I can't find an answer to this in the forums. If I engage the system on the fly so to speak, it won't disengage until I stop. It goes into 4wd immediately when the switch is switched to 4hi. The dash light illuminates within 2 seconds. However, when I switch the switch back off the dash light goes off within 2 seconds, but you can clearly hear it's not released and it hunches going around corners.

When stopped with the front wheels off the ground you can clearly hear the xfer case motor engaging and disengaging and both hubs operate instantaneously. While moving around my property at 2 or 3 miles an hour the system also kicks in and out normally, just not between 15 and 45 miles and hour.

Both hubs are within 2 years old and the vacuum solenoid has been changed. Anyone got an idea what to check?

 

More than likely you have a vacuum leak in the system, as vacuum disengages the IWE's. At idle the engine produces more vacuum than at speed. Start testing the lines, reservoir tank, and check valves.

 

That doesn't explain why the transfer case motor is engaging and disengaging when stopped.

 

Does anyone know the sequence of events the system calls for to engage/disengage the 4wd? I know the vacuum system is unmonitored inasmuch as it doesn't know the condition of the hubs. So is the switch that turns the light on and off in the xfer case or the motor?

 

Actually it does, no? He has no problems at low/no speed with it disengaging. Unless he rigs up a camera, he can't be sure if it's doing the same at speed. The transfer case may very well be disengaged in both scenarios, just that the 4WD components are still being parasitically driven by the wheels.