# Does a four wheel drive car have a differential gear?



## Tedgey (Jan 29, 2016)

How about it motorheads?


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## Tatertots (May 14, 2016)

I assume a 4x4 would have 2 differentials


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## Tatertots (May 14, 2016)

3 if you count the transfer case, I suppose


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## Taxi Driver in Arizona (Mar 18, 2015)

Tatertots said:


> I assume a 4x4 would have 2 differentials


And a transfer case, typically. Lots of stuff to break on a 4x4.


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## Tatertots (May 14, 2016)

Teeeechnically the transmission could be considered a differential if we wanna split hairs since a "differential gear" is a fairly broad term.


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## rtaatl (Jul 3, 2014)

Yes it does with an open center differential so the front and rear axle turn independently at different speeds


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## Tedgey (Jan 29, 2016)

So then a four wheel drive would more accurately called a 2 axle drive?


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## Taxi Driver in Arizona (Mar 18, 2015)

Tedgey said:


> So then a four wheel drive would more accurately called a 2 axle drive?


Only if you want to sound like a noob.


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## Tedgey (Jan 29, 2016)

Taxi Driver in Arizona said:


> Only if you want to sound like a noob.


Well my understanding of 4 wheel drive is noobish to say the least so you know, represent.


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## Taxi Driver in Arizona (Mar 18, 2015)




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## Tedgey (Jan 29, 2016)

And then one last noobiathin clarification. The idea is to deliver power to all 4 wheels but not independently of one another? The two axles are independent but not the four individual wheels? That sounds like an engineering marvel.


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## Taxi Driver in Arizona (Mar 18, 2015)

Tedgey said:


> And then one last noobiathin clarification. The idea is to deliver power to all 4 wheels but not independently of one another? The two axles are independent but not the four individual wheels? That sounds like an engineering marvel.


Yes it is, and 4wd vehicles can have problems on dry pavement when turning because all four wheels are going at the same RPM. There are technical solutions to this problem but it starts to get very complex.


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## Tedgey (Jan 29, 2016)

Taxi Driver in Arizona said:


>


Nice. That's a good video. Thank you


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## Fauxknight (Aug 12, 2014)

The different types of differentials can be a big deal on 4x4 trucks depending on what you want to use it for, so yes, 4WD drive vehicles use differentials.

More importantly what is the basis of the question, or why do yo uh want to know?


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## Tedgey (Jan 29, 2016)

Taxi Driver in Arizona said:


> Yes it is, and 4wd vehicles can have problems on dry pavement when turning because all four wheels are going at the same RPM. There are technical solutions to this problem but it starts to get very complex.


Scientists do a lot of interesting things and have great and important ideas but they don't mean anything until the engineers put those ideas to use.


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## Tedgey (Jan 29, 2016)

Fauxknight said:


> The different types of differentials can be a big deal on 4x4 trucks depending on what you want to use it for, so yes, 4WD drive vehicles use differentials.
> 
> More importantly what is the basis of the question, or why do yo uh want to know?


I was more curious about the mercedes 4matic and what it is but I just got to thinking about what a 4 wheel drive actually meant. I thought it meant power is delivered individually to all four wheels but I didn't have any idea how that would work


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## Taxi Driver in Arizona (Mar 18, 2015)




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## Tatertots (May 14, 2016)

Things can get muddy when sorting out the differences between 4wd, 4x4, and awd.

All wheel drive is precisely what it implies. All wheels at every axle end are powered.

If 4x4, 6x4, 4x2, etc. is used then the first number states how many axle ends there are total and the second number states how many are powered.

4wd, 2wd, 6wd, etc. only states the total number of powered axle ends. 

Differentials are used in most all internal combustion engine powered vehicles. A differential may not necessarily be used in a 4wd or awd vehicle such as with a 4wd electric car that has motors in the wheels.


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## Fauxknight (Aug 12, 2014)

That's where a transfer case comes in, most 4WD or AWD vehicles use one to distribute power.

The transfer case is why you don't leave a 4WD drive vehicle in 4WD or even in on demand 4WD mode. Both modes keep the transfer case engaged which means a lot of uneccesary wear on the transfer case. Keep it in basic 2WD for day to day driving.

The exceptions to the transfer case rule are generally fully or partially electric vehicles. A Tesla uses independent electric motors on each wheel and some hybrids have a normal drive train for one set of wheels and independent electric motors on the other set (Rav4 hybrid, NX200H)


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## Taxi Driver in Arizona (Mar 18, 2015)

I think the important thing here is that if you're thinking of using a Mercedes for Uber, you're out of your everlovin' mind.


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## Tedgey (Jan 29, 2016)

Tatertots said:


> Things can get muddy when sorting out the differences between 4wd, 4x4, and awd.
> 
> All wheel drive is precisely what it implies. All wheels at every axle end are powered.
> 
> ...


The electric car was the other thing I was wondering about and also if they convert kinetic energy into stored electricity like the hybrids and whether or not that increases the life of the brake pads.

