AWD and 4WD


#1

Hello, I am new to these forums and had a hard time finding an answer to this question I had. Are transfer cases used in AWD and 4WD vehicles? or just in 4WD vehicles? I know AWD uses a center differential but also read they can have a transfer case. I’m an auto student and it’s just really confusing me haha. If someone could shed some light on this for me it would be much appreciated!


#2

It is vehicle and model even option specific. No general answer. For example a Honda Pilot has something call real time 4wd however it is really AWD.

Samples of vehicles with a transfer case AND center differential are Jeep products with certain options like the Compass, Cherokee, Grand Cherokee etc.


#3

AWD spins the spare tire as well as the four drive wheels.


#4

There’s no clear difference between AWD and 4WD. When I think of ‘transfer case’, I think of an ‘old style’ 4WD vehicle which normally is in RWD. It’ll have a lever or switch that can engage 4WD/AWD, and often has a ‘neutral’ setting where the engine is disengaged from both axles. Old style 4WD would have no center differential, and was engaged only in slick conditions. But “4WD” is a label now used for lots of vehicles that I would call AWD.


#5

Unless you live in “Snow Country” and feel you MUST drive during winter storms, AWD has more negative aspects than positive…Most drivers can live without it…


#6

Thanks for the replies. So to reply to andrewRA, something like the 2014 Nissan Juke would have a transfer case and center dif because you are able to select 2WD or AWD with a switch?


#7

No, it’s FWD-based, I think of ‘transfer case’ with RWD based pickup trucks and SUVs. In my opinion.

A transfer case is typically a large gear box hooked to the rear of the transmission:


#8

Don’t get hung up on the nomenclatures. A transfer case is any assembly that distributes the torque from the transmission output shaft to both the front and rear wheels. It can be a system engaged by the driver or be full-time.

The only thing that really matters is whether the system you have will meet your needs. Mercedes drivers have very different needs than building contractors, and the system designs are thus very different. The contractor might need to pull stumps, tow flatbed trailers with front end loaders on them, haul loads of concrete blocks, and carry a large fuel tank full of diesel fuel to his off-road equipment… driving on freshly turned earth, which can have horrible traction if it’s sandy. A Mercedes would not do that or survive that. A Mercedes driver wants smooth, quiet, highway rides with the ability to get home in the occasional snow storm. Construction-worthy trucks can’t offer the level of luxury that the Mercedes driver seeks.

I’m curious; was there a specific reason for the question?


#9

Back in the spring we were learning about transfer cases in my drivelines class. I was trying to refresh my mind with what we learned and these were one of the things I was confused with.


#10

Not every AWD has a center diff. GM and Chrysler use a transfer case that has a electronic lockup feature that engages the front axle only when the system sense rear slip. The AWD button on the dash connects the front drive axle to the transfer case and then waits for slip. AWD really should be called “part-time 4WD” but that printing wouldn’t fit on the button. The 4WD button on the same truck locks the front and rear axles together. In 2WD, the hubs on the front axle unlock so there is less drag and better MPG. AWD can be used all the time, 4WD should only be used in slippery conditions.

The itty-bitty SUV’s like the Rav 4 and CRV are normally FWD with a jack-shaft off the transmission to drive a teeny rear differential. No transfer case, all built in. Audi Quattro AWD cars are similar. No T case either, built-in.


#11

Mustangman, I would argue that they have transfer cases, they’re just not a separate assembly. I consider it analogous to a differential; people think that FWD cars don’t have a differential, but IMHO they do. It’s just incorporated into the transmission case.

Truth is, it’s all a matter of how one defines the terms. I tend to consider the term based upon the function they perform, others tend to attach the nomenclature to a specific assembly. Neither is wrong, neither is right. They’re just different perspectives.


#12

So it depends on the vehicle? and also someones perspective. Not every AWD has a transfer case, not every AWD has a center dif, some have a center dif incorporated into the transfer case? (I read some AWD cars have a center dif in the transfer case in my textbook)


#13

It’s a common question/confusion, the industry uses all kinds of lingo on this. Here are some helpful articles:
http://gearpatrol.com/2013/03/29/four-wheel-drive-vs-all-wheel-drive-everything-you-need-to-know/




#14

If somebody believes FWD cars don’t have a differential, they lack a fundamental understanding of automobiles

Is their logic, if the vehicle doesn’t have a pumpkin, it doesn’t have a differential?

That’s flawed logic, based on a lack of understanding

While we’re on it, I should point out that most people . . . myself included, quite often, actually . . . use the word transmission when we’re talking about FWD cars. That’s incorrect. Technically, they are transaxles. Many people use the word transmission, because they assume the person they’re talking to won’t understand the term transaxle.


#15

Great explanation of Trans axle vs transmission @db4690‌

We must also remember some front engined cars such as the C5 Corvette use a trans axle, The engine is up front and the trans axle is in the rear. Air cooled Vw Beetles also used a trans axle.


#16

When I think of 4WD, I think of vehicle that has a transfer case that doesn’t allow the front and rear differentials to rotate at different rates. And it may also have front locking hubs.

When I think of AWD, I think of a vehicle that has a center differential which does allow the front and rear differentials to rotate at different rates.

Tester


#17

@WheresRick‌

Excellent point about the Corvette and the old Beetle


#18

so is a Cherokee with the part time 4wd an all wheel drive? it still says don t drive on dry surfaces


#19

Thanks Tester, that’s what I’m starting to get at now. My remaining concern is can AWD vehicles have transfer cases?


#20

If it says not to drive on dry surfaces it’s 4WD. That’s because the transfer case won’t allow the front and rear differentials to rotate at different rates while cornering. And that can damage the transfer case.

Tester