Center Differential Locker-Hi vs. Low?

[Blue Sky]

I am familiar with hi/low and lockers but center differentials are confusing to me.

I understand that it is a 50/50 F/R lock but....

When do I use it in High vs Low gear?

*Edit-When have you used the center differential lock in high gear? What were the conditions and why?

 

[APIOQM]

I think you have to be in low-range to use either of the lockers. The advantage to leaving the differentials unlocked in low-range is improved turning radius and less scrubbing. In my mind, unless you’re on very technical terrain where traction is an issue, you don’t really need to use the differential locks. The Torsen differential and traction control (ATRAC with crawl control) is adequate for all other scenarios.

 

[LCOceans]

Pretty sure you can use center locker in either hi or low. Can use center at speeds up to 62mph or it will automatically shut off. Rear locker must be in 4Lo which means you must not exceed about 17 mph if I recall correctly. We do not have a front locker. Only center and rear. Our traction control system sort of serves as a front locker. Hope this helps.

 

[jpto]

IMO the center locker switches your GX from a smart AWD old school 4WD. The only time you'd want to lock your center diff in high is when you're expecting the front axles and rear axles to suddenly have different levels of traction, i.e. icy surfaces, running on a mix of gravel/dirt and need power evenly distributed.

I haven't locked my center diff in high but on older systems when you engaged the center locker ABS would turn off, this is useful on in the snow/ice when you want to lock up the wheels a bit to stop faster vs ABS (counter intuitive but it's a thing on snow covered ice surfaces)

 

[JustinHEMI]

Page 438.

https://www.landcruiserforum.com/manuals/2024-toyota-landcruiser/OM60U35U.pdf

Some wrong info already posted.

 

[LCOceans]

The good ol manual is the way to go.

 

[Captain Trips]

Page 438.

https://www.landcruiserforum.com/manuals/2024-toyota-landcruiser/OM60U35U.pdf

Some wrong info already posted.

Wow! There’s a manual that describes everything about this vehicle? Then why are there so many questions about the vehicle?

 

[gregh]

For those not familiar with locking differentials. Pay attention to these rules or you could leave parts of your drivetrain on the ground or severely damage it.

NOTICE
To prevent damage to the center differential
● For normal driving on dry and hard surface roads, unlock the center differential.
● Unlock the center differential after the wheels are out of the ditch or off the slippery or bumpy surface.
● Do not push the center differential lock switch when the vehicle is turning or when its wheels are spinning freely off the ground

Why?
During a turn each wheel is traveling a different arc with different radius. The distance each wheel travels is a function of the radius (2πr). The wheels rotate at different speeds to cover the different distances of their unique arcs of travel as them move in unison. With differentials locked, the wheels are forced to rotate at the same speed. i.e. they're all trying to go the exact same distance.

On a soft surfaces tires can slip an spin allowing wheel rotation to match. On hard surfaces, or anywhere you have good traction, the drivetrain is fighting the grip of the tires. It can lead to driveline windup which can prevent the differentials from unlocking and the transmission from shifting gears. Or stuff breaks.

 

[TakaraLC]

Since center diff is a torsen (not an open diff), it will actually perform adequately for 90% of conditions even when unlocked. It is vastly superior to the open transfer-case on Tacoma and 4runner.

If you are rock crawling, locking center will help, since torsen diffs will have trouble if one axel completely loses traction (i.e. if a tire lifts off ground) since torsen function by vectoring and multiplying torque going from axel with least traction to the axel with more traction. The amount vectored is determined by torsen torque bias, which usually is around 4X, meaning 4X the amount of torque the low traction axel has is sent to the axel with more traction. If least traction is equal to zero, 4 times zero is still zero. Traction control can help with this by applying the breaks and artificially generating resistance for torsen to vector back. But this will cause strong "kickback" effect, which probably would make control difficult during rock crawling.

Below is a video showing how torsen operates. I believe this is an older variant (Torsen type-A). I suspect we have a torsen type-C, which is different but operates based on the same principles.

 

[Jamin55]

For those not familiar with locking differentials. Pay attention to these rules or you could leave parts of your drivetrain on the ground or severely damage it.



Why?
During a turn each wheel is traveling a different arc with different radius. The distance each wheel travels is a function of the radius (2πr). So the wheels rotate at different speeds. With differentials locked, the wheels forced to rotate at the same speed. i.e. they're all trying to go the exact same distance.
View attachment 31075
On a soft surfaces tires can slip an spin allowing wheel rotation to match. On hard surfaces, or anywhere you have good traction, the drivetrain is fighting the grip of the tires. It can lead to driveline windup which can prevent the differentials from unlocking and the transmission from shifting gears. Or stuff breaks.

Good explanation, for those who have been 4 wheeling and have or had jeeps and their systems know to never lock them on hard surfaces. Sometimes dry can have loose dirt, gravel etc.

 

[gregh]

Good explanation, for those who have been 4 wheeling and have or had jeeps and their systems know to never lock them on hard surfaces. Sometimes dry can have loose dirt, gravel etc.

I suspect everyone in the 4x4 community has heard at least one story of a Salesman not familiar with that rule locking the differentials in the paved parking lot during a test drive and leaving parts of the drivetrain on the pavement.

The one I heard was a Jeep Rubicon.

