I've read thread after thread and sticky after sticky on this forum and others and can't find an answer to my problem. I have a 2001 F-150 4X4 Supercrew with 5.4, automatic transmission and ESOF. When I switch the selector **** to 4H everything works fine. When I try to switch to 4L, (with the transmission in neutral, foot firmly on the brake and stopped) is when the problem occurs. I can hear serious grinding for a few seconds from under the truck (I picture gears are grinding) and then a solid clunk but it is not in 4L. The LOW RANGE dash light does not illuminate and the 4X4 dash light goes out. I have to restart the truck, switch it back to 2H and then I can start the process all over with no issues UNTIL I try to put it in 4L. I would appreciate any guidance on what to check. Thanks for reading.

 

Ok. 60+ views with no response? I guess I'm asking what happens mechanically when selecting 4L so I know what to check? Any thoughts would be appreciated.

 

I'm probably not the best person to answer but maybe my response will start some chatter.

From what I understand when you switch to 4 wheel drive the switch relays the message to a 4 wheel drive vacuum solenoid which then actuates the hubs to engage the 4 wheel drive system. It might be a problem with one of those to parts?

But you probably already read about that. sorry

Is the grinding coming from the diff.?

 

That's what I'm unsure about. I need to be near the underside of the truck and have someone switch the selector **** and try to hear where it's coming from. I was hoping someone who was knowledgeable about the system could tell me where to start or what is SUPPOSED to happen when it shifts into 4L i.e.- what parts are moving and what to check.

 

I believe that if the light goes off, its a transfercase issue, but if the light stays on, and there is no power to the front wheels, it's a solenoid issue or something else

 

You got me thinking more about this problem so I did a little googleing and I came across a few videos that explain what your asking pretty well. They aren't specific to a F150 but they give you an idea of whats going on. The system is to complicated for me to explain in text but basically there is a collar that moves and engages a low or a high gear in the transfer case.

This one is a broad over view of a 4 wheel drive system

This one explains the transfer case and how it works. This is what will help you the most.

This one is a little neater the good part starts at 5:30 and at 5:50 it shows the selector going from high to low.

 

Pontinator I really appreciate your help. I watched the videos you posted and I have a better understanding of what to check. I have another question for you or anyone else who may know the answer: When I shift from 4H to 4L with the brake pedal pressed and stopped, is it normal for something to be spinning in the transfer case or does pressing the brake pedal while stopped supposed to stop everything from spinning while the gears engage?

 

Once again I really don't know but I would say no. I feel like if something was spinning it would be turning the drive shafts. Might post this question to the video and see if someone over there would know.

 

Do you have it neutral before putting it in low four wheel drive in some cases you have to have it in park before switching to 4 low

 

Yes, it's in neutral, brake pedal pressed firmly, not rolling.