School me on the "automatic locking differential"

Discussion in 'General Chevy & GM Tech Questions' started by bigben55, Oct 13, 2008.

  1. bigben55

    bigben55 New Member

    I know how locking diff's work. My Nissan Frontier had an electronic selectable locking rear diff. My old Jeep Cherokee had an old school mechanical locker in the rear. I know how and when to use them. But, I'm not sure how the automatic locking rear differential works on my new 2008 Silverado 2500HD Z71. When it activates, does it always truly lock both rear axles or does it have a limited slip action as well? Does it work in 2wd or just 4wd? At what speeds and transfer case modes? School me.

  2. dwill3015

    dwill3015 Epic Member 5+ Years ROTM Winner 1000 Posts

    Hey Ben, we have a thread on here with some great info on the G80. Check out this THREAD
  3. MrShorty

    MrShorty Epic Member 5+ Years 1000 Posts

    G80 is a nice little unit, especially in the stronger 14 bolt axles. dwill3015's link has some nice videos showing the G80 in action, and a little of how it works.

    It is a true locker in that it positively locks both axles together. It's purely mechanical, there are no electronics or anything involved. The difference between a G80 and a traditional automatic locker (like a Detroit locker) is that a traditional locker is normally locked until it detects a need to differentiate. It can then unlock the axles so the wheels don't bark while cornering, then lock back together. The g80, on the other hand, is normally open until it senses wheel slip, at which point it can lock up. the conditions for lockup are: vehicle speed below ~25 mph and a rotational difference between the axles of about 100 RPM.

    It will operate anytime those conditions are met, regardless of transfer case position. However, because of the 25mph restriction, I found it most useful in low range. In high, it's too easy to exceed the 25 mph maximum. Also because of the 25 mph maximum, it works best for people who are easy on the throttle. Whenever I had one wheel on snow/ice/airborn and romped on the accelerator, that wheel with no resistance could exceed max speed faster than it could lock up. So it works best if you ease into, at least until it's locked. Like any locker, it doesn't readily unlock until the torque is off.
  4. dwill3015

    dwill3015 Epic Member 5+ Years ROTM Winner 1000 Posts

    Very nice touch! Thanks.

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