Trying to understand center diff. vs. rear vs. front lock (3 Viewers)

[grinchy]

Center diff lock used here for 40 miles of city street urban driving in 2-6 inches of heavy wet, PNW ice/snow/slush. It's an autoadd for me anytime these conditions are prevalent, and I never have any drama at all. I'd say boring but it was family dental cleaning day, so we had all aboard and no drama is exactly what is desired in that situation.
I started working the switching a couple weeks ago, and this was 15-20 cycles in during that period. Today engaged on a cold transfer case and disengaged when we got home, like a champ.

I also optioned in 2nd gear start, which is a nice addition in these conditions.

 

[manofthewoods]

Center diff lock used here for 40 miles of city street urban driving in 2-6 inches of heavy wet, PNW ice/snow/slush. It's an autoadd for me anytime these conditions are prevalent, and I never have any drama at all. I'd say boring but it was family dental cleaning day, so we had all aboard and no drama is exactly what is desired in that situation.
I started working the switching a couple weeks ago, and this was 15-20 cycles in during that period. Today engaged on a cold transfer case and disengaged when we got home, like a champ.

I also optioned in 2nd gear start, which is a nice addition in these conditions.

don't shoot the messenger...
Believe it or not leaving the CD UNlocked means the TORSEN gets to distribute power to the axle with the best traction, up to 70/30 if memory serves. Locking the CD negates the benefits of using the TORSEN's ability to work its magic and turns it into a conventional transfer case (fixed at 50/50 distribution). Realistically, in most instances it won't make a difference. The only concerns, minor in most cases, could be:
1) driveline windup if traction is good or,
2) on ice, having a wheel break loose because the adhesive capabilities of the tires on the axle are overtaken by the power given to that axle by the transfer case.

2nd start, exercising the CD lock and Low Range actuators - smart things to do.
Stay warm and happy holidays

 

[kcjaz]

don't shoot the messenger...
Believe it or not leaving the CD UNlocked means the TORSEN gets to distribute power to the axle with the best traction, up to 70/30 if memory serves. Locking the CD negates the benefits of using the TORSEN's ability to work its magic and turns it into a conventional transfer case (fixed at 50/50 distribution). Realistically, in most instances it won't make a difference. The only concerns, minor in most cases, could be:
1) driveline windup if traction is good or,
2) on ice, having a wheel break loose because the adhesive capabilities of the tires on the axle are overtaken by the power given to that axle by the transfer case.

2nd start, exercising the CD lock and Low Range actuators - smart things to do.
Stay warm and happy holidays

I wonder how effective it would be if the traction control automatically locked the CDL when it sensed the two front or two rear wheels have lost traction? Would that be any different than letting MTS or traction control it’s thing?

 

[bloc]

I wonder how effective it would be if the traction control automatically locked the CDL when it sensed the two front or two rear wheels have lost traction? Would that be any different than letting MTS or traction control it’s thing?

Engaging while there is a difference in speed is a good way to damage the collar that locks the two together.

 

[lx200inAR]

don't shoot the messenger...
Believe it or not leaving the CD UNlocked means the TORSEN gets to distribute power to the axle with the best traction, up to 70/30 if memory serves. Locking the CD negates the benefits of using the TORSEN's ability to work its magic and turns it into a conventional transfer case (fixed at 50/50 distribution). Realistically, in most instances it won't make a difference. The only concerns, minor in most cases, could be:
1) driveline windup if traction is good or,
2) on ice, having a wheel break loose because the adhesive capabilities of the tires on the axle are overtaken by the power given to that axle by the transfer case.

2nd start, exercising the CD lock and Low Range actuators - smart things to do.
Stay warm and happy holidays

You're leaving one piece of the puzzle out though and is the reason for the CDL. A torsen LSD, uses a torque multiplier design. So, if one wheel is fully spinning (little ot no torque applied), then the diff can't provide any torque to the other axle that has grip. Obviously, this is where ATRAC and Crawl come in to play to help, but without the brake control a vehicle with a Torsen diff would be stuck if just one wheel was spinning freely.

LINK

Downsides​

The car will not move with one of the wheels in the air. If one wheel is in the air or has no traction at all, it will only take very little torque to turn that wheel. It is necessary to apply torque to the gears to generate the required thrust force to maintain the bias ratio. Without torque, the gears will not be pressed together and no friction will be generated, so the gears can rotate freely. The unloaded wheel will have high speed, but can only transfer very little or no torque.

 

[manofthewoods]

You're leaving one piece of the puzzle out though and is the reason for the CDL. A torsen LSD, uses a torque multiplier design. So, if one wheel is fully spinning (little ot no torque applied), then the diff can't provide any torque to the other axle that has grip. Obviously, this is where ATRAC and Crawl come in to play to help, but without the brake control a vehicle with a Torsen diff would be stuck if just one wheel was spinning freely.

