After doing a test drive after installing an 8" lift on my 2000 6-speed manual diesel F-250, I noticed that while the 4X4 engages, it won't shift into Low. I've had this truck 7 years and know the drill: complete stop, foot on the brake, clutch to the floor, transmission in neutral, and it usually takes a couple seconds. I've tried different combinations of backing up first, going straight from 2WD to 4Low, etc and still no 4Low.

As far as I know the ESOF transfer case is all electronic and vacuum doesn't play a role. I don't recall ever seeing a vacuum line coming out of it anyway.

Anybody got any ideas on this one?

 

If it switches in and out of 4WD, then the shift motor, relays and GEM module should all be OK. Sometimes I have to let mine roll a little, with just enough brake to activate the brake switch.

You also might have a problem with the brake or the clutch switch. Does the cruise control disengage with just a very light touch to the brakes? Does it disengage when you press the clutch. These would be ways to test the operation of those switches.

 

No problem with the cruise control turning off with application of the brakes. If there were I wouldn't be able to shift into 4X4 at all. Not sure about the clutch though. I don't recall ever having to put the clutch in to shift into 4High, just 4Low. I'll take a closer look at that since I had clutch work done recently.

 

You don't need to press the brakes or the clutch to shift into or out of 4x4 with ESOF. You can shift at up to 50MPH.

The GEM computer needs to see the BPP switch on the brake pedal and the clutch switch activated in order to switch into and out of Low range.

The reason I asked about a very light touch deactivating the cruise control is because there are two switches. The BPP switch on the brake pedal is the primary signal to the PCM to disengage the cruise, and also to the GEM to allow a switch to Low range. The brake pressure switch on the brake master cylinder is a back up switch that will disengage the cruise, with much more brake pedal pressure, in the event that the BPP switch fails.

 

I'll check it out. I've had both the clutch and GEM module changed in the past couple of months so both are suspect. I might look at over-riding one or both safeties since this system seems to be overly complicated.

 

cruise control should disengage with very light pressure to the clutch as well...

 

Well, no joy on the switches. Both the clutch and brake pedals each disengage the cruise control with a light tap. Anybody know if there's a second switch on the clutch indicating that it's fully depressed? I seem to recall that the clutch pedal had to be all the way on the floor before Low would engage.

The manual says the clutch has to be fully depressed OR the transmission has to be in neutral. It never engaged without the clutch on the floor previously, and whether it was in neutral or not made no difference. I don't think the standards have a transmission gear position sensor.

 

pb blast all your linkage.

 

This electrical diagram seems to indicate that the clutch switch has 3 poles. But it also seems to indicate that the center pole isn't used on diesels at all. I also could not find any more information, such as whether one or more poles are switched when you first start pressing the clutch vs one or more poles being switched when the clutch is all the way to the floor.

This is all the information I could find.

 

yes, that's the one that allows you to start your engine... if that one didn't work, you'd know it.

 

But according to everything I can find, there is just the one switch. So it must serve both purposes.

I'm going to make an educated guess and say that the Clutch Pedal Position switch activates one pole when you start to press the clutch, and the other when the clutch reaches the floor. It would seem to make sense that way.

Assuming the first part of the switch deactivates the cruise, and the last part allows the starter to work, and it would make sense that the last part would also allow the 4WL shift (you'd want the clutch all the way down, I'd think), then I would also think that that switch could still be the problem.

I would replace it. But, like I said, that's really kind of a guess.

 

I think the "Neutral or clutch" requirement is just so the gears can turn. There might not be any electrical check on it. If the gears can't turn, they cannot engage.

 

Thanks for the research and posting the diagram dchamberlain. I think you're both right about the clutch switch. If I can start the engine then the switch is working as it's supposed to. I'll consider the clutch switch to not be the problem.

My next concern is that this problem may be connected the to the GEM module I had replaced a month or so ago. If it is, it's probably beyond my ability to diagnose.

I'm taking it in to the transmission guru that put my new clutch in a few months ago to see if he knows.

 

Curious if you ever solved this problem? I have the exact same issue as you and i'm sure there are many others who stumble upon this thread. Thanks

 

also curious my 2007 F250 6.0 cruise control no longer works and my 4 low doesn’t engage. I have done just about everything and can’t figure it out