I have a 98 F150 with the shift on the fly floor lever. When I put it in 4WD, it sometimes clicks on and sometimes doesn't. I drove in the rain about 2 hours on the expressway and the light turned off by itself. Also, it seemed as if at about 60 mph, the transfer case sounded like it rattled...Any help?

 

i didnt know that you could have a floor lever on a 98, mines a **** on the dash.

and im not sure exactly what your problem is, is is not going it to 4wd, not staying in 4wd, not going in to 4wd, or going in by its self when you dont want it to?

 

After driving it for a while, if I try to engage the 4wd, the lever will move but it will not engage and the light wont even go on...

 

I had the same problem on a 97 f150 check the vacumn lines on the fire wall. Mine were cracked and even though the lever is on the floor, most assume it is mechanically engaged when in fact it is a valve that uses vacumn to engage the transfer case. Weird design and it took me a year to find the problem. Worked after I redid the hoses. It is located on the firewall I don't quit remember which side.