F-250 4x4

How do you know that the 4x4 isn't working once you stop? Have you checked the vacuum hoses to the font diff? Has there been any front end work done recently?

When I start going the 4 wheel is not engaged and the rear tires spin. I checked all the vac lines and they are all attached. the only work done on the truck ever has been the high pressure oil pump that was replaced by Ford last month. My Buddy down the street has the same exact truck with the same exact problem. Could it possibly be moisture in the vac system causing ice? This has never happened to either truck and I could only guess it is from the arctic weather we are having here in the south.

So there is no cracks in any of the rubber or plastic vacuum lines? Have you had the front seals checked to see if they are leaking vacuum?

No, But I feel that, that is the problem. It has to be bad seals.

It very well could be sense if works all the other times. I will look to find out if you can check them and get back to ok. Thanks