Center Diff Question

[Jerrydog]

I have a question about the Center Diff in the 4R. I am familiar with how an axle diff works how a LS diff works and how a locking diff works. I also understand how a transfer case works.... that said here are my questions.

What is a center locking diff? A traditional TF case which is located in the ceter of the drivetrain is locked, when engaged it transmits the same power to the front and rear axles. In some 4WD race vehicles they have an actual center mounted diff as part of the transfercase that will send a portion of the power to front or rear and its adjustable like an actual diff.

When Toyota refers to the center diff, what is it? Traditional TF case or a LS diff?

When you "lock it" what happens? does it lock the diffs in both the front and rear axles so you get actual 4wd (all 4 wheels ACTUALLY turn together)?

Anyone have a diagram form the factory manual on the drivetrain?

thanks

 

[scottm]

The center diff is a Torsen differential, not an open or LS diff, fairly sophisticated. Locking it means locking the guts so it is like a traditional 4X4.

 

[DocMT]

I have a question about the Center Diff in the 4R. I am familiar with how an axle diff works how a LS diff works and how a locking diff works. I also understand how a transfer case works.... that said here are my questions.

What is a center locking diff? A traditional TF case which is located in the ceter of the drivetrain is locked, when engaged it transmits the same power to the front and rear axles. In some 4WD race vehicles they have an actual center mounted diff as part of the transfercase that will send a portion of the power to front or rear and its adjustable like an actual diff.

When Toyota refers to the center diff, what is it? Traditional TF case or a LS diff?

When you "lock it" what happens? does it lock the diffs in both the front and rear axles so you get actual 4wd (all 4 wheels ACTUALLY turn together)?

Anyone have a diagram form the factory manual on the drivetrain?

thanks

We have a transfer case with an integrated center differential. When you lock the center diff, 50% of the engine's torque goes to the front axle and 50% goes to the rear axle. All four wheels won't necessarily turn together though because you'd need not only a locked center differential, but also locking front and rear differentials as well. In our 4Runners the center diff locks the front and rear driveshafts together, but the side-to-side traction is handled by the ATRAC system.

 

[M1911]

I have a question about the Center Diff in the 4R. I am familiar with how an axle diff works how a LS diff works and how a locking diff works. I also understand how a transfer case works.... that said here are my questions.

What is a center locking diff? A traditional TF case which is located in the ceter of the drivetrain is locked, when engaged it transmits the same power to the front and rear axles.

I would put it differently. When a traditional TF case is engaged, the front and rear driveshafts turn at the same speed.

When Toyota refers to the center diff, what is it? Traditional TF case or a LS diff?

It is a lockable, limited slip Torsen differential. When unlocked, it acts like a limited slip differential. It sends torque to both driveshafts, but they can turn at different speeds.

When you "lock it" what happens? does it lock the diffs in both the front and rear axles so you get actual 4wd (all 4 wheels ACTUALLY turn together)?

When you lock it, it acts like a part-time 4WD system. The front and rear driveshafts turn at the same speed.

Note, all 4 wheels DO NOT turn at the same speed. Not with the Torsen or with a part-time 4WD system. The only way all four wheels would turn at the same speed is if you had three locking differentials (front, center, and rear), and only a couple vehicles have that (Mercedes G500 and Wrangler Rubicon, IIRC).

See: Torsen General Frequently Asked Questions page
Torsen - Wikipedia, the free encyclopedia

 

[Jerrydog]

I would put it differently. When a traditional TF case is engaged, the front and rear driveshafts turn at the same speed.


It is a lockable, limited slip Torsen differential. When unlocked, it acts like a limited slip differential. It sends torque to both driveshafts, but they can turn at different speeds.


When you lock it, it acts like a part-time 4WD system. The front and rear driveshafts turn at the same speed.

Note, all 4 wheels DO NOT turn at the same speed. Not with the Torsen or with a part-time 4WD system. The only way all four wheels would turn at the same speed is if you had three locking differentials (front, center, and rear), and only a couple vehicles have that (Mercedes G500 and Wrangler Rubicon, IIRC).

See: Torsen General Frequently Asked Questions page
Torsen - Wikipedia, the free encyclopedia

When Im in 2wd the fornt driveshaft is dissengaged? correct?

