4x4 help

Hey guys,
In trying to understand the different 4x4 systems, I’ve learned about part time 4x4, full time and awd) I understand third gen tacos have part time, and it’s considered the best and “real” type of 4x4 out there.
My question is, I read that on a part time 4x4 system like us tacos have, that the front axle locks when you engage the 4x4. But then why do I hear about people getting front aftermarket lockers?

 

Google the following : how does 4x4 work

 

No Tacoma’s have factory front locking differentials. TRD offroad and Pro models have rear lockers. I hope someone can explain this better than I can.

 

I think you are referring to ADD. Auto Differential Dissconnect.

 

The front axle locks when you engage 4x4 in the sense that it locks it to the rear axle through the transfer case because we don’t have a center differential. It is not locking the axle like a locker which forces both wheels to spin at the same rate.

 

Unless you have a “locker” you have open diffs.
When you “lock into” 4wd all you are doing is making a connection between the two diffs.
So you get power to the front and rear.
HOWEVER,

Even though you are in 4wd you do not have 4 WD.
THATS WHERE THE LOCKERS COME IN.
you may have heard the phrase “one wheel peel”
One tire spins like in snow and the other one doesn’t do anything.
Well the same in the front. One wheel has the power available.
A locker connects both wheels on a given axle internally so when one wheel turns the other does also.
So you are able to apply power to both wheels.
So if you have “lockers front and rear” and you engage 4wd then you actually have the ability to apply power to the ground from every wheel.

 

Gotcha. That’s where I was getting confused from the article I read that said:

“
The Tacoma’s 4WD System (and Most Truck 4WD Systems, For That Matter)

The Tacoma – like a lot of pickup trucks – uses a part-time 4WD system. The front differential locks, which means that the Tacoma’s 4WD system should only be used on surfaces with limited traction. Using the Tacoma’s 4WD system on dry pavement should be avoided, especially if you plan on taking any turns.

In terms of engaging the front wheels, the Tacoma uses a center axle disconnect system. Basically, a 4WD Tacoma is just like a 2WD Tacoma until the 4WD system is engaged, as the front axle is disconnected by default.”

 

but with alsd/ trac right?

But what if both tires are getting good traction on each axle, is power then going to all 4 wheels?

 

Unless you have a diff lock you have open diffs.
Trac applies the brakes on the spinning wheel to transfer the power to the other side.

Good traction then yes equal power but we are talking low traction conditions.
So you lose traction with open diffs and everything goes to that wheel with low traction.
Locker keeps the torque equal to both wheels even though the wheel is off the ground it will
Send the torque to the other wheel.

 

Gotcha, thanks. So open diff and electronic brake assisted lsd correct? Instead of mechanical

 

That’s the ticket buddy...

 

Thanks. So then if someone asks if a third gen Tacoma has an lsd, they all do, just electronic ones and not mechanical?

 

Another thing to understand is why open differentials are necessary. They sound like a bad idea, but they're only bad when there's low traction. With normal use, like every day street driving, you don't need power to both wheels. The open differential allows each wheel to spin at different speeds. If you go around a curve, the wheel on the outside of the curve has to travel a little bit longer of a distance than the one on the inside of the curve, because the radius of the arc is greater on the outside. The difference is slight, but it matters. The open diff allows that outer wheel to turn a little bit faster. This allows better handling at higher speeds, longer tire life, and less wear and tear on the drive train.

You may have heard of people welding the differential. This permanently "locks" the axles on each side of the differential to each other so they have to spin together. A "spool" is a piece of metal that does the same thing, but is technically removable if you disassemble the whole differential to take it out. Welded and spooled diffs are usually only used on dedicated off road rigs or racecars. Locked differentials with good traction just tears the shit out of everything.

Hope that helps!

 

Your going to get lost in terms.
Your going backwards..

A locker is a locker. Ours are “electronically “ activated.

I’m going to get turned around trying to say it right.

LSD are mechanical.
Trac and open diff are brake controlled power transfer.

My head hurts now..

 

Very well said.

Done enough of welded diffs.
Glad he didn’t ask about that.

 

An lsd is a limited slip differential. It senses that one wheel has low or no traction and sends power to the other side. They are better than nothing, but aren't tough enough for serious use off road. Also, a locker makes them turn all the time, so you don't get any spinning unless both sides loses traction. An lsd lets the one wheel spin briefly before sending the power to the other wheel, so it could, in theory, slow or stop your progress. As mentioned above, they are mechanical and involve a set of clutches. Frequent engaging and disengaging as can occur with heavy off road use can burn them up or break them.

 

Another drawback of a lsd is that brief moment of spinning can cause your rig to start to slide on really slick stuff. Having both wheels start turning at the same time reduces that risk some.

 

Wait, I thought our trucks have a electronic lsd? Sorry if I’m misunderstanding. I know we don’t have mechanical ones that sometimes are options on other trucks, but don’t we have the electronic version?

Btw I have a sport so not the OR or Pro.

 

From what I can gather with some quick looking, older Tacomas (I think pre-2009) had a traditional mechanical LSD. It appears they replaced it with some kind of electrically operated LSD in 2009. I'm not familiar with exactly how it operates, but it does the same thing as a traditional mechanical LSD. An electronic LSD is not the electronic locker that is available in the off road and pro models, however. It is still an LSD.

 

Think about it this way as wheels that get drive power:
4x4 in 2WD = 1
4x4 in 4WD = 2
4x4 in 4WD with RR Difflock( OR and PRO) = 3

If you have equal traction on all 4 wheels, all wheels will drive it in 4WD, but if you are in slippery conditions refer to my above.