Of course I also wonder why so many corvette drivers crash when accelerating. There's a million videos on you tube and they all look like this






I guess it's a back end issue but I'd also guess that Jeff Gordon probably wouldn't have crashed there had he been driving that car. There are some questions that can't be answered on uberpeople


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## Tedgey (Jan 29, 2016)

Taxi Driver in Arizona said:


> I think the important thing here is that if you're thinking of using a Mercedes for Uber, you're out of your everlovin' mind.


I'm not. Just curiosity


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## Tedgey (Jan 29, 2016)

Taxi Driver in Arizona said:


>


Yeah. The first video I got. This one... I get that Mercedes has a nice budget for graphics but. ...


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## Fauxknight (Aug 12, 2014)

Tedgey said:


> The electric car was the other thing I was wondering about and also if they convert kinetic energy into stored electricity like the hybrids and whether or not that increases the life of the brake pads.


Regenerative braking.
Yes, most electric vehicles use it.
Yes, it dramatically increases the life of the brake pads.



> Of course I also wonder why so many corvette drivers crash when accelerating. There's a million videos on you tube and they all look like this
> 
> 
> 
> ...


Without even watching the video I can say it is indeed a backend issue, it's called rear wheel drive. Rear wheel drive is pretty much only used on high powered vehicles (sports cars, trucks) nowadays because its a much simpler/cheaper way to handle that much power. Front wheel drive is the standard for everything else, it simply provides much better/safer handling for any basic people mover.


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## Taxi Driver in Arizona (Mar 18, 2015)

Tedgey said:


> Yeah. The first video I got. This one... I get that Mercedes has a nice budget for graphics but. ...


Like I said, the solution to the problems of a standard 4x4 can get very complex.

Thank jeebus for German engineers.


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## Tedgey (Jan 29, 2016)

Fauxknight said:


> Regenerative braking.
> Yes, most electric vehicles use it.
> Yes, it dramatically increases the life of the brake pads.
> 
> Without even watching the video I can say it is indeed a backend issue, it's called rear wheel drive. Rear wheel drive is pretty much only used on high powered vehicles (sports cars, trucks) nowadays because its a much simpler/cheaper way to handle that much power. Front wheel drive is the standard for everything else, it simply provides much better/safer handling for any basic people mover.


Damn. You guys really did answer all my questions. It looks like a rear end problem because in every video, and there are lots, the back end just looks like it goes first. I think the drivers maybe lack the skills to live up to their imaginations as well.

Thank you very much for answering my questions. You and everyone else too. I appreciate you all taking the time to explain these things to me.


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## LAuberX (Jun 3, 2014)

A differential allows all cars to go around corners without squealing the inside tire.

It allows the tires on the same axle to turn at different rpms while cornering.

Simple.


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## Tedgey (Jan 29, 2016)

LAuberX said:


> A differential allows all cars to go around corners without squealing the inside tire.
> 
> It allows the tires in the same axle to turn at different rpms while cornering.
> 
> Simple.


Hey moderator, we're way past that. Show up on time next week!


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## Taxi Driver in Arizona (Mar 18, 2015)

The corvette crash was caused by the differential putting more power to one rear wheel than the other.

That problem is solved with limited-slip or locking differentials. Sometimes referred to as posi-traction.

Of course, the driver of the corvette was most likely an idiot.


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## njn (Jan 23, 2016)

Fauxknight said:


> The exceptions to the transfer case rule are generally fully or partially electric vehicles. A Tesla uses independent electric motors on each wheel and some hybrids have a normal drive train for one set of wheels and independent electric motors on the other set (Rav4 hybrid, NX200H)


The Acura RLX and MDX also use a twin motor unit for rear and the NSX for the front.

http://www.acura.com/videogallery.aspx?model=rlx#2016-rlx-video-acura-rlx-sport-hybrid-sh-awd


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## gearhead (Nov 30, 2015)

The more differentials you have the more weight you have.....and the less mileage you get. If you think you need a 4 wheel drive get one that has an AWD function, that way when can switch over to 4 wheel with a push of a button.


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## itsablackmarket (May 12, 2015)

all I know is Subaru and Audi have the best AWD systems.


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## Fauxknight (Aug 12, 2014)

itsablackmarket said:


> all I know is Subaru and Audi have the best AWD systems.


Subaru makes very inexpensive vehicles when you count in the fact that you get AWD with anything they sell, apart from the BRZ. My mother is on her 3rd Subaru I think, this one is an Impreza Wagon and gets 40ish on the freeway, pretty good a station wagon.


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## Fireguy50 (Nov 23, 2015)

Taxi Driver in Arizona said:


> The corvette crash was caused by the differential putting more power to one rear wheel than the other.
> 
> That problem is solved with limited-slip or locking differentials. Sometimes referred to as posi-traction.
> 
> Of course, the driver of the corvette was most likely an idiot.


That was just oversteer and an idiot driver trying to impress. Most computer controls are over exaggerated by the manufacturer. They can't fix stupid drivers, just compensate for a little weather.

Even the Mercedes Benz traction controls are exaggerated, no better than the Corvette


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