Do the rear wheels get powered in 4wd?

[SawyerRanger]

Ok, I know I'm risking a lot asking this (dumb) question, however I figured if I was gonna ask it, you guys would know best. Plus I can hide behind my computer screen if its really dumb.

Anyway, I was talking with my girlfriend's stepdad and we were talking about 4wd. He said most likely my left rear wheel doesn't get powered while in 4wd. I countered, saying that 4wd has to mean all four wheels get powered. He said that's not possible cause I don't have limited slip in my rear diff.

So my question, I have a 3.73 Open diff rear (8.8 28-spline if that matters in this situation). Does it get locked when I engage my automatic shift-on-the-fly 4wd? Or does only my front diff get locked? If it does get locked, how so?

The truck is a '99 with an auto tranny and auto 4wd.

Thanks guys, I was pretty sure of this before, but then he jumbled up how I thought about all this stuff, so I have to ask someone

 

[High Desert Ranger]

Ok, I know I'm risking a lot asking this (dumb) question, however I figured if I was gonna ask it, you guys would know best. Plus I can hide behind my computer screen if its really dumb.

Anyway, I was talking with my girlfriend's stepdad and we were talking about 4wd. He said most likely my left rear wheel doesn't get powered while in 4wd. I countered, saying that 4wd has to mean all four wheels get powered. He said that's not possible cause I don't have limited slip in my rear diff.

So my question, I have a 3.73 Open diff rear (8.8 28-spline if that matters in this situation). Does it get locked when I engage my automatic shift-on-the-fly 4wd? Or does only my front diff get locked? If it does get locked, how so?

The truck is a '99 with an auto tranny and auto 4wd.

Thanks guys, I was pretty sure of this before, but then he jumbled up how I thought about all this stuff, so I have to ask someone

If you have an open diff, nothing gets locked in the differentials. You are now applying power to the front and if that is also an open diff than I suppose that you could spin one front and one rear tire freely and still be stuck.

 

[SawyerRanger]

So my 4x4 is more like a 3x4?

 

[High Desert Ranger]

So my 4x4 is more like a 3x4?

Only if you get a wheel yo spin freely, but in most cases the front will pull you through your problem area on onto more trouble down the road.

 

[MikeWild]

That's why there's lockers, they ensure that both, (or if yer locked front & rear) all four wheels are getting power. Limited slip is similar in that once you get rear spin, it'll lock up the other tire.

 

[Captain Ledd]

hmm.. let's see if Ledd can explain this better...

4wd has a few parts to the system.

the rear axle get's power all the time, 2wd and 4wd. in that axle is a differential, it allows one wheel to spin faster than the other because the two rear wheels don't actually follow the same speed/distance around a turn. it's only a minor difference, but if it didn't allow this action, you'd definably notice it. Unless you have a limited slip, the power goes to the wheel with the least resistance, like electricity. So if you had a wheel up in the air, you wouldn't go anywhere because all the power is sent to that wheel. Limited slips send SOME of that power to the wheel with less traction (though generally if it's up in the air there is still not enough resistance to make it work).

The front wheels act the same way.

The transfer case is slightly different. since these are what's called "part time cases" meaning they're not meant to be run in 4x4 all the time, don't have this differential, because overall (average) the rear wheels don't travel the same speed as the front in a turn (though even things like tire pressure can play a factor). So it sends power to both front and rear axles evenly regardless of whats going on.

chances are neither of your differentials get locked. Lockers are pretty much aftermarket only and you'd probably remember installing or knowing about one, they can be $$$.

All 4 of your wheels get powered in 4wd, weather it can adequately make it to the ground is another issue.

 

[midget]

Technically with open diffs on slick terrain 2wd is really 1 wheel drive and 4wd is more like 2wheel drive.... however with no wheelspin its a true 4x4 once a wheel slips it takes all the power away from teh opposite side without a locker or lsd.

 

[Will]

With an open differential each tire delivers exactly the same torque to the ground as the tire on the other end of the axle. So if one tire slips and is delivering zero torque--the one that didn't slip just sits there and also delivers zero torque. When one slips you have no wheel drive. When neither slips you have two wheel drive.

On a 4x4 with two open axles you can certainly have no wheel drive. You go into a snowy ditch where both high-side tires can't grip, they spin and deliver zero torque and the well-planted lower tires also apply zero torque.


The axles are locked together through the transfer case. When in 4wd you can't spin just one tire. If the front is planted and you pick up a rear tire, it's not going to spin unless you also lose traction on a front. But the remaining tire still isn't delivering any traction to the ground--the one in the air just isn't allowed to spin very fast.

 

[dennis461]

..Anyway, I was talking with my girlfriend's stepdad..

I'd say, if your girlfriend is HOT, then stepdad is right.
If you're ready to break up, then he's wrong.

 

[SawyerRanger]

I'd say, if your girlfriend is HOT, then stepdad is right.
If you're ready to break up, then he's wrong.

Stepdad is right

And thanks everyone for your posts, this makes much more sense now, I really appreciate all of the info and fast response!

 

[5speedin2.3]

So my 4x4 is more like a 3x4?

If both differentials are open then your 4x4 would only be 4x2, but with one front wheel pulling.

Invest in two lockers if you want TRUE 4wd.

http://auto.howstuffworks.com/differential.htm

 

[OBX2003]

I get kind of tired of hearing MECHANICS saying that only the right tire is powered in an open rear. I think people say that because when you peel out on level pavement, the right tire is the one that spins. This is due to torque reaction lifting the right side of the axle slightly so it spins. Take your girlfriend's father out and put each wheel into a puddle seperately and see if the one in the puddle doesn't spin. But only when you are ready to break up. LOL

I agree with everyone who above said the differential lets the wheels turn at different speeds, so you can go around a corner. Wikipedia has a pretty good desription:

http://en.wikipedia.org/wiki/Differential_(mechanical_device)

Those of you (us, actually) with open rears can try this old trick: When one rear tire is slipping on bad terrain, put on the emergency brake enough to slow or stop the freewheeling side, but not enough to stop the vehicle completely. This will cause torque to transfer to the non-spinning side. We've done this forever with 2 wheel drive vehicles. I was even thinking of rigging up seperate brakes for the rear. That's if I am too lazy to bolt in a traction lok or whatever.

Have fun!

Bob

 

[85_Ranger4x4]

I get kind of tired of hearing MECHANICS saying that only the right tire is powered in an open rear. I think people say that because when you peel out on level pavement, the right tire is the one that spins. This is due to torque reaction lifting the right side of the axle slightly so it spins. Take your girlfriend's father out and put each wheel into a puddle seperately and see if the one in the puddle doesn't spin. But only when you are ready to break up. LOL

I agree with everyone who above said the differential lets the wheels turn at different speeds, so you can go around a corner. Wikipedia has a pretty good desription:

http://en.wikipedia.org/wiki/Differential_(mechanical_device)

Those of you (us, actually) with open rears can try this old trick: When one rear tire is slipping on bad terrain, put on the emergency brake enough to slow or stop the freewheeling side, but not enough to stop the vehicle completely. This will cause torque to transfer to the non-spinning side. We've done this forever with 2 wheel drive vehicles. I was even thinking of rigging up seperate brakes for the rear. That's if I am too lazy to bolt in a traction lok or whatever.

Have fun!

Bob

Another reason that the right usually the first to spin is the same reason old rangers lean, both the driver and the fuel tank are on the left side giving that side more traction than the right.

 

[Frank The Tank]

I love getting hung up in a stocker.
It's a 2wd locked in 4x4 rear right, and front left spin, beutifull!!!

Frank