Thanks for the info gang, Im surprised anyone would NOT want equal power transmit to front and rear axles in 4wd, seems like a waste to me to put a diff in that case unless you have an AWD vehicle. I guess Im old school in that respect. Oh and my IH Scout has locking diffs Dana 60 up fornt and a Dana 70 outback :bigok:

 

[Ross]

I have another question. Some limited slip or all wheel drive system will use some sort of disc that will lock when a slip is detected. With the Jeeps all wheel drive system, at least in years past, when a slip was detected the friction would heat up pads and they would absorb more fluid allow the differential to lock, but over time these disc wore and became less effective. Is this the case with the "all wheel drive" system in the 4th generation 4Runner? When you lock it what is locking, pads, gears, a chain?

 

[scottm]

The only way all four wheels would turn at the same speed is if you had three locking differentials (front, center, and rear), and only a couple vehicles have that (Mercedes G500 and Wrangler Rubicon, IIRC).

And '91-'97 80-series Land Cruiser.

When Im in 2wd the fornt driveshaft is dissengaged? correct?

Correct, and the center diff has to lock for power to go only to the rear in that case.

Thanks for the info gang, Im surprised anyone would NOT want equal power transmit to front and rear axles in 4wd, seems like a waste to me to put a diff in that case unless you have an AWD vehicle. I guess Im old school in that respect. Oh and my IH Scout has locking diffs Dana 60 up fornt and a Dana 70 outback :bigok:

It's nice to have AWD and 4WD options. Are those locking axles stock on your Scout?

 

[Jerrydog]

It's nice to have AWD and 4WD options. Are those locking axles stock on your Scout?

Oh hell no! custom built to fit the Scout only thing left is rear wheel disc brakes for it.

 

[galactic_04]

Oh hell no! custom built to fit the Scout only thing left is rear wheel disc brakes for it.

Make sure you don't go too big on those discs. We have chevy S10 disc brakes on the back of the 89 4runner and they ALWAYS grab before the fronts. It's a small disc, but you can't bias it enough toward the fronts. Makes for some killer E-brake style slides though!

 

[DocMT]

I have another question. Some limited slip or all wheel drive system will use some sort of disc that will lock when a slip is detected. With the Jeeps all wheel drive system, at least in years past, when a slip was detected the friction would heat up pads and they would absorb more fluid allow the differential to lock, but over time these disc wore and became less effective. Is this the case with the "all wheel drive" system in the 4th generation 4Runner? When you lock it what is locking, pads, gears, a chain?

Look up "Torsen" (stand for "torque sensing") differentials and you'll find all the answers.

 

[DocMT]

... Im surprised anyone would NOT want equal power transmit to front and rear axles in 4wd, seems like a waste to me to put a diff in that case unless you have an AWD vehicle. ...

But that's the beauty of our 4wd systems. We can treat it like AWD or we can treat it like a conventional part-time transfer case 4wd system. I like having the option for both, especially when I'm driving on partially snow-covered roads.

 

[Ross]

Look up "Torsen" (stand for "torque sensing") differentials and you'll find all the answers.

It use a planetary gear sets, seems to be a good system. With this type of diff in an axle you can help it by using your brakes. Other than locking the center diff (Transfer Case) is there any way you can help it gain traction?

The reason I am asking this is because I am used to more mechanical systems where when you put your selector in 4 wheel drive it engages almost instantly. I am also used to air lockers where they too can be engaged with a moment’s notice.

From what I am finding about my 4Runner is that I will need to switch the transfer case into the desired position well enough ahead of the time I may actually need added traction or gearing.

 

[DocMT]

It use a planetary gear sets, seems to be a good system. With this type of diff in an axle you can help it by using your brakes. Other than locking the center diff (Transfer Case) is there any way you can help it gain traction?

The reason I am asking this is because I am used to more mechanical systems where when you put your selector in 4 wheel drive it engages almost instantly. I am also used to air lockers where they too can be engaged with a moment’s notice.

From what I am finding about my 4Runner is that I will need to switch the transfer case into the desired position well enough ahead of the time I may actually need added traction or gearing.

