We have a 1997 Expedition XLT 4x4 (5.4L V8) with just under 150,000 miles on it. We bought it used about a year ago. Ever since we got it, there has been a very loud grinding noise from the front end, accompanied by a lot of vibration. It's not bad until the vehicle reaches about 60mph, and gets worse as the vehicle goes faster than that. The noise/vibration gets really, really bad at about 75-80mph. It seems to be worst when my foot is on the gas. It will sometimes go away completely for a few seconds at 75mph or so if I life my foot off the gas and cruise a while. I had a transmission shop look at it. They put the rear end on jack stands, got the wheels up to 60 mph, and noticed that there was a lot of vibration in the front transfer case and the part of the drive shaft that enters the front transfer case. Their verdict is that the transfer case is bad and needs to be repaired or replaced. They did not get the impression that the transmission was to blame.

Some more info: for some reason, I cannot switch into 4wd High ("4H") or "4L." If I switch into "A4WD," the dashboard "A4WD" indicator light comes on, but the A4WD light stays on if I switch to 4H or 4L (the "4x4" and "LOW RANGE" lights never come on.) I tried using 4L to pull another truck that was stuck in some mud. The A4WD light was on, and before we got the other truck unstuck, the front wheels did spin in the dirt, though I don't think they spun as fast as the rear wheels. I could be wrong, but I got the impression that the 4WD system was operating in "A4WD" mode, not "4L."

I looked at some other threads in this forum and noticed that some people who have had transfer case problems have had luck after disabling the 4WD system by pulling the 4WD fuse. I tried removing the #17 30 amp fuse from the Power network box under the hood (it's labeled "Four-Wheel Drive (4WD) transfer case motor ans clutch" ). This did not solve the problem. I also tried removing that fuse and the 10 amp #23 fuse from the interior fuse box on the driver's side (this one is labeled "Electronic flasher, 4WD vacuum solenoids, trailer tow battery charge relay, console climate door actuator, auxiliary blend and mode door actuators, auxiliary pot switching module") The
problem persisted with both fuses removed.

The Ford dealership has not looked at the vehicle yet, but told me over the phone that a replacement front transfer box will be $2,350 with labor, parts, tax, etc. included. Suffice to say, I'd like to spend less if at all possible!!

What are some other possible causes for this problem? Is there a chance that I might be able to get it fixed without having to replace the transfer case? If not, is there any easy way to convert the vehicle to 2WD only, at least until I can get enough dinero to fix the 4WD problem?

 

where is the fuse for the four wheel drive on my 97 expedition