I was driving through the snow at my buddy's property the other day, and needed to put in 4 lo to get back out to street in one spot.

He asked me if 4 lo locked anything up. I didn't think so, but thought I'd check.

Was he talking about Manuel hubs?

nope, just a lower gear ratio so you go slower at the same engine speed and gear compared to 4hi.

I know what 4 low vs 4 high does... I was asking about his buddies question.. if he was asking if he locked up the hubs

i was replying to the OP...

your front hubs "lock" in if they're automatic once you move forward a bit with 4wd engaged. the diffs will still be open unless you've put a locker in.

yea, the hubs lock in, but thats just until the LSD kicks in and one wheel will slip.
unless you have a locker in it, but if you had a locker in it you'd know the ansewr to the question....if that makes sense.

correct me if im wrong, but i think thats how it goes.

yea, the hubs lock in, but thats just until the LSD kicks in and one wheel will slip.

The hubs are on the front and connect the wheels to the front diff, which will still be an open diff unless a locker is installed.

The LSD, an option on 1st gen Xterras, is for the rear only, and will more or less allow the wheel with more traction to get some engine power (a good thing). A normal (non-LSD) diff will only give power to the wheel with LESS traction than the other side. Kinda bass-ackwards for offroading, but it's designed that way for the street. There's a point where limited slip still slips, though, and it depends on the LSD in question. In ours, I recall seeing it's something like 50 ft*lbs difference between wheels and it will slip.

I was driving through the snow at my buddy's property the other day, and needed to put in 4 lo to get back out to street in one spot.

He asked me if 4 lo locked anything up. I didn't think so, but thought I'd check.

I think that he was refering to locking the transfer case, if he is used to full time 4wd, some of them do have a locking central diff (transfer case). When a part time is pt in 4wd it locks in the transfer case at that time.

With AWD and full time 4wd there has to be a way for the drivetrain to slip so that it does not bind up and break when there is good traction.

cool - thx for the info. Just for clarity - the hubs and LSD, etc. - that is for 4wd vs 2wd, regardless of 4 hi and 4 lo, right?

He had a jeep w/ front and rear lockers, so I think he was wondering whether it had some kind of locker effect similar I think to what graniteX mentioned. Now his ques makes more sense what he may have been referring too.

So what is really going on in 4lo is that I get lower speed (with more torque)or rather more torque at same speed maybe better said so I can get over the hump without spinning tires as easily - if I understand it all correctly.? This was my answer to him anyways.

Thanks again!

Close.

Think of 4 lo as the bottom gears on your ten speed bike, and 4hi as the 6-10 speed range....with the t-case shifter making the chain go to the little pedal sprocket in Lo, and the larger sprocket in Hi.

In ADDITION to that, 4wd also locks the FRONT AND REAR diffs together.

Locked together is NOT the same as locked, it just means involves the front and rear output of the t-case.

LSD is only in the rear on X's....the front diff is open.

An open diff sends torque to the FASTER wheel...as, on the road, the outside tire has further to go than the inside tire for the same curve....

...and therefore has to go faster to arrive at the same time as the slower inside wheel.

If you had to push something around a curve, you'd push at the outside, its just easier, and you have better leverage, etc....


So that means the outside tire is the one tire that gets the ooomph....and the INSIDE TIRE COASTS.

Now, this works fine on the road...but, off road, where a tire might slip if it loses traction, or gets hung in the air, etc....

....That means that the slipping tire suddenly went FASTER, and, gets the ooomph...and, the OTHER TIRE JUST SITS THERE....NOT helping you move (It thinks its coasting around a turn...)

This can mean you have 1/2 your tires on solid ground, and be unable to move, as only the slipping tires are being driven.

An LSD works by locking the passenger and driver's sides together - with clutch packs in an Xterra.

The clutch packs are designed to keep the two sides locked together unless the DIFFERENCE between their speeds is so great, that the drive train would bind (As in two tires going the same speed, but one having to go further....and the drive train winding up until the tire chirps or skitters, etc...releasing the tension...when it snaps free of the bind)

The point the LSD lets go is called the break a way torque, or BAT.

The 00-01 X's had a higher BAT, ~ 80 ft/lb, the 02-04 X's had a very low BAT, like 34 ft/lb or so. The earlier pathfinders had a BAT of ~ 180 or so, and so forth.

So, off road, when one tire slips, the LSD holds on until the BAT is reached....so that the tire with traction can try to move you up to that point, and then the pack lets go.

When it lets go, its still not OPEN, its just LIMITED to that BAT...so it can still try to push you along, but only at the BAT's limit.

:wink-big:

Awesome!!! Thanks again.

This raises additonal questions for me if people want to keep playing. :)

Q1) so 4 Lo additionally locks the front and rear output together... How is this different than when in 4hi? Just curious as to what then this does at the wheels since its not 'locked' in the more traditional sense?

Q2) So front is open diff, which give torque to faster spinning tire for curves (faster turning outside wheel). So why then when I pull into a parking space in 4HI, while turning, I feel that 'skip' or 'jitter'? I realize answer should have been I didn't do it in the first place, but... just something I wondered as reading through the explanations. :) ???Maybe becuase the front and rear require different speeds because at different point in the turn - yet with same gearing would cause the front and rear to spin at same rate??

In ADDITION to that, Lo also locks the FRONT AND REAR diffs together...where as 4 hi doesn't.

Locked together is NOT the same as locked, it just means involves the front and rear output of the t-case.

