what is this button for?

[mross45640]

i just purchased a 1999 jimmy yesterday,on the push button 4x4 it has a button that says auto 4x4 when i push this button the dash says,service 4 wheel drive but it works fine if i hit buttons marked 4hi or 4lo,what is that auto button for?guy i bought it from said it has been like that since he bought it and has no idea what it is for.any help would be appreciated thanks mike

 

[Mic_]

automatically puts in on and out or 4x4





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[Morbugs]

i have a '99 jimmy SLT/Envoy and I have that switch also, forgive me "Mic" but that doesnt really explain the question, but does the trans know when a wheel is spinning and engage 4x4 (front wheel) , So when thinking could i conceivably ~ leave it in auto 4x4 during 'winter' driving -Common sense tells me to leave it in 2x4 for regular driving

 

[mogleybear]

The 4x4 auto allows the vehicle to go in and out of 4 wheel drive when the sensors detect a wheel spin / loss of traction. It will operate with power to the rear wheels and when the sensors detect a loss of traction it will engage the front wheels. On some vehicles you will be able to feel it kick in and some you can't. Leaving it in 4x4 auto is not supposed to cause any problems with the drive line on dry pavement. My guess would be with the service 4wd light coming on would indicate an issue with the automatic sensing system. I'm not sure if it goes through the anti-lock brake sensors or not. Engaging it in 4 hi or 4 lo vs auto overrides the auto function and engages 4 wheel drive at all times.

 

[Morbugs]

thanks - it is just confusing ... good explanation though