Ok I have a 1997 f150. 4.6l. I have no four wheel drive. it just quit working. Some of thr things I have done.

1) Replaced transfer case motor. Do not think the last one was bad.

2) Replaced 4X4 switch in the dash board. Do not think this was bad.

I am buying a 3way vacum check vavle. It is for the heat control. but the other side is for the 4X4 somehow.

Let me know if you can help at a loss here.

 

sounds like a vacum leak or a blown fuse i have the same model and year of truck only its the old style manuel shift 4x4 lever but my fuses randomly blow from bein so old so i replaced em all and havent had a problem since

 

may be vacum buy i have checked all the fuses.

 

need to check to see if you have a vaccumme source going to your front end..... and make sure it has vaccume while running in 4wd

 

X2

 

i have vaccume at front end. how can i check the CEM or whatever u call it.

 

I should make a stickie of this.

Lift and support the front so the wheels are off the ground. Key ON engage 4Hi. Try to turn the front Driveshaft. If it doesn't turn the Transfer case is OK. With it still in 4Hi and the driveshaft locked rotate one of the wheels. The other should rotate in the opposite direction. If it doesn't the front axle in not engaged.