Rear differential lock

tbounds02

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Nov 20, 2023
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22 tundra
It really bothers me why the rear diff lock is only operable in 4 low , my tundra was same way , I can lock center lock in 4 high .
Why is that ?
In mud some times I need the high speed tire speed and lock rear diff .
 
It really bothers me why the rear diff lock is only operable in 4 low , my tundra was same way , I can lock center lock in 4 high .
Why is that ?
In mud some times I need the high speed tire speed and lock rear diff .
Center lock is locking the driveshaft’s together. Rear lock is locking the rear axles together which is very hard on the axles. I’m sure it can be done but people would forget them locked in high range and blow out the axles. Perhaps that’s Toyotas reason, I really don’t know. I know that my 4Runner does good with A-trac, MTS and in certain situations better than rear locker. I’m pretty sure that the new lc all modes in mts can be utilized in 4h now. Hope this helps you.
 
User Manual Tundra:

"When using the rear differential lock system
Failure to observe the following precautions may result in an accident.
Do not lock the rear differential in the conditions other than above.
Do not lock the rear differential until the wheels have stopped spinning.
Do not drive over 5 mph (8 km/h) when the differential is locked.
Do not keep driving with the rear differential lock state"

"Operating tips
Be sure to stop the wheels before locking the differential.
Unlock the differential as soon as the vehicle moves out."
 
Center lock is locking the driveshaft’s together. Rear lock is locking the rear axles together which is very hard on the axles. I’m sure it can be done but people would forget them locked in high range and blow out the axles. Perhaps that’s Toyotas reason, I really don’t know. I know that my 4Runner does good with A-trac, MTS and in certain situations better than rear locker. I’m pretty sure that the new lc all modes in mts can be utilized in 4h now. Hope this helps you.
Are you saying if I select mud setting in drive modes I can lock rear diff in high range
 
Give me a Detroit Locker! No worrying about engaging/disengaging. :) But yes, A-trac is very effective, albeit not instantaneous as a locked differential is. There is disappointment that a front locker was not offered, but it may have exceeded the budget to incorporate.
 
Are you saying if I select mud setting in drive modes I can lock rear diff in high range
No I’m not saying that. I’m saying that in certain situations MTS, a-trac can give better results than rear diff lock.
 
Had the same problem with my 79 fj 40 when I installed a new wiring harness on my arb lockers they said it was a safety issue told them that’s how I like to run my system and when I brake an axle I have the choice hi /lo front or rear . Have to make it back to camp and put on my trailer. So what they did was show me how rewire the harness worked great but safety was the problem for them. Worked around it. All was good my son still is using it.
 
Has anyone used a 318 method wheel with 40+(open country LT 285/75/18 how much will it rub waiting for my Westcott order
 
In the Tacoma world there was the Grey wire mod which transferred to 4Runners (although the wire was a different colour), both accomplished rear lock in 4H. It was simply grounding a specific wire to get 4H rear lock with some weird warning lights on the dash. I'm sure that something similar is possible with the new LC. That said, you can generate reasonable wheel speed in 4L, so maybe a driver mod would work too.

When I first got my 4Runner with a rear locker I had the same concern but over the years I learned that the electronic LSD did a pretty good job without snapping rear axles in 4H and A-TRAC in lieu of a front locker was even better in 4L. But in all honesty I'm a snow guy not a mud guy so I'm no expert.
 
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So in the mud drive mode even is 4 H I have a limited slip diff in the rear? Just not a full lock , but when wheel spin in rear happens it will lock up in the rear in4 H ?
I thought it would just be one wheel only in the rear unless the rear diff was locked?
I don’t know for sure just asking .
 
So in the mud drive mode even is 4 H I have a limited slip diff in the rear? Just not a full lock , but when wheel spin in rear happens it will lock up in the rear in4 H ?
I thought it would just be one wheel only in the rear unless the rear diff was locked?
I don’t know for sure just asking .
It’s difficult to explain and I’m not the best person to explain it but a-trac will apply brake to the wheel with the least traction or greatest slip and apply power to wheels with better traction. There are good write ups about Toyota 4wd systems. Do a google search for a-trac, mts, and crawl control. It is pretty amazing what these systems can do compared to an ‘80’s 4x4. Lock rear diff was nice in my 4Runner but I would trade it for a-trac and mts all day long.
 
It’s difficult to explain and I’m not the best person to explain it but a-trac will apply brake to the wheel with the least traction or greatest slip and apply power to wheels with better traction. There are good write ups about Toyota 4wd systems. Do a google search for a-trac, mts, and crawl control. It is pretty amazing what these systems can do compared to an ‘80’s 4x4. Lock rear diff was nice in my 4Runner but I would trade it for a-trac and mts all day long.
I do not want to trade my purely mechanical AWD for all the electronic traction control gadgets in the world. If I cannot get through with the right tires, in low range with both center and rear differential locked it means I took the wrong way :rolleyes:.
 
I do not want to trade my purely mechanical AWD for all the electronic traction control gadgets in the world. If I cannot get through with the right tires, in low range with both center and rear differential locked it means I took the wrong way :rolleyes:.
That is your choice and I respect that. My choice is to have a more capable 4WD system than I had in the 80’s.
 
So in the mud drive mode even is 4 H I have a limited slip diff in the rear? Just not a full lock , but when wheel spin in rear happens it will lock up in the rear in4 H ?
I thought it would just be one wheel only in the rear unless the rear diff was locked?
I don’t know for sure just asking .
This is a good video that gets into how some of the traction control options work. You don't get the one wheel spinning freely unless you turn off traction control. You also don't even need to engage A-TRAC to get the brake based traction control on the rear.
 
I do not want to trade my purely mechanical AWD for all the electronic traction control gadgets in the world. If I cannot get through with the right tires, in low range with both center and rear differential locked it means I took the wrong way :rolleyes:.
One downside of these electronic traction aides is that they favour a slow and steady approach. In situations where you would like to just give er with momentum they don't work as well as they tend to slow you down.
 
Hands down Toyota's ability to be buried in sand (stuck) and drive out, is truly something to behold.
 
My rear diff lock does not want to get engaged unless the center is already locked (in 4LO). I was assuming the locks will have the ability to engage independently. Is this expected behavior?
 
Yea, I read that first. No mention of a dependency on the center lock. I was wondering if others are able to lock the rear without locking the center.
 
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