80 in ice & snow + question re CDL

[SUMOTOY]

Back to post 1.... With CDL on, in a straight line, torque allocation to the front and rear axles will follow weight distribution. In a turn, torque allocation will follow weight distribution and turning radius induced slip.

The question is, what gives better control? In a straight line, the locked CDL will always have Ideal Traction up to wheel spin (torque follows axle load). An open diff will have 50/50 torque allocation up to wheel spin (ideal only if weight distribution is 50/50)

The open diff will spin wheels in a straight line before the CDL-on will. in turns, it depends. The biggest factor to the question on CDL use is tires. IMO, a dedicated snow/ice tire can allow better control over a LTX equipped 80 with CDL on.

Try it both ways. As this thread indicates, there are a variety of opinions on what works. What works for *you* is the best strategy and answer.

HTH

ST

 

[lovetoski]

Okay... this has gotten my curiosity up. Not sure how many of you guys own cruisers other than an 80, but it seems to me that the CDL on position is just like a 40 or a 60 series in 4x4, right? I have each of those and can tell no steering or cornering difference when in 4x4 as opposed to 2wd (no locker in front). The tire slippage in turns should be in the front and rear diffs, thus without either of those diffs locked it's still open and tires left and right of each other can turn at different speeds. So IMHO the CDL makes no difference in turning much like a classic cruiser in 4wd sans lockers.

Am I totally off base??

The reason I posted in the first place is because I have a 60 and an 80, and I was intruiged by the differences I notice between the two while driving on ice/snow. As you say, a 40/60 in 4W (H or L) is like an 80 with CDL-on. The discussion that followed is interesting.

On my 60 though, when in 4W (both axles with open diffs) I find it much harder to turn. I think in this thread 80 owners with CDL mentioned this also when running CDL-on, but am not positive.

 

[SUMOTOY]

The reason I posted in the first place is because I have a 60 and an 80, and I was intruiged by the differences I notice between the two while driving on ice/snow. As you say, a 40/60 in 4W (H or L) is like an 80 with CDL-on. The discussion that followed is interesting.

On my 60 though, when in 4W (both axles with open diffs) I find it much harder to turn. I think in this thread 80 owners with CDL mentioned this also when running CDL-on, but am not positive.

In CDL on mode, both axles must turn at the same speed, so the front axle will resist a steering input that tries to shift torque allocation (rearward in turns). In an open diff, the 50/50 torque allocation stays the same AND will be 50/50 while allowing axles to turn at different speeds.

The effect or "feel" of this has a few variables attached to it. Wheelbase, track, tires, ackermann steering, alignment, and the amount power steering assist. I have installed a Gen 1 (locking center diff) into a late style audi with Variable Assist Steering. The effort required to turn the wheel up to full grind'em lock was single finger light.

I put a full flush synthetic oil change into my steering resevoir, and find that the return to center between locked and unlocked CDL (stock tires, etc) is not noticeable unless a close to fully locked steering wheel is present.

I highly suggest you do the CDL switch mod, and try this out for yourself. To answer your question, at high speeds I find the truck to be much more stable with the CDL on. YOMV, but choosing to have the *ability* to gather your own opinion for less than an hours worth of work, sounds like a good mod IMO.

ST

 

[landtank]

On my 60 though, when in 4W (both axles with open diffs) I find it much harder to turn. I think in this thread 80 owners with CDL mentioned this also when running CDL-on, but am not positive.

It's pretty much the same with an 80 with the CDL on. It's refered to as drive line windup. This happens due to the wheels traveling different distances (especially when turning) and the drive line wanting the two at the front to be the same as the two in the rear.

This typically goes un noticed on low traction surfaces such as sand, gravel and snow where it's use is more common.

 

[CoveredInRedMud]

Me too!


How funny is that. We both did the same thing... at the same chain. (that's all they're good for?)



We got snow overnight, too, and I just came back from our local K-Mart. I went back to playing in the snow pre-plow, with my 80 early this morning.