 

[jbe2289]

as already said, you can lock the center differential in hi or low, while the rear only in low. You should lock the center differential when, and only when, you are on slippery or lose surfaces: snow, ice, dirt, gravel. You also should always lock the center differential for prolonged driving on these surfaces to save the center differential from needing to do a lot of work and potentially being damaged. The only time to use the rear locker is if you are tackling something really challenging or might get stuck: steep rutted out climb, mud pit, rock crawling.

 

[Blue Sky]

Wow. After reading the scatter-shot of answers, I realized my initial question was overly vague. Sorry about that. However, there is a ton of useful information in these responses! Thank You!

The question I had about the high/low center diff. usage arose when I was reading about it in the manual. I understand locking the center diff in Low gear scenarios.

However, as pointed out, the Torsen diff. with A-trac will be more than adequate in most cases. While locking the center diff. in low will pick up the remaining reasons for using this feature.

What was also pointed is that incorrect use of the locking diff. feature could do serious damage the our LC's.

And yet I cannot come up with more than one reason to use the center diff. lock in high while say driving 30-60 mph? Admittedly, I have almost not experience driving in extended sandy scenarios, so maybe this would be a use case?

I am going to rephrase the initial question and add an edit.

When have you used the center differential lock in high gear? What were the conditions and why?

 

[TheBat]

I use the center diff lock on icy highways. Even a little slip from the torsen can put you sideways. People often talk about not using the center lock over 60 mph which is not correct. On the highway slow down to below 60, engage the center lock, then carry on at speeds above 60 if conditions allow. Think about it as no different than using 4H in a part-time 4wd, you don't see 4Runners limiting speed to 60 or driving in 2H in the winter.

 

[TakaraLC]

I use the center diff lock on icy highways. Even a little slip from the torsen can put you sideways. People often talk about not using the center lock over 60 mph which is not correct. On the highway slow down to below 60, engage the center lock, then carry on at speeds above 60 if conditions allow. Think about it as no different than using 4H in a part-time 4wd, you don't see 4Runners limiting speed to 60 or driving in 2H in the winter.

Yeah 60MPH thing is only for engaging and disengaging. It wont let you got from locked to unlocked, or vice versa, above 60 MPH.

 

[TakaraLC]

as already said, you can lock the center differential in hi or low, while the rear only in low. You should lock the center differential when, and only when, you are on slippery or lose surfaces: snow, ice, dirt, gravel. You also should always lock the center differential for prolonged driving on these surfaces to save the center differential from needing to do a lot of work and potentially being damaged. The only time to use the rear locker is if you are tackling something really challenging or might get stuck: steep rutted out climb, mud pit, rock crawling.

A torsen diff will not get damaged or overworked. Torsen is not a clutch based limited slip diff. Plus, when a torsen diff is locked, the same internal gears are still spinning, it just doesn’t allow speed difference between the output shaft gears.

 

[gregh]

Good explanation, for those who have been 4 wheeling and have or had jeeps and their systems know to never lock them on hard surfaces. Sometimes dry can have loose dirt, gravel etc.

Rereading it, I did try to clarify some things.

 

[Blue Sky]

I use the center diff lock on icy highways. Even a little slip from the torsen can put you sideways. People often talk about not using the center lock over 60 mph which is not correct. On the highway slow down to below 60, engage the center lock, then carry on at speeds above 60 if conditions allow. Think about it as no different than using 4H in a part-time 4wd, you don't see 4Runners limiting speed to 60 or driving in 2H in the winter.

Interesting. And very helpful thinking of the center diff lock in terms of a traditional 4wd system. Most 4runners and tacomas need 4H because they are run predominantly as a RWD vehicle.

Maybe I got it wrong, but one of the biggest selling features for me was the full-time 4wd (AWD) which I thought would be preferred (superior) to a traditional 4WD/4H driving in higher speed, inclement conditions.

I've owned quite a few AWD and 4WD vehicles over the years, but the LC is first vehicle I've owned where it can be/do both. Maybe I can have it both ways? Looking forward trying the center diff lock when we get our next winter storm.

 

[gregh]

When have you used the center differential lock in high gear? What were the conditions and why?

I use the center diff lock on icy highways. Even a little slip from the torsen can put you sideways. People often talk about not using the center lock over 60 mph which is not correct. On the highway slow down to below 60, engage the center lock, then carry on at speeds above 60 if conditions allow. Think about it as no different than using 4H in a part-time 4wd, you don't see 4Runners limiting speed to 60 or driving in 2H in the winter.

Pretty much this and I was typing something similar.

I used the center diff on snow and ice on the GX470 because it forces a 50/50 power and braking force distribution.

 

[ultane]

Since center diff is a torsen (not an open diff), it will actually perform adequately for 90% of conditions even when unlocked. It is vastly superior to the open transfer-case on Tacoma and 4runner.

If you are rock crawling, locking center will help, since torsen diffs will have trouble if one axel completely loses traction (i.e. if a tire lifts off ground) since torsen function by vectoring and multiplying torque going from axel with least traction to the axel with more traction. The amount vectored is determined by torsen torque bias, which usually is around 4X, meaning 4X the amount of torque the low traction axel has is sent to the axel with more traction. If least traction is equal to zero, 4 times zero is still zero. Traction control can help with this by applying the breaks and artificially generating resistance for torsen to vector back. But this will cause strong "kickback" effect, which probably would make control difficult during rock crawling.

Below is a video showing how torsen operates. I believe this is an older variant (Torsen type-A). I suspect we have a torsen type-C, which is different but operates based on the same principles.

What a great video. Imadufus, and even I can understand it!