LINK

Downsides​

The car will not move with one of the wheels in the air. If one wheel is in the air or has no traction at all, it will only take very little torque to turn that wheel. It is necessary to apply torque to the gears to generate the required thrust force to maintain the bias ratio. Without torque, the gears will not be pressed together and no friction will be generated, so the gears can rotate freely. The unloaded wheel will have high speed, but can only transfer very little or no torque.

Fair enough, and I suspect that's why the engineers included the locking button.
In the scenario above of taking the kids to the dentist, assuming not off Road, likely, just driving in high range w/2nd gear start would yield the best overall traction.

 

[bloc]

You're leaving one piece of the puzzle out though and is the reason for the CDL. A torsen LSD, uses a torque multiplier design. So, if one wheel is fully spinning (little ot no torque applied), then the diff can't provide any torque to the other axle that has grip. Obviously, this is where ATRAC and Crawl come in to play to help, but without the brake control a vehicle with a Torsen diff would be stuck if just one wheel was spinning freely.

LINK

Downsides​

The car will not move with one of the wheels in the air. If one wheel is in the air or has no traction at all, it will only take very little torque to turn that wheel. It is necessary to apply torque to the gears to generate the required thrust force to maintain the bias ratio. Without torque, the gears will not be pressed together and no friction will be generated, so the gears can rotate freely. The unloaded wheel will have high speed, but can only transfer very little or no torque.

This is correct. My description was an oversimplification to make the point. With regard to the center diff and our atrac system it is very unlikely one tire will be completely without traction.

 

[JohnPW]

You're leaving one piece of the puzzle out though and is the reason for the CDL. A torsen LSD, uses a torque multiplier design. So, if one wheel is fully spinning (little ot no torque applied), then the diff can't provide any torque to the other axle that has grip. Obviously, this is where ATRAC and Crawl come in to play to help, but without the brake control a vehicle with a Torsen diff would be stuck if just one wheel was spinning freely.

LINK

Downsides​

The car will not move with one of the wheels in the air. If one wheel is in the air or has no traction at all, it will only take very little torque to turn that wheel. It is necessary to apply torque to the gears to generate the required thrust force to maintain the bias ratio. Without torque, the gears will not be pressed together and no friction will be generated, so the gears can rotate freely. The unloaded wheel will have high speed, but can only transfer very little or no torque

You're leaving one piece of the puzzle out though and is the reason for the CDL. A torsen LSD, uses a torque multiplier design. So, if one wheel is fully spinning (little ot no torque applied), then the diff can't provide any torque to the other axle that has grip. Obviously, this is where ATRAC and Crawl come in to play to help, but without the brake control a vehicle with a Torsen diff would be stuck if just one wheel was spinning freely.

LINK

Downsides​

The car will not move with one of the wheels in the air. If one wheel is in the air or has no traction at all, it will only take very little torque to turn that wheel. It is necessary to apply torque to the gears to generate the required thrust force to maintain the bias ratio. Without torque, the gears will not be pressed together and no friction will be generated, so the gears can rotate freely. The unloaded wheel will have high speed, but can only transfer very little or no torque.

Yes but won’t the spinning wheel automatically have brake applied, via traction control and/or ATRAC, to prevent this from ever happening on a 200? The video with the 4runner with ATRAC off demonstrates what an open diff will do with spinning wheels…but I thought the traction control/braking to prevent this was automatic on our 200’s, without having to engage CRAWL, or anything else. Am I wrong on this?

 

[Mrtwooooo]

I know this is a GX video but about 14:00 minutes in the guy starts climbing a muddy snow covered hill. 4Lo with the CDL unlocked. At 24:50 he’s realizing he forgot to lock the CDL and suddenly he starts making better progress.

 

[grinchy]

don't shoot the messenger...
Believe it or not leaving the CD UNlocked means the TORSEN gets to distribute power to the axle with the best traction, up to 70/30 if memory serves. Locking the CD negates the benefits of using the TORSEN's ability to work its magic and turns it into a conventional transfer case (fixed at 50/50 distribution). Realistically, in most instances it won't make a difference. The only concerns, minor in most cases, could be:
1) driveline windup if traction is good or,
2) on ice, having a wheel break loose because the adhesive capabilities of the tires on the axle are overtaken by the power given to that axle by the transfer case.

2nd start, exercising the CD lock and Low Range actuators - smart things to do.
Stay warm and happy holidays

no worries. at least I didn't decide to kick the rear elocker in

While conditions were not extreme (IMO, but I lived in the midwest), we saw plenty of rear drive sports cars (Cadillac V, BMW 4s, etc) who could no longer make progress and had gone into hazard light mode. We also saw a few front drive, compact SUVs unable to maintain lane very well and thus having to go less than 10 mph.

I can only speak to what it feels like behind the wheel, for me. CDL unlocked feels a tiny bit squirrelly. Like slip is just around the corner. When it feels like that, I lock in the CDL and immediately get 'tank like' traction. By which I mean the rig feels locked in the direction of travel. As long as I maintain a speed that doesn't require wheel slip (heavy braking, heavy acceleration), and I'm not adding a lot of corner G, I'm going to get where I'm going, under control. Love the feeling and will be optioning it every time.

