I did a specific study on this technology (VC) when I was in college in 1986. This was brand new technology in testing at that time and was being touted as being designed to replace the transfer case and be able to make all cars AWD with minimal expense and weight additions.
I did tons of research (there wasn't any Interwebs then......) so I was calling tech shops, specialty 4x4 shops, and anyone I knew that knew someone that had a connection to automotive manufacturers to try to find out how they worked and what the intent was. I was very into 4x4 at that time, having built my own 4x4 in high school.
No, viscous couplers have no direct relationship to ABS. What the VC WILL allow is better control of ABS, now that we have computers and a sensor on each wheel and pressure sensors to control all of it.
ABS was in its early conception in the mid 1980's, as only the high-end cars were coming out with it, but absolutely no 4x4's, and even 2WD pickups only got it on the rear axle to prevent the rear from sliding out during heavy braking.
As far as being worried about "breaking things" when the front and rear are "locked together", that's the way ALL transfer cases were designed prior to about 1990. The early ones were gear-driven (specifically the Rockwell T-221) and the later ones were chain driven and you had hi range 4x4, Hi range 2WD, Neutral, and Low range 4x4. The front and rear DS turned the same speed in all cases and were locked together. When we would turn corners with the hubs locked in, the truck would "hop" or the front tires would squeal as you made the corners. Realize that at that time, the closest thing to an SUV was a Chevy Suburban, a K-5 Blazer, a Ford Bronco, or a Dodge Ramcharger. These were designed as a truck first, with some luxury, but it was still understood that the people driving them had a specific need for one of these and understood what NOT to do. (tight corners on pavement while locked in 4x4)
Once the tax laws helped folks figure out that they could buy extended cab pickups or Blazer, Ramchargers, or Broncos and still deduct them as a TRUCK, folks started buying MORE of them. When sales went up, so did the problems, because Sally housewife was driving a TRUCK in 4x4 and didn't have a clue that she wasn't SUPPOSED to be able to do that. The demographics of a 4x4 owner started to change.
So, eventually, the VC was invented to help cushion the driveline (clunk damper) and to make it so those folks that didn't have a clue could drive what was still perceived as a truck and not complain and not break it.
Now, here we are, 29 years later, and we've figured out that for the HD work that we want our truck to do doesn't do well with a VC. But I'll guarantee that if you let your
drive the truck without a VC, there will be either bitchage or breakage at some point, because most don't care, they just want to drive the truck and not have to worry about it.
What's my point? I was pissed because I got a C- on the paper because my instructor didn't think I put enough research into it and he didn't see the relevance to the drive line design we were working on with agricultural equipment. pppfffttthhttt!!! What did HE know?!?!?!?
If you look at the 4x4 technology that has developed over the years from when Willys first started using it during the war, lots of things have changed, but a few have remained the same. There were a few good ideas over the years, but there were more bad ideas (self-locking front hubs on GM for "full-time 4WD") Now that we can throw thousands of HP at a 4x4 and make it do all sorts of stupid things, we help develop new, innovative ways of thinking and we can make it all better. Who knows, maybe in the next 29 years, we'll have FLYING cars!
Thanks for reading!
