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Know on some 4wd vehicles you can drive in 4wd hi in the rain. Would a lsd keep the rodeo from binding in corners? Tested the 4wd on dry pavement and it felt like a posi unit or being in 4wd low when it was actually in 4wd hi.
 

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Yea, you shouldn't do that again. It's bad for your truck, and dangerous too.

The binding your talking about comes from the fact that there is no central differential, like in all-wheel-drive vehicles.

When you're in 4wd (doesn't matter high or low, all that is is a gearing change) both the front and rear diff are driven at the same speed through the transmission/transfer case. But when you go around sharp corners your front wheels actually need to travel farther, but since in 4wd they are locked to the same RPM as the rear this caused the binding your talking about. This is why if you read the owners manual in any 4wd vehicle it will tell you not to run 4wd on dry asphalt or any other high traction surfaces, it can lead to dangerous understeer, and damage driveline components too.

AWD vehicles (Subaru, Audi etc..) have a third differential between the front and rear drive shafts, which allows them to turn at different RPM, just like the diff in the middle of your axle let each side spin at different speeds so you can go around corners.

So no, a LSD has nothing to do with what you're talking about. All an LSD does is take some power from a wheel that is slipping and send it to the other side. So an LSD in really slippery road conditions can actually be hazardous if you're to heavy footed. With an open diff in the rear on snow packed, icy roads, when accelerating I can plant my foot in the skinny pedal and the side with the least traction will break traction, and the other side won't, and I'll just spin one wheel and nothing very exciting happens. With the LSD in my Rodeo, when I do that, the side with the least traction breaks loose, then only then a split second later the LSD kicks in and both sides break loose, and I fishtail all over the place. I've played with it (on empty streets of course) and on icy roads in 4wd with the LSD in the rear and open front, I can get the back end fishtailing all over, and still keep it pointed in the right direction with the front wheels. It's kinda fun actually. :twisted:
 

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Yes most sunvisors typically say not to run a 4x4 on dry pavement...or owners manuals.
 

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i broke a left cv shaft in a safeway parking lot cause my friends thought it was funny to lock in my hubs. tho it was a 86 with weak cv's, it still made me mad. dont do the 4x4 on dry, bad bad.
 

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the only cars/trucks you can do that on is ford with the 4 auto system its 2 wheel drive still traction is needed and the front engage then once traction is restored then disengage i know others have it and such but working with ford and was told they have it for that reason to use on rained or icy roads it can bec cuse and work fine up to 90 mph but dont have it on if you are making U-turns really hard on front axle when it engages my ex did it and it snaped a cv shaft
 

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Sags said:
Yea, you shouldn't do that again. It's bad for your truck, and dangerous too.

The binding your talking about comes from the fact that there is no central differential, like in all-wheel-drive vehicles.

When you're in 4wd (doesn't matter high or low, all that is is a gearing change) both the front and rear diff are driven at the same speed through the transmission/transfer case. But when you go around sharp corners your front wheels actually need to travel farther, but since in 4wd they are locked to the same RPM as the rear this caused the binding your talking about. This is why if you read the owners manual in any 4wd vehicle it will tell you not to run 4wd on dry asphalt or any other high traction surfaces, it can lead to dangerous understeer, and damage driveline components too.
I think you mean to say....The outside two wheels need to travel further, while the inside wheels need to travel a shorter distance....Meaning left or right side have to spin at different speeds. LSD was created for this reason, providing a better all around axle. One tire typically receives the power all time allowing the other to free spin according to the road. Until the "powered" wheel looses traction and clutches, springs, and etc...go into play spreading the power between the two wheels....Least this is how I under stand turning, and LSD's...I don't think turns typically affect wheel speed front to back, just side to side.
 

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Many newer vehicles and quite a few fullsize trucks from the '70's and '80's had full time 4WD. They were meant to be in 4wd all the time. All Isuzu's other than those with the TOD system are part time systems. Like Sags said there is no center diff to release the driveline bind and something will break. This system is meant for limited traction use. Some late Troopers and the VX's have TOD. This can be run on dry pavement I believe.
 

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I don't think turns typically affect wheel speed front to back, just side to side.
Sags is right. Think about what happens when you drive around a tight hairpin corner. You have to drive the front end wide to allow the inside rear tire to clear the corner. The front end has to go farther and faster then the rear around the corner. Its the same with any turn, just to a lesser degree. I run over curbs all the time with rear tires of my extended length work van LOL.

