Question from a "non mechanic"

I thought I had figured out that the difference between the Taco selectable 4WD (and the reason we cannot drive on dry pavement with it engaged), is because there is no front differential. Something that only the AWD or full time 4WD vehicles had.

Then I see a thread or two on here about front diff issues like vibrations or bearings, etc., and I am confused again.

Do they have a front diff, and if so why cant we drive on dry pavement with 4WD engaged?

 

welcome to tacoma world.
I can't answer youre question, but i'm sure someone can.

 

4wd tacomas have front differental. It's not reccomended to drive on pavement because the tires have nothing to "slip" on when the 4wd is locked. Easy way to break front CV's,u joints, and anything in transfer case.

Basically, don't do it.

 

This, only operate 4x4 off road or on slick or snowy surfaces. There are warnings and what not on the visor I believe.

 

I know what Joe said is true, and I have felt the binding while turning with 4WD engaged. My question was, I thought it was because there was no front differential? If there is a front differential, why is it not like a AWD which also has a front differential?

 

AWD has a center transfer case, with shafts going to front and rear axles. Not so much a differential

 

The transfer case of an AWD acts as a differential, avoiding the binding which occurs in an old-fashioned 4WD when the front wheels are turned.

 

The front differential on trucks with 4wd are not designed for road use, they do have a differential. They are only there from factory so that if you do have to go through some sort of "offroad" that they are capable of it. They need to spin "differentialy", if you use lockers or locked diffs. it abuses them greatly.

I also wonder why they can't be used on the road though, and not even dealers or mechanics can answer it they just say that it isnt advised

 

This^^^ AWD has a center differential, so there are three. Our tacos just have differentials at the axles.

 

AWD has a center differential (usually in the transfer case) that allows the front drv shft & rear drv shft to turn at different speeds so there is no binding in the drivetrain, tacoma's transfer case locks both front and rear drv shfts together (both must turn at the same speed), which is why it's recomended not to operate on dry pavement

 

Winner!

 

The biggest difference between an AWD system and a 4WD system is a center differential.

This center differential allows the front and rear axle assemblies to spin at different speeds, much as your front and rear differentials allow differences in speed from side to side as you turn a corner.

I hope this answers your questions. If not feel free to ask for clarification.

 

Damn.. beat me by 2 minutes..LOL.. Nice explanation..

 

but isn't this only true if you had a locker in the front? tell me how one tire couldnt slip while the other has traction

 

the driveshafts are locked together not the cv's.

 

Once you lock into 4wd, you give power (unless you have front/rear lockers) to one front tire, one rear tire. Now, you have just locked the transfer case to spin both those tires. If you make a tight turn on pavement, one tire will try to spin faster, the other one slower on the same axle. Something has to give.

 

a locker goes inside the differential carrier, replacing the spider gears which spin freely,, a locker causes friction in the diff to apply torque to the wheel with traction while the other is in the air

 

yea i forgot that the transfer case on the taco locks the front and rear at same speed i was thinking of a awd case

 

So much mis-information in this thread, but these 2 post hit the nail on the head. OP I'd suggest you do some research on what differentials do and how they work

Edit: This vido should help you understand how a diff works

http://www.youtube.com/watch?v=K4JhruinbWc

 

not totally true, when you lock into 4wd, you are engaging the front and rear diff's; with equal traction at all 4 tires they will all pull the same.

Now if you have one tire in the mud or on ice an open diff will send torque to the tire with the least resistance wether front or rear