The difference between 4 wheel high Auto and 4 wheel high Part Time

[Joe98]

The old JK has 4 a position transfer case.

2 wheel High
4 wheel high
Neutral
4 wheel low


The JL has a 5 position transfer case

2 wheel High
4 wheel high Auto
4 wheel high Part Time
Neutral
4 wheel low


So, what is the difference between, 4 wheel high Auto and 4 wheel high Part Time?



From the manual:

4 wheel high auto

This range sends power to the front wheels. The front axle is engaged, but the vehicle's power is sent to the rear wheels. The four-wheel drive system will be automatically engaged when the vehicle senses a loss of traction.


4 wheel high part time

This range maximizes torque to the front driveshaft, forcing the front and rear wheels to rotate at the same speed.
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[trainsafe]

The name might be a bit misleading. As I understand it the 4wd part time mode is your traditional 4 hi. The transfer case finds the front wheels and rear wheels together. They spin at the same rate. It is named part-time because you only want to use it on loose or slippery surfaces. Long term use on dry roads will cause additional wear to the drivetrain.

The auto mode will use the ABS sensors to detect when traction is compromised and engage the transfer case for a bit.