Obviously on a 20 mile one way interurban trek you can't avoid every hill, though I tried to drive a route which had as little slope as possible (and also as little other traffic as possible,) though some 4 and 6 lane 35 mph road was inevitable, those were getting ridiculous and we left them for the more slippery, but less dangerous side streets ASAP. I am always pleased with the LX going up slippery hills, it is just inevitable.

I did find an empty iced up parking lot a few years ago and did some donuts in all the modes to get a feel for the rig. One mode was markedly easier to spin than the other, but I don't recall if it was CDL in or out . . . a repeat of this empirical research may be required.

 

[manofthewoods]

One mode was markedly easier to spin than the other, but I don't recall if it was CDL in or out . . . a repeat of this empirical research may be required.

A full report (signed by the governor, of course) shall be due on the MUD desk before Christmas! Bonus MUD points if you have video

I would do it myself, but I'm presently cloistered in traction abundant central CA. - I did take my '19 LC through a juicy Sierra (shutdown I80 type) blizzard 2 years ago and found it to be awesome w/stock tires, and I too did on occasion lock the CD (in retrospect, I didn't really notice any difference, however).

enjoy the kids, your time with them will seem fleeting indeed.

 

[lx200inAR]

Sorry, i wasn't trying to say anyone should do anything different. Just wanted to add that piece of the puzzle for anyone following along as a data point. Personally, I'd rather rely on a locked CDL in high slip scenarios than waiting for the brakes to bail me out. If we are talking medium to low slip scenarios, then I would just rely in ATRAC. Ill caveat the above with I don't have a ton of off -road / snow and ice driving experience, so that's just going on what "feels right" in my brain.

 

[TeCKis300]

One mode was markedly easier to spin than the other, but I don't recall if it was CDL in or out . . . a repeat of this empirical research may be required.

That would be CDL in. As it also conveniently turns off traction control for some hooning fun. 4 wheel drifts in parking lots...weee. Wife not impressed.

Actually to that point, I think both you and @manofthewoods are right. Really depends on the type of snow/ice on the roads as to which mode may be advantageous. Having CDL unlocked allows stability and traction control safety nets to continue to "help". It also allows the tires to better track in turns, eeking out potentially more corning traction (in compatible conditions). Whereas CDL lock will force the front and rear axles to rotate 1:1 and forcing slip in corners. Yet to your point, there maybe conditions already so slippery that having CDL engaged is more positive.

 

[grinchy]

might be interesting to try the donuts with VSC off and CDL off.

 

[TeCKis300]

I think they are just mining the forum at this point.

Still surprised the Taco couldn't sort this test. The earlier gen 100-series with ATRAC could handle this, and I have no doubt the 200-series ATRAC could do it as well. Maybe the Taco system is different or it has to be engaged in some way?

 

[TeCKis300]

might be interesting to try the donuts with VSC off and CDL off.

Doable, but not as easy. Power on oversteer is harder as power is routed to the tire with least traction, and breaks traction for 1 tire. Whereas with the center locker in, it's easier to break traction with more tires.

Just like drifting a RWD car, it's easier to do with an LSD or spool, versus an open diff. That fact is probably not very relatable. But it's even easier if one has a rear locker or all lockers in.

 

[kcjaz]

Fair enough, and I suspect that's why the engineers included the locking button.
In the scenario above of taking the kids to the dentist, assuming not off Road, likely, just driving in high range w/2nd gear start would yield the best overall traction.

is there some automatic mode for "2nd gear start"? The only 2nd steer start I know about is manual (easy enough, don't really need some setting to lock out 1st gear, just curious). I may be doing more of that on ice with my new 4.88s installed.

One thing I have always loved about my LC on starts after a full stop at an icy intersection is that it goes straight with now fish tail. I may be spinning somewhat but I'm going straght.

 

[kcjaz]

Engaging while there is a difference in speed is a good way to damage the collar that locks the two together.

good point.

 

[manofthewoods]

is there some automatic mode for "2nd gear start"? The only 2nd steer start I know about is manual (easy enough, don't really need some setting to lock out 1st gear, just curious). I may be doing more of that on ice with my new 4.88s installed.

One thing I have always loved about my LC on starts after a full stop at an icy intersection is that it goes straight with now fish tail. I may be spinning somewhat but I'm going straght.

I don't know about your year vehicle but mine has a button for 2nd gear start by the shifter. My '97 LX450 even has it.

 

[kcjaz]

I don't know about your year vehicle but mine has a button for 2nd gear start by the shifter. My '97 LX450 even has it.

you mean this thing?

LOL. I've only owned my 200 for 7 years. Haven't had a chance to figure it all out yet... I'm going to go out and look for all the other buttons I no longer see or have never used. Next your going to tell me I have 4LO...