The ABS is disabled with the the CDL because the front and real axles are ridgidly connected at that point. Not only is all the drive force connected, so is the braking force. ABS get's confused by this.
Viscous Coupler removal and AWD (2 Viewers)
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The ABS is disabled with the the CDL because the front and real axles are ridgidly connected at that point. Not only is all the drive force connected, so is the braking force. ABS get's confused by this.
I've never really understood this argument, as most other 4x4s will leave ABS on even in 4WD (GM pickups and Nissan SUVs are the ones I know of personally). I could see Toyota thinking that ABS is usually unwanted offroad and deciding that rather than having an ABS kill switch, they would tie it in with the CDL switch since that is usually engaged in most offroad situations.
I think Rich and Christo are right. Having had a seized VC, and removed it, the clunkiness of the driveline is very apparent now. I can also state I was surprised on my driveway last winter when the back end flipped around on me on snow and ice...lesson learned, I should have had cdl engaged.
My guess on the ABS, is in a non-locked 80 like mine, I can have wheel spin on one axle and none on the other axle when cdl is locked, probably confusing abs?
Last edited:
Grench
SILVER Star
Here's the short of it.
CDL locked means that the front and rear drive shaft are linked.
If the ABS engages on the rear axle and the center diff is locked, it WILL send vibrating shocks through the drive line to the front wheels too.
The rear ABS engages both DS and PS if -either- is slipping. Since this is pulsating the rear brakes together, it effectively can stutter-stop the rear drive shaft. If the CDL is engaged, it will also stutter stop the front drive shaft and potentially put that strain on the transmission and engine as well.
To correct the above poster...
If you have the CDL on, you can not spin only one tire. You will spin one on each axle. Think of it this way...
No lockers engaged (FR RR CDL all off) you can spin one wheel. Turning is easy as each wheel can follow a different radius track and turn at a different rate.
CDL engaged (FR RR off) you can spin no less than one wheel per axle = 2 wheels. Steering is mildly compromised and it is possible to make some tire scrub if you're turning on a high traction surface.
CDL engaged, RR engaged (FR off) you can spin no less than three wheels (2 rear locked + one front) and the front wheel that spins would rotate at twice the rate of the rears (truck not moving). Steering can be very problematic as the rear wheels are essentially a linked pair of tank treads at this point. The rears will only push forward and to turn the truck must overcome the traction on one of the rear wheels to turn.
CDL engaged, RR engaged, FR engaged means that all 4 wheels must turn and they must do so at the same rate. Sounds great, but it is nearly impossible to turn the vehicle in this state. If you lock it up this way and hit the gas, you'd best be pointed in the direction you plan to go. Also, if you're on a very low friction flat surface (icy interstate) the vehicle WILL AUTOROTATE you right into the nearest ditch.
CDL locked means that the front and rear drive shaft are linked.
If the ABS engages on the rear axle and the center diff is locked, it WILL send vibrating shocks through the drive line to the front wheels too.
The rear ABS engages both DS and PS if -either- is slipping. Since this is pulsating the rear brakes together, it effectively can stutter-stop the rear drive shaft. If the CDL is engaged, it will also stutter stop the front drive shaft and potentially put that strain on the transmission and engine as well.
To correct the above poster...
If you have the CDL on, you can not spin only one tire. You will spin one on each axle. Think of it this way...
No lockers engaged (FR RR CDL all off) you can spin one wheel. Turning is easy as each wheel can follow a different radius track and turn at a different rate.
CDL engaged (FR RR off) you can spin no less than one wheel per axle = 2 wheels. Steering is mildly compromised and it is possible to make some tire scrub if you're turning on a high traction surface.
CDL engaged, RR engaged (FR off) you can spin no less than three wheels (2 rear locked + one front) and the front wheel that spins would rotate at twice the rate of the rears (truck not moving). Steering can be very problematic as the rear wheels are essentially a linked pair of tank treads at this point. The rears will only push forward and to turn the truck must overcome the traction on one of the rear wheels to turn.
CDL engaged, RR engaged, FR engaged means that all 4 wheels must turn and they must do so at the same rate. Sounds great, but it is nearly impossible to turn the vehicle in this state. If you lock it up this way and hit the gas, you'd best be pointed in the direction you plan to go. Also, if you're on a very low friction flat surface (icy interstate) the vehicle WILL AUTOROTATE you right into the nearest ditch.
Grench
SILVER Star
Fixed it for ya
That was me being concise.
not sure about the other trucks but ours is a 3 zone setup. The rear axle in it's entirety is a zone even though there are sensors at each wheel.
True, I hadn't thought about that. I'll take a look at the other trucks I mentioned next time I get a chance.
GM trucks were all 3WAL. Not sure if they still are.
hallo to all writers of this topic. next week i will remove VC. It is totally locked,
every time the toy makes a curve on asphalt, the hairs on my back become vertical like iron wires
every time the toy makes a curve on asphalt, the hairs on my back become vertical like iron wires
Interesting, you sure it’s not your center diff lock stuck in locked position? If a VC fails you just have an open diff and that’s it, it is not possible for it to be fully locked as far as I know.
i'm pretty sure, because when I insert the center diff lock i can feel engaging on the trasmission system. I used for long time center diff lock disengaged on sand. I think he went in overtemp and silicone oil was damaged. Are you sure when vc fails it become as open diff and not as locked diff?
ppc
M Go Blue
The VC normally fails in a locked up condition.
yes, i'm pretty sure.
the defect emerged gradually and worsened over time. not just in one time like a defect of central differential lock. Next week I will try to open the VC
the defect emerged gradually and worsened over time. not just in one time like a defect of central differential lock. Next week I will try to open the VC
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The VC becoming tight or fully locked is somewhat common. Remove the front end of the rear driveshaft, tie it out of the way then take off the transfer rear housing. Pop off the snap ring and dump it and the VC into the metal recycle bin. Pretty easy job, takes a bit of RTV and gear oil.
I stand corrected, what he said!
good morning and tnx a lot for your comment. I'm sure i will do this job. tnx again
SmokingRocks
hopelessly addicted to Cruisers
I miss my vc for winter driving. Its strength is handling intermittent losses of traction at various wheels very well as it instantly and smoothly proportions powers away from the slips.
Without my vc, on ice the front end breaks loose first, usually in a turn which creates understeer. Sure I lock my CDL, but this then overdrives one axle depending on the condition which usually results in oversteer. The VC is a must for winter driving on ice, nothing transfers power away from the slips as quickly and smoothly as it does.
Additionally it’s nice to have when wheeling, you can spend most of your trail without having your CDL engaged. This makes turning on switchbacks easier and tighter and it minimizes wear on your tires and gears.
I miss my VC.
Without my vc, on ice the front end breaks loose first, usually in a turn which creates understeer. Sure I lock my CDL, but this then overdrives one axle depending on the condition which usually results in oversteer. The VC is a must for winter driving on ice, nothing transfers power away from the slips as quickly and smoothly as it does.
Additionally it’s nice to have when wheeling, you can spend most of your trail without having your CDL engaged. This makes turning on switchbacks easier and tighter and it minimizes wear on your tires and gears.
I miss my VC.
Box Rocket
SILVER Star
Interesting. With my '93 the truck had a non VC tcase and I never really experienced what you describe, other than getting oversteer with the VC locked.
SmokingRocks
hopelessly addicted to Cruisers
It's quite evident when you live in an area that has snow/ice packed mountain roads for weeks.
