Crawl control made a fan out of me...

I think it would have been a better experiment if you had tried the same obstacle without the locker engaged, ie crawl control only. I’m also not sure why you used crawl control as opposed to multi-terrain select in that situation. I don’t have crawl control because I have the 6MT (but I do have ATRAC), but my understanding of crawl control leads me to believe it is best for crawling slowly over rocks and other such obstacles where maintaining a constant slow speed is otherwise difficult.

 

Wha? I’ve never found the locker to decrease my traction, but it does make turning more difficult. The most frequent reason I don’t use it is because I’m too lazy to wait for it to engage.

 

The locker is good for moguls and articulation where one wheel is going to hang or have very little weight and just spin. CC mitigates this with the ABS system like A Trac, but a locker physically locks the two wheels together so they can't spin independent. Thus why it hinders CC and you now have traction. In normal off roading, you'll likely never need it.

 

I know how the locker and traction control work and have also used them extensively. In many situations the locker plus traction control isn’t any better than traction control alone , but sometimes it definitely is. I see no reason to engage the locker without traction control also on. In that mode traction control provides a pseudo front locker in addition to the real rear locker.

 

Specifically with crawl control though, it's a bit redundant to use both. Given that CC works by braking individual wheels you're taking away 50% of it's ability to operate by locking the rear wheels together.

 

I’m still not following you. ATRAC also works by using the ABS brakes to limit uneven wheel spin, but it is completely redundant on the rear axle when you have the locker engaged because the locker is superior. However, when the locker is engaged and traction control is on, you have the most aggressive mode possible on our trucks unless you install a front locker.

i also think that traction control works best it situations where you cannot avoid wheel spin (eg mud and snow) . It’s downsides due to it being a reactive system are not a big deal. However, in situations where wheel spin is a bad idea (eg rock crawling) the locker shines.

 

We are taking about crawl control in the other thread and I think I might now understand where you are coming from. Although both ATRAC and CC both use the ABS brakes to limit uneven wheel spin, CC also uses the ABS brakes to maintain a constant speed (ie slow it down when required) and that aspect might be hindered by having the ABS brakes disabled on the rear axle.

 

I'm not talking about TC, I'm talking about CC.

If you activate CC, it is using ABS to apply brakes to each wheel, as needed, to optimize traction. If you turn on your locker and use CC, you're basically not allowing CC to independently control each rear wheel because essentially it is braking both wheels at the same time even though it may be only trying to apply it to one.

 

never tried using the lockers and CC at the same time; wouldnt the control unit be programmed to disable or compensate? Sounds like two opposing forces trying to accomplish some but workin against one another.

 

I think we are talking past each other.

In my world view, crawl control, multi-terrain select, ATRAC, TRAC, and Auto LSD are all forms of traction control. All of them use the ABS brakes to “optimize traction” by limiting uneven wheel spin.

Uneven wheel spin occurs when a wheel has less traction than the wheel on the other side of the axle (e.g. one wheel off the ground). Traction control applies the ABS brakes to the wheel with less traction (the one off the ground) which in turn causes more torque to go to the wheel with more traction (the one on the ground). Please correct me if you think any of the of this is not incorrect. I’m not an automotive engineer. I’m just a random guy on the internet.

While these systems are much better than open diffs, they are not as good as a differential locker. A diff locker prevents uneven spin from ever occurring in the first place. So if we are talking solely about optimizing traction, a diff locker cannot degrade the performance of a traction control system. It can only enhance it.

That said, crawl control does more than optimize traction. It also attempts to maintain a constant speed and it is this function that might be hampered by a locking differential. See my other post.

Am I making sense now?

 

AFAIK, locking the rear diff disables the ABS brakes on the rear but not on the front. As far as preventing uneven wheel spin, the rear ABS brakes aren’t needed when the rear diff is locked because uneven wheel spin is impossible in that situation. Even if the ABS brakes were enabled, traction control would never activate them because uneven wheel spin would never occur.

That said, crawl control does more than limit uneven wheel spin and that function might be hindered by the rear locker. See my other posts.

 

Went out to the truck and selected 4lo, engaged the rear locker and turned on crawl control and truck just moved along as usual with the abs pump cycling like crazy on the gravel. Turned off crawl control and had no difference in movements etc but Crawl with lock works so they must compliment each other as mentioned above.

As for the ABS pump controlling the rear brakes if the locker is enabled is a good question.

Think that is a great discussion so far.

https://www.autotrader.com/car-news/toyota-tacoma-trd-pro-road-feature-review-281474979875888
Mentioned:
2-Wheel Drive
Not so much a feature as it is a fun maximizer, but I did the majority of my driving with only the rear axle engaged.

Traction Control — Press vs. Press and Hold
To take things one step further in 2-wheel drive, turning off traction control with a button on the overhead console meant sideways fun. Only after my time with the TRD Pro was over did I learn that this is a two-step system on the Tacoma. A quick press-and-release of the button only restricts traction control. Press and hold the button for a few seconds turns it off completely.

4-Wheel Drive – High-Range
I used 4-high when I was anticipating rough stuff ahead, as it offers a little more stability and sure-footedness when rocks and uneven surfaces start to emerge on the trail. On the Tacoma, it can be engaged on the fly, meaning there’s no need to stop and shift to neutral. This enabled me to flip it on and off quickly.

