Auto 4wd

[jman_07]

So i have a 2002 Chevy Suburban with the Auto-Trac transfer case. Just wondering how the Auto feature works because when engaged the fronts do pull but i can still spin the rear tires pretty good. For Example when the front is on cement and the rear on sand In Auto mode the front pulls but the rear is still allowed to spin.

I was told In auto Mode it works Pretty much like An all wheel drive. It can send very little or alot of power to the front tires depending on how bad the traction situation is. And i was told this is possible because of the operation of the clutches is this true???


Thanks


Jared.

[MT-2500]

In auto mode it should transfer power to front or rear as needed.
But you say the front stills pulls.
If it pulls enough in front to keep you from getting stuck it may be OK.
They also need proper service with the proper fluid like the GM transfer case fluid.
Has you ever been serviced?
How many miles on it?
Any check engine or transmission or transfer case lights on?
You can also check for problems with a transfer case/transmission capable scanner.
Post back any codes.
MT

[j cAT]

Originally Posted by jman_07

So i have a 2002 Chevy Suburban with the Auto-Trac transfer case. Just wondering how the Auto feature works because when engaged the fronts do pull but i can still spin the rear tires pretty good. For Example when the front is on cement and the rear on sand In Auto mode the front pulls but the rear is still allowed to spin.

I was told In auto Mode it works Pretty much like An all wheel drive. It can send very little or alot of power to the front tires depending on how bad the traction situation is. And i was told this is possible because of the operation of the clutches is this true???


Thanks


Jared.

In auto 4x4 with locking differential my vehicle will spin all tires at the same speed .....i did this a few times in my driveway when it was totally iced up.....when fronts are on solid ground rears on ice or sand the rears should not spin faster than fronts.... so if your vehicle is doing this the front axles must be slipping.....you will have dtc failure codes if there is a problem...get dealer or a repair shop that can read these drivetrain codes and report back with results....


in auto 4x4 your vehicle will first must sense a slip before 4x4 is engaged!!!!!!this is a very few revolutions ...


in auto 4x4 the fronts are locked together , but not engaged to transfer case...when slip sensed then the fronts engage to rear all are then locked and rotating at same rpm...

[chuck's]

From reading a service manual,there is a clutch pack in which the encoder motor is connected to via internal linkage.With the slippage of rear wheel,the 4x4 module senses the slippage and then will send electrical power to the encoder motor.Via the internal linkage,the clutch pack gets proportionally engagaged to power the front drive shaft.It doesn't lock the clutch pack fully as if in full time 4x4.One drive shaft will turn faster than the other if alot of engine power is applied.I hope this helps to give you a better understanding how it works.

chuck's

[j cAT]

Originally Posted by chuck's

From reading a service manual,there is a clutch pack in which the encoder motor is connected to via internal linkage.With the slippage of rear wheel,the 4x4 module senses the slippage and then will send electrical power to the encoder motor.Via the internal linkage,the clutch pack gets proportionally engagaged to power the front drive shaft.It doesn't lock the clutch pack fully as if in full time 4x4.One drive shaft will turn faster than the other if alot of engine power is applied.I hope this helps to give you a better understanding how it works.

chuck's

In auto 4x4 the pcm controls the 4x4... there are 3 sensors... 2 front one rear...

when the pcm sees different speed sensor input the transfer case encoder engages....this should happen very quickly if not you may have what this vehicle owner has happening.... there is not much slippage if any....when my vehicle locks in 4x4 and this does happen on dry ground as i may rotate tires when i put vehicle back down and turn the steering wheel to pull out of my driveway the wheels are jumping because they are all locked ...........the vehicle will shake and leave skid marks on pavement...

this is not proportionally engaged....also it takes more non slippage sensed to release 4x4 than engagement of 4x4........

if it takes too long for engagement or there is slippage transfer case is in need of repair.......



it does not apply more or less 4x4 depending on how much the wheels slipping.....