Engage CDL and keep ABS functioning?

Discussion in '80-Series Tech' started by MDarius, Feb 19, 2009.

  1. MDarius

    MDarius I break stuff. SILVER Star

    Likes Received:
    Apr 10, 2006
    Bountiful, UT
    I've searched and can't find. Seems there was an old thread that talked about the pro's and con's of having the CDL engaged and having the ABS working.

    I used to hate ABS when they first came out. ''I don't want some stupid faulty computer operating my brakes! I can do a better job myself!'' Now I feel differently. I've been sliding around in the snow this winter. My wife drives the 80 more than I do, with the kids in it, and I want to give her every opportunity possible to avoid a collision. Sometimes there is a benefit to driving the 80 in the city with the CDL engaged in the snow. It would be cool to have ABS functioning for missing the bumper of the car in front of you, as well as not sliding through that stop sign on the way to dropping the kids off at school.

    So, if you can't direct me to the existing thread(s), please chime in and educate me. Thanks.
  2. Bearcat80


    Likes Received:
    Mar 23, 2005
    Beaverton, OR
    It's not possible, because the locked center diff will not allow the brakes to operate independently of each other. The ABS works on each of the fronts and the rears together as three separate circuits. Link them together with a locked center diff ad I imagine the ABS computer would just quit, shut the door and go home to drink beer.
  3. 96r50


    Likes Received:
    Feb 25, 2007
    Just as an FYI, ABS is not going to stop you from sliding through a stop sign or sliding off the road. It tends to increase your stopping distance, since the brakes are pulsing on and off instead of staying on constantly. What it does do is allow you to steer AND brake at the same time (better than locked up tires would) so you can try to maneuver around objects while braking.



    Likes Received:
    Jun 1, 2005
    No can do. As suggested, the center diff locked means that the front and rear axles are locked and must rotate at the same speed always. ABS is for the open diff or the VC (deactivated). You do get ideal brake force distribution up to lockup with the center diff locked, but that may or may not be better than ABS depending on the situation.

    I run locked center in my 80 and in my quattros in the winter almost all the time, but I also run Blizzack ice tires.

    At the Steamboat Ice Track Event I ran this year, we found the locked centers were consistently better in control, accleration and stopping (given: all non-studded ice tires Blizzacks or Hoka Rsi's) than the latest and greatest ABS generations. This was 12inches of ice and light snow covered closed conditions.

    The VC in the 80 should give you almost full on torque locking, but the feel of control during turns and acceleration is just not the same. My other DD is a Audi v8 Quattro, which will fully lock the center diff on acceleration, and unlock it during any brake application. AFAIK, this is the only full time AWD system that works this way.

    Hope this helps

    Scott J
    94 FZJ80 Supercharged
    ACNA Gruppe-q Steamboat Ice Driving Experience 2009
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