This has most likely been covered b4 but here goes.

Is it always necessary to reverse 8-10 feet when switching back to 2hi? (as per owners manual). the 4wd light goes out a few seconds after switching the shifter, does this mean the hubs are already disengaged?

When driving in patchy ice(100 yds heavy ice - 100 yds dry pavement) is it ok to leave it in 4 hi? or does this cause binding problems?
it seems a pain to switch every few minutes.

Yes, it's been covered before...
The hubs don't disengage unless you back up (technically, drive in the opposite direction from when you last had 4x4 selected).
Anyway, if you don't unlock you're only causing the axles and front driveshaft to turn. No big deal. It's a small hit on your gas mileage, and puts wear on the parts, but if you only do it now and then it's OK.

You'll be OK leaving it in 4Hi when driving on surfaces where it's slick then grippy, just be sure to throw it in 2Hi when taking anything tighter than a mild curve on a grippy surface, that's where you can run into binding quickly.

Brent

thanks for the quick response,

so does this mean the 4wd light is only an indicator of where your shifter is, and has nothing to do with the current gearing or hub condition?


[This message has been edited by bryanx (edited 02-16-2001).]

the 4 wheel indicator is where your transfer case is in. when you switch from 4 to 2wd it takes a few seconds depending on speed to actually get it back into 2 wheel drive. the light stays on as long as the transfer case is still in 4 wheel drive. if you want to know what true binding feels like leave your hubs locked and try to do a U turn. you feel what binding is.

if you leave your hubs locked you can switch in and out of 4wd and a higher speed than 25mph also. the 25mph applies to the hubs really.

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Silver Ice Xterra Xe
4x4 auto 3pk

[This message has been edited by Ag_xterra (edited 02-16-2001).]

question: when the hubs are locked in 2wd mode, are the 2 front wheels rotating at the same speed?

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That has nothing to do with the hubs, it's just physics.

When driving straight, all 4 wheels turn at the same rate.

When turning, all wheels turn at a different speed because they are all travelling through a different radius.

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Regards,
Ian

xoc, i understand the concept that all 4 wheels travel on different path when turning. but what i don't understand is about the hubs. what are their purposes? I'm no mechanic, but my guess is that the hubs lock the 2 front wheels when engaged in 4wd while the transfer case locks the front & rear axles (again, just my uneducated guess). and when shifting back to 2wd & leaving the hubs locked will hurt gas mileage & promote component wear. why is that? (pardon me for the rapid fire questions)

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Here's the deal. If you select 4WD, the transfer case starts sending power to the front driveshaft, which connects to the front diff, which connects to the front axles. With the hubs locked, those axles can turn the wheels. When they're unlocked, they can't. If you had manual hubs and they were turned "off" that would be exactly what happened. Everything but the wheels would be under power. With auto hubs, they axles turn a bit and cause the hub to engage them and therefore the wheels start being powered.
Once you deselect 4WD, the wheels will rotate due to the vehicle movement, which will spin the axles and driveshaft that are no longer connected to the power from the engine. Once they're unlocked, everything between the hub and transfer case is not moving, the front wheels spin just as if there were no axles up there at all.

Brent

Here's the deal. If you select 4WD, the transfer case starts sending power to the front driveshaft, which connects to the front diff, which connects to the front axles. With the hubs locked, those axles can turn the wheels. When they're unlocked, they can't. If you had manual hubs and they were turned "off" that would be exactly what happened. Everything but the wheels would be under power. With auto hubs, they axles turn a bit and cause the hub to engage them and therefore the wheels start being powered.
Once you deselect 4WD, the wheels will rotate due to the vehicle movement, which will spin the axles and driveshaft that are no longer connected to the power from the engine. Once they're unlocked, everything between the hub and transfer case is not moving, the front wheels spin just as if there were no axles up there at all.

Brent

Offroad x,

I think maybe i have it. Are you saying that when 2Hi has just been selected and the hubs are still locked, that the front axle is spinning but not being powerd by the engine(the transfer case is disengaged). Right?

If im wrong forget it, I give up.

Bryan.

[This message has been edited by bryanx (edited 02-20-2001).]

Don't give up. You've got it.