4-Wheel Drive – Low-Range
Whenever the need for a bit of rock-crawling presented itself, it was time for 4-low. Think of driving over a bunch of picnic tables or up a staircase. Engaging 4-low requires the vehicle to be stopped and the transmission to be in neutral. Once engaged, the vehicle crawls along at a much slower pace, due to the low gearing of the transfer case — and it allows the vehicle to grind and wind up and over rocks and boulders. 4-low is for the rough stuff.

Locking Rear Differential
Vehicles utilize "open" differentials, which are designed to send power to whichever wheel has the least traction. The need for each wheel to turn at a different speed is rooted in basic geometry: when the car is turning, the wheel on the outside travels slightly further than the wheel on the inside. Therefore, leaving the differential "open" allows each wheel to cover a different distance, which in turn makes for better handling. With the differential "locked," the wheels travel at the exact same speed — not great for handling, but awesome for churning along over uneven terrain with the wheels pointed straight ahead.

In the Tacoma, I’d lock the rear diff anytime I was in 4-low and facing an especially tricky obstacle. Once I got over it, I’d disengage the rear locker in order to regain maneuverability and minimize stress on the components.

Crawl Control
Crawl Control can be viewed as an off-road cruise control system. It’s operated with a button and dial mounted in the overhead console, and it utilizes the brakes, ABS and throttle to guide the Tacoma up hills, down hills and along rocks and uneven terrain in the calmest manner possible. It doesn’t sound gentle, though, as all of these components creak and rattle from underneath the vehicle as the system is at work. Where Crawl Control especially shines is in getting the vehicle unstuck from deep mud or sand dunes — and there are some great video of this in action online.

And in case you were wondering — Crawl Control also works in reverse.

Multi-Terrain Select
Multi-Terrain Select is similar to Crawl Control, but it relies primarily on the Tacoma’s Active Traction Control system (A-TRAC) to optimize traction over various surfaces. It has four different modes: mud/sand/dirt, loose rock, moguls and rock. In Moab, I found myself slipping as I tried to climb up an uneven slickrock incline. I engaged rock mode on the multi-terrain select dial, and I was surprised at how, after searching for traction for a moment, the Tacoma climbed up the rock embankment with ease.


Found this post on overlandbound: /forums/threads/open-differentials-vs-traction-control-vs-lockers.22277/

 

We're on the same page. My only point is that if the ABS system is applying brakes to, say, the right rear; with the locker engaged it is in turn also braking the left wheel instead of allowing it to spin like it is trying to do. I'm not saying there's no need for a locker, but you do not need to use it when also using CC.

 

I think you have it backwards. Traction control and a locker are trying to solve the same problem, but the locker is better at it than traction control; not the other way around.

As I think you might be trying to say, the rear locker interferes with turning unlike traction control. It will cause wheel spin and binding when turning.

 

Yes, that is correct. But I think you're missing what I'm saying. Even Toyota says you don't need to use the locker when using CC. The locker will likely be stronger, yes, but again, if anything, it is sort of defeating the purpose of CC.

 

Traction control that works across the axle will never sense wheel slip left to right with the diff locked and therefore won't attempt to ever brake one wheel. Having said that, the system in the Tacoma knows the rear diff is locked and therefore will cease electronic control across the rear left to right anyway. The locker will always maximize torque that reaches the ground whereas a brake based traction control system cannot.

You nailed everything. I would say CC is not traction control though. It does maintain traction control functionality when it is activated, but that is really your MTS operating simultaneously with the CC function. The unique feature CC extracts is the cruise control maintaining a set speed.

 

It isn't. The locker works in addition to CC. CC with rear locked will run MTS (a form of A-TRAC) across the front and maintain a set speed while your rear will be automatically utilizing all traction available up to the traction limit which in this case is the total of both rear tires. CC may apply the brakes at the rear but that's only to maintain speed, not to aid as a traction device.

 

This would be a concern for vehicle stability control if the truck wanted to fire a single brake and didn't know an axle was locked. But in normal operation for traction control the system will never sense across axle wheel slip and thus wouldn't try and brake a single wheel. Now if it tried to brake the rear based on both tires slipping relative to a front tire with zero velocity, yes it would cause both rear wheels to brake, but this is exactly what you'd want the corrective action to do in this case.

Yes, there will be cases where a rear locker is needed with CC. Again, the rear locker will always be able to maximize the use of all available rear grip whereas CC with MTS/A-TRAC cannot.

 

This thread certainly makes the argument for buying an OR instead of a Sport hahaha

 

I turned it all on because I was under the impression that the system was designed to work together and that any system working against another would automatically cancel itself out.

All I know is that once I got underway all I had to do was concentrate on steering my way up the best - or as in this case really - the only line available, which was critical to get right the first time because a couple inches to either side would’ve resulted in calamity. I wasn’t gonna get a do-over had I lost traction, fell in a rut, or flipped the truck.

I walked it first to make sure I had the proper line picked out then got back in and started out in the first setting to go down and over the steep embankments of the wash at the base. I then switched between one, two, and three as I eased my way up the rest. Truck never broke traction or slipped. I was amazed.