Hello ;
I have a 1999 F150 4x4/ the 4 wheel drive is not locking all of the sudden, lights indicate it is in ,and the trans feels as if it is in but the front wheels are not locking . Is there a fuse or relay that may be the problem, and if so where would it be located, i have lost my owners manual.
Thank You,
Adam
vanmedic@yahoo.com

 

The front axles on these trucks lock in by way of vacuum. Start at the front axle and find the vacuum lines. (Make sure it is the vacuum line and not the vent tube.) Follow the vacuum lines up the the engine compartment and look for and broken or split hoses. I'd start with that. Since the 4x4 light lights up that means that the elec. part of the system is working. Hope that helps, let us know what you find.

 

Thank you!! you hit the nail on the head, it was a vaccume problem that is now fixed.
Thanks,
adam

 

Very glad I could help!!!!!!!!