Question about 2001 Ford F350 Super Duty SuperCab
The shift on yhe fly 4wd stoped working in my 01' f350. It worked the week before just fine, then I had to leave it sit out side of the garage for about a week, temps diped down below zero and when I went to use the truck after a week of no activity the 4wd would not work. Nothing; no clicks, no grinding, no light on the display, nothing! Tried locking the hubs in manualy, that didn't work either. checked all the fuses pertaining to 4wd, all seamed to be good, replaced realays, still nothing. check power down at the Tcase motor and never got any power to the plug. so I 'm pretty sure it's an electrical problem. hate to take it to the garage they want $90 just to tell what code comes up. was hopeing someone here could help with something simple I might have missed.
Most of the time it’s a Fuse, PVH,(Pulse Vacuum Hublock) ,Vacuum line or Vacuum pump.
ESOF 4WD Trouble shooting It is easier to trouble shoot the system if you have a “Mityvac” vacuum pump. Turn the ignition switch to run (you don’t have to start the truck) and the air controls to vent and the fan control to low. If the truck’s vacuum pump comes on wait until it stops running before each test (open the hood and you’ll hear it better). First you need to remove both lines (left and right vacuum lines) from the hubs. Plug the passenger’s side line and attach the vacuum pump to the driver’s side line. Switch the dash controller to 4WD high. The vacuum gauge should go to 10 in.-Hg. or higher. (It should hold the vacuum at 10 in.-Hg. or higher for 45 seconds on engage and 15 seconds on disengage.) Repeat the test plugging the drivers side and testing the passengers side. If you have the right amount of steady vacuum the problem is probably in the hubs. If you do not have the right amount of vacuum or it is bleeding off, plug the lines back on the hubs and go to the next step. Second remove the vacuum lines from the PVH (Pulse Vacuum Hublock). This is the solenoid located on the passenger side fender well behind the battery and in front of the vacuum pump. Plug the vacuum tester into the lower hose and wait for the vacuum pump to build back up and shut off. The vacuum gauge should read and hold steady at 10 in.-Hg. or more. If it does, the vacuum reservoir should be fine and not leaking, so go on to the next step. Third, plug the bottom line back to the bottom of the solenoid and hook the vacuum gauge to the top barb of the solenoid (not the vacuum line but to the solenoid itself). Try switching between 2WD and 4WD again. The gauge should read 10 in.-Hg. for 45 seconds on engage and for 15 seconds on disengage. If it doesn’t it is probably the solenoid (PVH) on the fender that needs replacing. This was my problem so this was as far as I have gone. If all these things check out, THEN you need to go to the hubs and check them for leaks with the vacuum tester. Most of the time it’s a fuse, PVH, vacuum line or vacuum pump and not the hubs. Does your ac/heater work properly when you switch modes (IE linger before going in?) or sometimes stay on defrost? These trucks have a vacuum pump that controls it and the auto hubs.If the vacuum pump or hose,fails those are easy to see symptoms.
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Posted on Jan 29, 2009
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