You can drive your 4Runner in 4HI in any conditions because your transfer case has a center differential that allows different speeds without binding. So to say that you have to switch the transfer case before you need traction isn't really true. And if you find yourself in a really low-traction situation, you can always lock the differential.

 

[Ross]

You can drive your 4Runner in 4HI in any conditions because your transfer case has a center differential that allows different speeds without binding. So to say that you have to switch the transfer case before you need traction isn't really true. And if you find yourself in a really low-traction situation, you can always lock the differential.

When you lock the center and or shift into 4lo is it supposed be instant? Mine seems to have a little lag time.

Sorry for all the questions, I am not new to off roading but the 4Runner is new to me. I like to understand how the systems work. I live in a rural area and all wheel drive is need often, esp. winter.

I have a built Jeep that I use for everything from off roading to dragging trees or hauling live stock out of a muddy field. It would be nice to have a vehicle that was somewhat capable off road that has the comfort of the 4Runner.

 

[Doozi]

From what I am finding about my 4Runner is that I will need to switch the transfer case into the desired position well enough ahead of the time I may actually need added traction or gearing.

The beauty of the 4Runner's transfer case is that you can run in AWD mode (H4, unlocked) all the time and be ready. Are you referring to off-roading or driving in bad weather?

Remember that you should cycle the actuators regularly to provide smooth and consistent operation. When I first got mine with 67k miles on it, it would take several seconds to go just from H2 to H4, but since I've owned it and have exercised the mechanisms, it seems to switch modes much quicker in all cases... H2<>H4, H4<>L4, and locking and unlocking the diff.

Coupled with the ATRAC, it really is a pretty competent and versatile system. I found this little clip on the 'net that seems pretty impressive to me...

--language advisory--
YouTube - 4Runner 4Wheeling

~Doozi

 

[DocMT]

When you lock the center and or shift into 4lo is it supposed be instant? Mine seems to have a little lag time.

Sorry for all the questions, I am not new to off roading but the 4Runner is new to me. I like to understand how the systems work. I live in a rural area and all wheel drive is need often, esp. winter.

I have a built Jeep that I use for everything from off roading to dragging trees or hauling live stock out of a muddy field. It would be nice to have a vehicle that was somewhat capable off road that has the comfort of the 4Runner.

On my 4Runner, the center diff seems to lock in 1 or 2 seconds. And for 4LO, you have to stop, select neutral, then engage low gear. So of course that takes more time. But what I'm saying is that you can run 4wd all the time if you want, so there wouldn't be any need to "plan ahead".

 

[Ross]

On my 4Runner, the center diff seems to lock in 1 or 2 seconds. And for 4LO, you have to stop, select neutral, then engage low gear. So of course that takes more time. But what I'm saying is that you can run 4wd all the time if you want, so there wouldn't be any need to "plan ahead".

My concern that sometimes space is tight and it is easier to maneuver in 2wd or the all wheel drive. If I am getting lined up for an obstacle, hooking or moving a trailer (in a less than Ideal location) I would like to be able to go from all wheel drive right to 4 lo and center locked (I understand I need to be stopped and be in neutral to go to 4 low) as soon as I rotate the lever, I don't want to have to move forward or backward to engage or lock the center.

I have had my 4Runner for couple weeks and from what I have experienced with mine is that sometimes you need to move a little forward or backwards to get the tcase to lock in. I am just wondering if that is normal for a 4Runner or if I have an issue that needs to be looked at?

 

[M1911]

I have had my 4Runner for couple weeks and from what I have experienced with mine is that sometimes you need to move a little forward or backwards to get the tcase to lock in. I am just wondering if that is normal for a 4Runner or if I have an issue that needs to be looked at?

Do your maneuvering in 4WD hi with the center diff unlocked. Yes, it sometimes takes a bit to get the center diff to lock, but it helps if you are in neutral.

 

[Ross]

Do your maneuvering in 4WD hi with the center diff unlocked. Yes, it sometimes takes a bit to get the center diff to lock, but it helps if you are in neutral.

If the tires are spinning and it engages could there be damage?

 

[M1911]

If the tires are spinning and it engages could there be damage?

You can lock the center diff while moving, so I'd say no.