Joined
·
1,387 Posts
I've rebuilt a few older gm auto transfer cases and had a few with the auto 4x4. You can drive in 4auto all the time, but not in 4hi.
Here's how they work.
2wd: front axle disconnected
4auto: the front axle engages and the front axle is ready to take torque from the transfer case. When the truck detects the rear tires slipping it'll clutch in torque to the front axle. There is a clutch motor on the shift rail and a pack of ten clutch discs and nine friction discs (or vise versa). It can give up to 50/50 but if the truck moves and gets going the power will go back to the rear tires.
4hi: front and rear driveshafts both get equal power, non differentiated (binds on hard ground while turning)
4lo: front and rear both get equal power like 4hi but thru a low range planetary gear set
The negative to running 4auto all the time is that you are now spinning a front driveshaft which, agurably, adds wear and also an extra 40lb you are spinning all the time. Keep her in 2wd until you need 4.
Tim
Here's how they work.
2wd: front axle disconnected
4auto: the front axle engages and the front axle is ready to take torque from the transfer case. When the truck detects the rear tires slipping it'll clutch in torque to the front axle. There is a clutch motor on the shift rail and a pack of ten clutch discs and nine friction discs (or vise versa). It can give up to 50/50 but if the truck moves and gets going the power will go back to the rear tires.
4hi: front and rear driveshafts both get equal power, non differentiated (binds on hard ground while turning)
4lo: front and rear both get equal power like 4hi but thru a low range planetary gear set
The negative to running 4auto all the time is that you are now spinning a front driveshaft which, agurably, adds wear and also an extra 40lb you are spinning all the time. Keep her in 2wd until you need 4.
Tim