I've been wondering about the locked front to rear part since I got mine. I've seen it often advised to not drive it on dry concrete while in 4 hi. If the 4wd system isn't locked front to rear there should be no issues with driving on the road while in 4wd. I've tried Googling for the info, but so far all I've found is what's been on here.

In 4 hi or low, there is one output speed from the Tcase. It goes to both the front and rear axles. That's why you get a jitter making a sharp turn in either 4wd - the front and rear axles are going in different sized circles, and therefore the wheels are skipping on the ground to relieve this stress in the drivetrain.

So for our Xs, 2wd means the wheel on the rear axle with the least grip gets power. 4wd means that the wheel on the rear w/ the least grip gets power, and up front the wheel with the least grip gets the same exact driveline speed from the Tcase.

Having a LSD or locking diff (not to be confused with autolocking or manual locking hubs) changes things for the better, but I'm done typing.

In 4 hi or low, there is one output speed from the Tcase. It goes to both the front and rear axles. That's why you get a jitter making a sharp turn in either 4wd - the front and rear axles are going in different sized circles, and therefore the wheels are skipping on the ground to relieve this stress in the drivetrain.

So for our Xs, 2wd means the wheel on the rear axle with the least grip gets power. 4wd means that the wheel on the rear w/ the least grip gets power, and up front the wheel with the least grip gets the same exact driveline speed from the Tcase.

Having a LSD or locking diff (not to be confused with autolocking or manual locking hubs) changes things for the better, but I'm done typing.

I understand how locking differentials work. My question was related to the function of the transfer case. In most 4x4 vehicles when the t-case is put into 4x4 hi or lo, the case becomes locked front to rear which makes the wheel with the least traction both front and rear turn at the same speed. This causes the binding problem on pavement when making turns because there is no slip front to rear to allow for the difference in wheel speed from front to rear. In All wheel drive, and some 4 wheel drive, vehicles there is a center differential, or a t-case that acts as one, which allows that front to rear slip to not cause issues in on road driving. The issue is that this reduces the off road ability, so most off road oriented vehicles have the locking transfer case.

My question is whether the Xterra, in 4 hi, has a locked transfer case, or an open transfer case (acting as a center diff).

Yes, in 4h or 4L the driveshaft, and the propeller shaft are tied together, as one spins so does the other. That is why it is recomended not to use 4wd either high or low on high traction surfaces ie pavement.

Yes, in 4h or 4L the driveshaft, and the propeller shaft are tied together, as one spins so does the other. That is why it is recomended not to use 4wd either high or low on high traction surfaces ie pavement.

This is why I'm asking, because what you are saying totally contradicts what TJTJ said...

In ADDITION to that, Lo also locks the FRONT AND REAR diffs together...where as 4 hi doesn't.

Locked together is NOT the same as locked, it just means involves the front and rear output of the t-case.

Hello, In most vehicles...one locker is better than two LSD units....
Too bad there is NO reasonable price electic lockers for the Xterras

We saw a possible front LSD for the front 02's Xterrra design for the Nissen P/U they said it should fit? ...anyone install one?

Aloha,

look at it this way, your x is a 2 wheel drive vehicle resulting in 100% of the engine power going to the rear axel, when you pull the lever to put it from 2wd to 4wd (hi or lo) you are guaranteeing the front axel get only 50% of the engine power and the rear gets 50% of the engine power, they are in affect tied together, not to be confused with AWD cars that have a center diff that decides where the power goes (on a side note, never tow an awd, or 4x4 in 4hi or 4lo with 2 wheels on the ground and 2 up) the difference between 4 hi and low is that (in a crude way) if the engine turns once in 4hi it turns the wheels 5 times, but in 4lo the same single rotation of the engine will only turn the wheels 1/2 of a rotation. I know that isn't correct to gearing, but I think it makes my point...I guess you could install switches in your 4X4 sifter and electric lockers to make the diffs lock in 4lo, but that seems like a lot of work...

This is why I'm asking, because what you are saying totally contradicts what TJTJ said...

There's no contradiction, they're just talking about slightly different things...

A differential has one input shaft and two output shafts. The Xterra has differentials on the front and rear axles. Each has an output to the driver-side and passenger-side wheels, and each has an input from the transfer case.

A transfer case with no differential also has one input shaft (from the transmission) and has two output shafts, but the output shafts will always rotate at the same speed when in 4-hi or 4-lo.

When you go around a tight corner the wheels on the inside and outside have to travel different distances. The differentials accommodate that difference.

However, when you're going around a tight corner, the front of the truck also travels a larger distance than the rear of the truck. In an Xterra with no center diff, that's a problem - the front differential's input shaft "wants to" rotate faster than the rear differential's input shaft. The only way to keep them both turngin at the same rate is for the tires to scrub against the pavement a bit.

In a car with a AWD and center differential, turning tight corners is no problem, because the center diff takes care of the difference between the front diff's input shaft and the rear diff's input shaft.

Make sense now?

Don't make sharp turns on any pavements while in 4WD!!
I don't know much about 4WD but I think I read in the owners manual that it is not good for it.

Someone correct me if im wrong please.

Don't drive on pavements while in 4WD!!
I don't know much about 4WD but I think I read in the owners manual that it is not good for it.

Someone correct me if im wrong please.

Fixed it for you

wellllllllllllllllllll....I just don't get it.

Just dont drive on pavement in 4wd, low range or high, it is just a bad idea. that all. not a big deal.