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bryanx,

Your front driveaxles have a set of splines that "float" with the hub unlocked. This means that they freewheel like the front hub of a 2WD vehicle. In autolocking hubs, when torque is applied to the front drive assembly, pressure is applied to a spring and a gear in the hub slides inward to engage the drive axle, locking the hub to the axle. Auto locking hubs can take a foot or so to engage due to the mechanics of it. Manual locking hubs do the same thing, minus the springs and extra distance needed to engage. When the manual hub lever is turned, it pushes the gear in mechanically and engages the front axle splines. The engagement is immediate. I think if you can picture this, you should have a solid grasp of how they work and what happens when they do.

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Gordon "The Warmonger" White

Interesting discussion, but I'm missing something: if the hubs are locked, but 4wd is disengaged, the front wheels are mechanically still locked to the front axle, although not powered by the front propeller shaft. So, does that mean that the front wheels, still locked to the front axle, must always rotate at the same speed? If true, that sounds like it would be bad for tire wear. I've driven a lot in 2WD with the front hubs locked and never noticed any problem, so I'm just curious.

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Isn't there a differential in the front? I presumed the missing differential, and the reason to avoid driving in 4WD modes on non-slippery surfaces, was between the front and rear axles.

AWD/fulltime 4WD vehicles offer that 3rd differential, and some even allow it to be locked out (at least I've ridden in Land Rover Discos with center locking diffs, but those may have been aftermarket).

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Yes, there is a diff up front. The wheels that steer need it far more than the fixed ones at the rear axle. It's the lack of a center diff that causes problems on grippy surfaces.

Brent

[This message has been edited by OffroadX (edited 02-21-2001).]

Tire wear would remain the same. But there is slightly more drivetrain wear since the driveshafts are moving while not needed. If the need for 4wd is anticipated, it is not neccessarily bad to have your hubs locked. Some people in snowy areas of the country leave their manual hubs locked all the time. The ability to shift into 4wd without getting out of their trucks is worth the added wear and tear on the front drivetrain.



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:wq!
wqbang@southeastxterraclub.org

There is a diff in the front, as said previously. The difference between AWD and 4WD is as was said, the center diff in the transfer case. AWD has a center diff with clutch plates similar to that found in an automatic transmission that splits the torque between the front and rear wheels. It eases the amount of power going to the front wheels by splitting torque (normally 60/40) among the axles. Usually the maximum torque delivered is 50/50. This makes the front wheels easy to turn even though the AWD is engaged all the time.

4WD on the other hand is a "lockout" situation. When you engage 4WD it engages a set of gears (some cases still use chains)in the transfer case that locks the front and rear drivetrain together. Because of this, full power is going to both the front and rear with no differential effect as in the AWD vehicles. This is what causes the hopping and pulling effect in the front end when turning tight radius corners in a 4WD vehicle. Another feature of 4WD is that they have a low speed on the transfer case. This is a gear that usually drops the engine to drivetrain ratio into the 2 to 1 range. It multiplies the torque by two or more, giving the vehicle more power to either pull itself or another load in low traction situations.

Hopefully I answered more peoples questions than people I have confused.





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Gordon "The Warmonger" White

so is it correct to say that in 4wd mode, both the front & the rear differentials are functional? and the only components that are locked via the transfer case are the front & rear drive shafts?

(again, pardon me for the questions on this topic, but it's hard to find folks like you with this kind of knowledge)

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In 4wd mode, the transfer case engages the driveshafts, which in turn engage the ring and pinions in both axles, which in turn engage the drive axles. If the hubs are locked, the axles will be engaged by the hub gears and the front wheels are under power. If you have manual hubs and they aren't locked, the drivetrain will turn, but the driveaxle will spin uselessly since the gear in the hub has not locked onto the splines on the drive axle. Auto locking hubs will engage whether you want them or not. BTW, it is not good for the drivetrain to drive with 4WD engaged and the hubs not locked. I don't want to give anyone the impression that they can do it without incuring the wrath of the 4WD gods.

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Gordon "The Warmonger" White

[This message has been edited by warmonger (edited 02-22-2001).]

Can you explain what is the problem in running with the transfer case in 4WD but with the hubs unlocked?

I ask because I have a Ford Ranger with manual hubs and pushbutton transfer case that uses a small motor to shift to 4WD. There is an electrical problem so I can't be sure it will shift when I need it so I've been tempted to just leave it in 4 and lock and unlock the hubs depending on road conditions.

Thanks for any explanation.

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Shouldn't hurt it really. Your gas mileage may be a tiny bit worse, but since the hubs aren't locked you shouldn't get any binding when turning.

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Eric Konarske
'01 Solar Yellow XE 3 Pk. 4x4