Center Diff Lock - Educate me please

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uHu said:
Well, this test was done MANY years ago by the leading Auto-magazines of the Nordic contries (Norway, Sweden and Finland, at least), on snowy winter roads. Partly deep snow (for beeing a public road). Don't think the report is available on the net. What I remember is the conclusion, that the Toyota Tercel Wagon 4WD, with the simplest system in the test, and maybe cheapest to, came out best in stability, handling, acceleration and maybe braking. The cars where small family cars, and some were more than twice the cost of the Tercel. The basis for the success of the simple 4wd system (locked or no CD) is that the front and rear axles are forced to move at the same speed, which is an advantage when going more or less straight on slippery surfaces.
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Yes....in MOST situations. Having any diff locked, incl the center causes driveline settling when turning and can throw you into a skid, especially on ice. This is where an open (incl CDL) TRAC-equipped rig has the huge advantage. If the snow get's deep you can lock your CDL for even more traction though as some risk of skid if on ice. My 100 is so far improved over my 80's in these areas it's hilarious.
 
ShottsUZJ100 said:
You mention a 1999 model year? Just note that a 98-99 100-series takes a big step back in these slippery conditions to a 2000+ model year due to A-TRAC and VSC. No comparison in capability.
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I have to agree fully John.

TRAC is SO capable when running in snow, ice or many other poor traction surfaces, that it makes driving in these situations almost TOO easy !

Sunday I was doing some LIGHT wheeling on fresh snow in the mountains...I came to a dropoff both into and out of a wash, where one of the front and one of the rear tires were in a semi-blocked position on small icy berms.

Even with the CDL unlocked, the TRAC system seamlessly started gently pumping the brakes on the two "stuck" tires, giving the two free or "open" tires a larger portion of the engine`s power.

My 100 hesitated for only a moment before my forward momentem was restored and I was on my way.

A traditional ( No TRAC / w open diffs ) 4Runner came through behind me, and those same two tires that were resting against the bumps spun helplessly...He couldnt move forward OR backward..he was stuck..

Ive been in NUMEROUS situations where a Part-time 4x4 without TRAC has been stopped by only two, or even only ONE tire with resistance against it, You just wont have that happen with TRAC..Even with the CDL disengaged !

BUT..

I normally engage my CDL only when I really think that TRAC alone wont be enough to pull me through. I run an open center diff most of the time, but even more-so when running trails with real tight turns and very slippery surfaces

The CDL to me, only helps in runs with OVERLY uneven traction surfaces, with two tires on the same axle constantly lifting, spinning or unloading heavily, causing a lot of power to be sent to one end of the rig...

I WILL tell you this however...my 100 NEVER ceases to amaze me ! :grinpimp:
 
Hey, I know I'm opening up an old thread here, but I think this comment applies...

My girls and I went out today for the first time on a serious trail. I use the truck regularly offroad to get to hunting/biking/hiking spots but haven't seriously "'wheeled."

Lesson learned: Lock the CDL when climbing the steep loose stuff! The trail was rated moderate and most of the crowd was driving Wranglers and Rubicons and giving me :censor: about my LX. I had no problems the first couple of hours keeping up by driving in 4L, low gear, AHC high and "off", and choosing good lines. I was pleased with my clearance and traction with A-TRAC. Now and again a particularly steep and loose stretch would cause some limited wheelspin, but A-TRAC would catch it, and overall, we were good to go.

Then we got on a very long and steep stretch with good-sized loose rock and gravel and the farther up I got, the more wheelspin and rocks flyin' and rubber smoke everywhere and a truck full of women screaming bloody hell we're all gonna die why did you drag us along oh my god its all over our truck is dead we're gonna roll over...well, you can imagine!

So, I eased back down, selected CDL and climbed that sucker like I was back at the mall. These trucks are amazing!

The pic below is of the steepest section of the trail, but it was very clean and free of rocks and gravel, not like the one I described above. I spent the rest of the day with CDL selected except when turning sharp, and had no problems at all.

I was interested to read in my "2000 LX-470 New Features" manual that the VSC works to control yaw. The A-TRAC works to control traction. This fact may apply to some of the discussion above, in which questions were asked regarding CDL on or off when driving in snow. Since VSC is off when CDL is on, I'd guess that going uphill you'd want CDL on and when descending on slippery rock/gravel or especially snow, you'd want CDL off. You've still got ABS in both cases, but at least with CDL off the VSC can help you when descending in case of yaw.

By the way, I did this with Revos with over 40K miles on them. These tires have worn so well I am definitely getting another set, probably 285s next time around.

Cheers! :cheers:
IMGP3359 (Medium).webp
 
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