Some late Troopers and the VX's have TOD. This can be run on dry pavement I believe.
Yes. There actually isnt any choice since TOD does not have a 2wd option. Only choices are TOD or 4lo.
 

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-88- said:
I think you mean to say....
Nope, I meant exactly what I said. Read it again.

-88- said:
The outside two wheels need to travel further, while the inside wheels need to travel a shorter distance....Meaning left or right side have to spin at different speeds.
True, but that's only half the story.

-88- said:
I don't think turns typically affect wheel speed front to back, just side to side.
False, when in a turn the front must wheels go farther then the back wheels, this is because the front wheels steer and the back don't. So unless you have 4 wheel steering... ... Which is why driving on asphalt 4wd is a bad idea, not only will it bind up the transfer case -since the front wheels are trying to turn faster but can't- But it will also cause understeer -because the front wheels can't turn as fast as they need they will break traction.

Here I found a picture

Notice that the front wheels turn ad a greater radius then the back. So in a turn the combined RPM of A+B is greater then that of C+D. So when you're in 4wd and the T-case is powering both, at the same RPM something has to give.

A technical explanation: http://www.4x4abc.com/4WD101/def_turnpart.html

Like squatch and myself pointed out, this is why All-wheel-drive and full-time-4-wheel-drive vehicles have a center differential, in addition to the one in front and back.

Bottom line is RTFM if it says not to engage 4wd on high traction surfaces then don't do it.
 

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Enemigo said:
What the OP is actually asking is, "Are wet roads considered a "high traction" surface?"
I think so, if you're losing traction that bad on wet roads it means either, your going to fast and hydroplaning, or your tires have no tread left and you're hydroplaning. Either way 4wd does nothing to help, it only worsens the situation by adding understeer to the mix.

Also I think the biggest concern on wet roads is stopping, and 4wd doesn't help with that either. Plus even on very wet roads people will do up to 45mph, which is too fast for 4wd on any surface IMO, because although you will always get some understeer on low traction surfaces, 4wd makes it worse. Even on gravel and dirt at 45mph in 4wd you can definitely notice the understeer, and it's scary :shock: Ask me how I know, or better yet ask the tree that dented my FR fender. I learned the hard way that part-time 4wd does not work for rallying. Been there done that, will never run 4wd at 45mph even on dirt/gravel roads now, at least not any with corners.
 

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-88- said:
Sags said:
Yea, you shouldn't do that again. It's bad for your truck, and dangerous too.

The binding your talking about comes from the fact that there is no central differential, like in all-wheel-drive vehicles.

When you're in 4wd (doesn't matter high or low, all that is is a gearing change) both the front and rear diff are driven at the same speed through the transmission/transfer case. But when you go around sharp corners your front wheels actually need to travel farther, but since in 4wd they are locked to the same RPM as the rear this caused the binding your talking about. This is why if you read the owners manual in any 4wd vehicle it will tell you not to run 4wd on dry asphalt or any other high traction surfaces, it can lead to dangerous understeer, and damage driveline components too.
I think you mean to say....The outside two wheels need to travel further, while the inside wheels need to travel a shorter distance....Meaning left or right side have to spin at different speeds. LSD was created for this reason, providing a better all around axle. One tire typically receives the power all time allowing the other to free spin according to the road. Until the "powered" wheel looses traction and clutches, springs, and etc...go into play spreading the power between the two wheels....Least this is how I under stand turning, and LSD's...I don't think turns typically affect wheel speed front to back, just side to side.
Thats not quite right either. The part about the inside and outside having to spin at different rates is 100% spot on. The way the LIMITED slip differential works,at least the way OUR LSD works,becuase its a clutch type is that the clutches keep the axle locked normally. One wheel does not spin freely normally,the differential is locked by the clutches normally. When you go around a corner when the is enough torque on the clutch it slips allowing one side to turn at a different rate and it acts like a normal open differential. There are other kinds of limited slip differentials too. Some use fluids and some use gears.

The terms you will see describing the rear end are an "open differential" which is what most cars have,a LSD or Limited Slip Differential, and a "Spool" which means theres just a solid axle between the two wheels and they can never spin at different speeds. (very bad for turning,especially if your wheels cant slip). Here is how an open differential works. Its pretty much the best explanation ive ever seen of it.

 
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