Originally Posted by ruger#1
Haven't had truck very long and want to know if Axles have to be in auto or lock for low. The light on instrament panal doesnt come on when I switch to 4low, just when I go to 4high. Thanks for any help...
They can be in both.
The hubs can be in either position - auto or manual, in either of the following modes: 2HI*, 4HI, 4LO. The hubs are designed to work in the Auto mode in all conditions. Note that I intentionally used the word "designed", because they don't always work as intended. That's why Ford included the manual mode. Due to poor maintenance, vacuum leaks, and other issues, the Auto mode doesn't always engage the hubs (or engage both hubs, for that matter).
The 4x4 light on the dash is indicated by the transfer case, not the front axle. If the light illuminates in 4HI, but not 4LO, this means that your truck is not going into 4LO. I would start by checking fuses and then the wires on the back of the 4x4 switch and on the transfer case shift motor. Since 4HI engages, and 4LO doesn't, might be as simple as a bad 4x4 switch (on the dashboard).
* - Driving with the hubs locked in 2HI (assumes hard surfaces and 4x4 not needed) will reduce fuel mileage and increase wear and tear on front end components.