Want to make sure I understand the 4WD drivetrain

Spriter

Spriter

New member
Hello!

I just recently bought a 05 v6 t4r and have been loving it so far! Been doing some research into the internal components on this vehicle, and when looking at the drive train, I didn't realize it had a 3rd differential.

So, as far as I understand,
In 2HI, it is 2WD.
In 4HI it is AWD. <--is this true and is it comparable to say a subaru's?
In 4HI+center Diff locked, it is 4WD.

I tried to make some diagrams of it to make sure I'm getting it right and would love if you all could help me confirm my understanding of it.

The first three being diagrams to understand where it can send power. And the fourth being one showing it make an at-speed turn and the power delivery at that moment.
 

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I think you get the principals, or are pretty close to.

But technically, in diagram 1, shouldn't it be 100% for the rear driveshaft not 0-100%. The front would see the 0%.

Diagram 3, with the center diff locked, you will always have at least 1 tire on the front axle and one tire on the back axle receiving power so I dont think the 0-50% at each end of the t-case is accurate.
 
Yes, from what I understand that is how it functions. Make sure you exercise all modes of your 4x4 system (engage 4hi, 4lo, and center diff lock) at least once a month to ensure it doesn't get jammed up and stop working, leading to a very expensive repair!
 
Absolutely not. I have been in the 4wd truck world my whole life. AWD systems have a type of clutch in the transfer case which allows for slippage when turning sharp. Out cases in 4hi do not have that clutch and will bind up on dry pavement. Test it for yourself, it's simple. Pull into a parking lot, put it in 4hi, turn the wheels hard left or right, and GENTLY try and drive away. You will feel the whole truck sorta skip or slip and your tires will chirp due to the system binding. Not going to argue, this has been brought up many times. Your truck do what you want but you've been warned.
 
To add to this, some vehicles like the Jeeps with the 242 transfer case for example, have a 2wd, 4wd full time, 4wd part time, 4lo transfer case. In this case, the 4wd full time is designed to act like an AWD system and is safe to run on any terrain. For our runners, 2wd is your daily go to, 4hi is your normal use snow driving or light 4 wheeling go to, 4lo is your hill or rock climbing go to.
 
I need to make a sticky thread for this topic, nobody can agree and it even makes me confused.

V8's drive around in 4hi all the time, V6's apparently have the center diff lock as well so I am assuming they can too as long as the center diff is unlocked.
 
2016 4Runner SR5 said:
Absolutely not. I have been in the 4wd truck world my whole life. AWD systems have a type of clutch in the transfer case which allows for slippage when turning sharp. Out cases in 4hi do not have that clutch and will bind up on dry pavement. Test it for yourself, it's simple. Pull into a parking lot, put it in 4hi, turn the wheels hard left or right, and GENTLY try and drive away. You will feel the whole truck sorta skip or slip and your tires will chirp due to the system binding. Not going to argue, this has been brought up many times. Your truck do what you want but you've been warned.
Click to expand...

Im trying to gain an understanding, not argue.

The reason I was led to believe it has AWD characteristics is due to the fact that my truck has a lock/unlock function for the center differential.

And at least to my rudimentary understanding of them, if a differential is in an open position like that, and if you have 3 of them set up, as the t4r does, then it cant really bind and performs like an AWD system.
 
Last edited:
Inv4drZm said:
I need to make a sticky thread for this topic, nobody can agree and it even makes me confused.

V8's drive around in 4hi all the time, V6's apparently have the center diff lock as well so I am assuming they can too as long as the center diff is unlocked.
Click to expand...

Yes that is what my understanding is. I think people do not realize the center diff can be unlocked on them.

But maybe im misunderstanding something, looking at it from a purely mechanical point of view it SEEMS to be an AWD mode, maybe not electronically actuated, but a simpler, mechanical AWD system.
 
2016 4Runner SR5 said:
Absolutely not. I have been in the 4wd truck world my whole life. AWD systems have a type of clutch in the transfer case which allows for slippage when turning sharp. Out cases in 4hi do not have that clutch and will bind up on dry pavement. Test it for yourself, it's simple. Pull into a parking lot, put it in 4hi, turn the wheels hard left or right, and GENTLY try and drive away. You will feel the whole truck sorta skip or slip and your tires will chirp due to the system binding. Not going to argue, this has been brought up many times. Your truck do what you want but you've been warned.
Click to expand...

That is how the t-case in the 5th gens (non limiteds) and FJ's behave. However on the 4th gens, there is an actuator that locks and unlocks the t-case so you can de-couple the front and rear driveshafts and turn on concrete.

Case in point, the 4x4 V8 4Runners only have 4hi and 4lo drive modes, with the center diff locked or unlocked.

Since my truck is a 4x4 V8 I just switched it from 4hi to 4lo on concrete and turned sharp, no binding. Like I expected. This is great for trails where you need to turn sharp, just punch the center diff unlock button, make the turn, and re-engage it.
 
Spriter said:
Im trying to gain an understanding, not argue.

The reason I was led to believe it has AWD characteristics is due to the fact that my truck has a lock/unlock function for the center differential.

And at least to my rudimentary understanding of them, if a differential is in an open position like that, and if you have 3 of them set up, as the t4r does, then it cant really bind and performs like an AWD system.
Click to expand...

Yes, you’re tracking of the 4WD system in the 4th gen is exactly what I believe as well. 4Hi in the 4th gen is AWD. In the 5th Gen, the SR5 and trail it’s 4WD only. Hence what 2016 is saying... but the 5th gen is not the 4th. The 4th gen is a way better system IMO for your average person.
 
Last edited:
Spriter said:
Hello!

I just recently bought a 05 v6 t4r and have been loving it so far! Been doing some research into the internal components on this vehicle, and when looking at the drive train, I didn't realize it had a 3rd differential.

So, as far as I understand,
In 2HI, it is 2WD.
In 4HI it is AWD. <--is this true and is it comparable to say a subaru's?
In 4HI+center Diff locked, it is 4WD.

I tried to make some diagrams of it to make sure I'm getting it right and would love if you all could help me confirm my understanding of it.

The first three being diagrams to understand where it can send power. And the fourth being one showing it make an at-speed turn and the power delivery at that moment.
Click to expand...

You're correct, for your specific 4th gen model. I drive in 4HI (center diff unlocked) monthly without issue/binding with the same system.
 
Ok so I recently purchased a used (only 138k miles) v8 4.L 2004 sr5 T4R. And I have been reading about turning off and on the center diff with a button... mine doesnt have the button! Whats the deal? Was there a model that didnt have it? Did I somehow get jipped? Help!
 
category_theory said:
Ok so I recently purchased a used (only 138k miles) v8 4.L 2004 sr5 T4R. And I have been reading about turning off and on the center diff with a button... mine doesnt have the button! Whats the deal? Was there a model that didnt have it? Did I somehow get jipped? Help!
Click to expand...

Are you sure your truck is 4x4? Some models are rear wheel drive only, which would explain the absence of that button.
 
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