4 Wheel on The Fly Not Working - Diesel Forum

jcsanborn · 11-01-2009, 09:44 PM

We were just down in Arizona driving in deep sand and when I shifted into 4x4 on the dash nothing happened, even though the 4x4 dash light came on. And, I got stuck. When I got out and locked in the hubs the front wheels started driving so we know the transfer case is ok, just no hub lock. We had several days of this kind of driving and each time we locked the hubs we were ok. At the same time I was continuing to shift the dash lever to 4x4.

I don't know how the dash shift communicates with the front end, but would appreciate some ideas about what I am dealing with. I have shifted into low 4x4 and the truck does go into low gear ok, just no front end drive.

This is a 2003 6.0l 250 with about 100,000 miles.

John Sanborn
Delta, CO

KevinTamu · 11-02-2009, 01:09 PM

You might have ripped a vacuum line off, I'd look around for one that's loose.

**my03psd** · 11-02-2009, 01:28 PM

Definetly vacuum problem, either torn line, bad vac. pump, or like my truck it was leaking at the hub bearings relaced bearings and been fine ever since.

3/4tonman · 11-08-2009, 12:13 AM

If it is the vacuum seals they are pretty pricey from Ford too. Found out the hard way that mine wasn't locking same as you. When I replaced the seals, bearings, and left outer half shaft I also upgraded the lock out with Warn locks. I had to replace the lock outs anyway. The OEM hubs were seized up around the oring and wouldn't twist. Thank you previous owner who did no maintenance!