Chevy Silverado ZR2 AWD Quirk & the LC200 (1 Viewer)

[Mineral]

The below article recently came up about the 2022 Silverado ZR2 “magically” shutting off 4wd mode while off-reading.

The Chevrolet Silverado ZR2 and the Mystery of '4WD Off'

The ZR2 is a mean trail machine, but I accidentally discovered its weak point.

www.caranddriver.com

Curious if the author’s observations are how all awd systems work (ie including the LC200) or are they overly generalized?

Fwiw, I’ve never had my LC200 decide to disengage the center diff on its own accord…

“So when you're in high-range four-wheel drive, or low range, the front and rear axles aren't really physically locked together. They have that clutch in there, doing its best, but with too much load it can tap out…

““In trucks with a part-time transfer case, the front and rear axles are physically locked”

 

[04UZJ100]

When the 200's diff is locked, it's locked, mechanically. It is full time AWD unless the center diff is locked. The 200 will never be in 2WD mode unless mechanical failure (rare) or front drive shaft disconnection.

GM makes junk. Anybody that thinks otherwise simply falls for their marketing.

 

[highfructose]

What is the nature of our center differential lock? Is it a helical/torsen? Or clutch based?

 

[rlynch356]

The Center diff is a planetary gear set with a chain drive... mechanical Full time 4wd...
Reading through the Article.. the ZR2 is really a part time system, would normally would be classified as an AWD system since it uses a clutch to tie the front and rear drives together.. it would basically disengage the front when not needed.
2 foot driving is pretty key off road, so basically it was designed by engineers who had no idea what is really needed off road. (IMHO)
The 200 is a purely mechanical system, which is always 4WD..

 

[highfructose]

The Center diff is a planetary gear set with a chain drive... mechanical Full time 4wd...
Reading through the Article.. the ZR2 is really a part time system, would normally would be classified as an AWD system since it uses a clutch to tie the front and rear drives together.. it would basically disengage the front when not needed.
2 foot driving is pretty key off road, so basically it was designed by engineers who had no idea what is really needed off road. (IMHO)
The 200 is a purely mechanical system, which is always 4WD..
View attachment 3122951

So it’s a worm gear something or other with planetary gears that locks the center diff? Sort of like a trutrac/helical limited slip?

 

[bloc]

So it’s a worm gear something or other with planetary gears that locks the center diff? Sort of like a trutrac/helical limited slip?

There is a planetary for the low range and a Torsen (I believe type C but not 100% sure on that detail) limited slip differential between the front and rear drivelines. When you engage the center diff lock a collar slides across splines locking the front and rear output shafts together.

In this particular vehicle you can be in low range with the center diff still unlocked, which has advantages for turning radius on tight trails. Then for any climbs or descents engage the CDL to even the torque to each wheel and avoid traction loss by the unloaded axle.

 

[rlynch356]

Yep its a Torsen Limited Slip differential(T-3), with full lockup when engaged for 50/50 torque split. it can be locked/unlocked in both High and Low ranges.

 

[highfructose]

Yep its a Torsen Limited Slip differential(T-3), with full lockup when engaged for 50/50 torque split. it can be locked/unlocked in both High and Low ranges.

Any idea how much slip it will allow before automatically engaging? Or is it not that kind of torsen?

 

[rlynch356]

From what I have seen (not verified in factory literature though so full disclaimer)... is a normal drive torque split of 41/59% and an adjustment range of 30/70% to 50/50%

It is always engaged since it is a full time 4WD system
i.e. the front wheels are always powered.

 

[highfructose]

From what I have seen (not verified in factory literature though so full disclaimer)... is a normal drive torque split of 41/59% and an adjustment range of 30/70% to 50/50%

It is always engaged since it is a full time 4WD system
i.e. the front wheels are always powered.

So up to 70% to the front of the rears are slipping…minimum 30% power even when unlocked…minimum 50% power when locked?

 

[rlynch356]

Other way around - from 30% Front to 50% front via the torsion center diff.
It does not get above 50%. Normal Operation is 41/59%

That is Unlocked.... Purely the Torsen Diff doing its thing..

Locked is always 50/50% and does not vary from that. The Torsen torque biasing diff is no longer active.