I won't start the argument again, but I did "play" with CDL and turns, short stops, starts from dead stops, etc.

And I wasn't the only one out there -- doing the exact same thing, I noticed.

Great minds think alike... !

 

[CoveredInRedMud]

It's pretty much the same with an 80 with the CDL on. It's refered to as drive line windup. This happens due to the wheels traveling different distances (especially when turning) and the drive line wanting the two at the front to be the same as the two in the rear.

This typically goes un noticed on low traction surfaces such as sand, gravel and snow where it's use is more common.

I agree. On dry cement, where tire squeaking is at its best, you'll already be squeaking more with CDL on in turns, and over the top with front and rear lockers on as well.

 

[PDoyle]

So, driving on the highway during/after snow fall with the CDL on at say 40-50mph is fine. When you have to do a lot of turning CDL should be off.
City driving in the snow CDL can be on. I would assume in town your not traveling at such a high rate of speed to loose control on a turn with the CDL on. Plus it's fun to drive in town after snow fall with CDL on...Every day driving stuff...

 

[landtank]

So, driving on the highway during/after snow fall with the CDL on at say 40-50mph is fine.

I do this quite often. On those long drives on I90 where I'm the only one on the road for miles. There are no sudden avoidance moves just gun and go.

 

[PDoyle]

Just want to re re reclarify....

 

[firetruck41]

So, driving on the highway during/after snow fall with the CDL on at say 40-50mph is fine. When you have to do a lot of turning CDL should be off.
City driving in the snow CDL can be on. I would assume in town your not traveling at such a high rate of speed to loose control on a turn with the CDL on. Plus it's fun to drive in town after snow fall with CDL on...Every day driving stuff...

If your comfortable with that, it is fine. Since CDL and ABS are "linked" with the 80, I prefer to keep my ABS intact when on the road, which means, I generally do not lock the CDL, when on the road.

 

[CoveredInRedMud]

If your comfortable with that, it is fine. Since CDL and ABS are "linked" with the 80, I prefer to keep my ABS intact when on the road, which means, I generally do not lock the CDL, when on the road.

Has anyone installed the CDL switch on their 80? Any online instructions available? It sounds like the question of having to choose between CDL and ABS (one or the other) would be solved if you had the indepenant CDL switch...

Of course that now begs the question of why the brillant minds at Toyota decided that ABS should be automatically disengaged with CDL on...

 

[firetruck41]

Has anyone installed the CDL switch on their 80? Any online instructions available? It sounds like the question of having to choose between CDL and ABS (one or the other) would be solved if you had the indepenant CDL switch...

Of course that now begs the question of why the brillant minds at Toyota decided that ABS should be automatically disengaged with CDL on...

Many have done it (look at my sig). Regardless of the switch, whenever CDL is engaged, ABS is disabled. If you could get ABS to be enabled, with some other modification, it would not work very well, if at all.
There should be a writeup in the FAQ, as well as on Slee's website.

 

[Romer]

you will find plenty of threads on the install using the search feature. Select advanced options. Select 80 forum and eneter your key words

 

[IdahoDoug]

Tym,

Actually, you're incorrect that there's no difference in cornering behavior due to the open f/r diffs. In a curve, all 4 tires follow a different path. The tighter the turn, the higher the % difference each tire must roll. Go drive through a puddle at full lock and you'll see 4 tracks. Also, you'll see the rear wheels have smaller diameter turns than the fronts. That means the rears go a shorter distance in the turn.

The rotational rates of the f/r driveshafts must therefore differ in a turn since the center diff "sees" the average of the two tires on a given axle - and as noted the rears turn fewer revolutions.

If the center is locked, such as a 40 in 4wd or an 80 with CDL on, something must slip in a curve. That's kinda what this entire thread is/was about. Some of us get the physics that forced slippage and compromised turning/handling MUST occur as a fact. Not a theory - a fact. Others feel that slippage is either non existent or that it actually helps handing on slippery stuff.

DougM