at all. However, it I spin off the line, it will "lock" up right away.
For a front LSD, you need low preload or you get funny steering effects as bwh pointed out. Furthermore, you have to worry about braking while turning in which case you cannot have any dragging/bias to one side or the other. Even if you have no preload, most LSDs cannot tell the difference between engine braking and acceleration. Torsens are becomming more common that LSD b/c they can tell the difference.
And finally about the parking brake trick - this works b/c you are putting more torque into the diff. This means the dynamic lockup comes into play which means you have a higher lockup. Is it a domestic vehicle?
Drew
Host
Vans, SUVs, and Aftermarket & Accessories message boards
-mike
-mike
Comments Please: If only big buck SUVs (Land cruiser, G wagon, Hummer, etc) have locking diffs and LSD is only effective to various degrees, it sounds almost economical ($400 to $600?) and more effective to install a driver selectable axle lockup setup (like a ARB air locker) in the rear of a plain jane 4WD with open diffs (<$30,000) versus the $35,000 to $50,000 SUVs with LSD, traction control or other systems.
Keep in mind the diff would be locked only for deep snow, sand and other 'tow me out' situations.
So I guess I agree and disagree with that appraoch. In a Camel Trophy type situation in a Land Rover I would get the recovery tools first. If I had say a Toyota pick-up and used it in the Rockies I would travel in a group, have a strap and a good jack, and buy the locker.
The only other point I was trying to illustrate was that most folks do not have a Rover or a G-wagen. So adding an air locker to most regular 4x4s is a terrific enhancement, more so that on a Rover because its capabilities already exceed most 4x4s.
Naturally having it all, lockers and the winch, is the real ticket.
How much and is the unmounted method feasible.
Didn't have it with me when I got stuck. (poor planning) I will pack it in the truck.
This is a good line of discussion. It transcends whether you push a button or not to get 4WD and how much better LSDs are over open diffs. When the going gets tough, you either get out the winch or you engage the locking diffs (you still may need the winch).
From tincups post, it sounds like $1,000 to get the air locker and compressor installed (ouch!). Good winches are probably $500 right? I'll continue to mull this over.
The 'riding on the beach' topic also has some good discussion on when the going gets tough.
The manufacture said it was a Full-Time 4WD and this site said it was a Full-Time AWD. My Santa Fe have a 60% of torque in the "Front" and 40% of torque in the "Rear". What do you think about this 4WD or AWD suppose to be?
-juice
-mike
The definitions I've tended to use are:
AWD: 4 wheel drive without a transfer case. This also means no 4lo.
4wd: Has a transfer case.
If the TC includes a full time option, meaning it has some kind of a differential, then its "Full time 4wd".
If it doesn't, then its just "Part time 4wd".
The TC may include a reduction gear, in which case it has "4lo".
These are all IMHO of course.
If not, who cares? Certainly not you, because you don't have a choice.
If you have a choice, all you need to know is whether any mode of operation is not for dry pavement.
If you have lo-range, you have to have a button or switch or lever to activate it.
So don't get hung up on what's it is called. Just know when each mode of operation should be and shouldn't be used (if you have a choice).
This AWD and 4WD is alway confuse and hard to explain to people. If someone pass by and ask which A/4WD system on the following car is work better: Santa Fe, Tribute, RAV4, Highlander, Forester, and Escape. Then how do we have a good answer for them. What do you think and what system is the best?
What badge you put on it is as unimportant as what the different manufacturers marketing depts. call their AWD or 4WD systems. A name or badge never got someone out of a ditch.
The Forester, RAV4, and Sante Fe are full-time, engaged all the time. I would label it AWD.
The CR-V, MDX, and Escape are part-time. They are FWD until there is slippage. They engage automatically, but only on slippery surfaces. The Escape adds a manual engage button, but it's still not meant for dry conditions.
Sound right?
-juice