I have a 2000 Ford SD 4X4 V10. My problem is that when I shift in 4X4 the light goes on and it does spin the fron drive shaft. What it does not di is engage the front hubs.
Now these are new hubs as the others took some abuse with me trying to get them to manual lock. The new hubs worked fine for some time with the auto lock. Now they do not auto lock.

I did read here some time ago the the vacum line may be bad. Where can I look for it. I came up with nothing in search. Perhaps enetering the wrong info for search. Any help would be nice.

Also what repair manual would people suggest.

 

Try out this https://www.ford-trucks.com/forums/6...n-the-fly.html. It covers it pretty well. If that doesn't help come back and we'll try something else.
Joe

 

There is a vacuum line on each side that runs from the back of the knuckle along the brake lines to a connector with a hard vacuum line. These run to the passenger side wher ethere is a solenoid and a pump.

Two ways to check the operation. But you need a vacuum guage.

I start by checking the electronic operation at the point of the hubs. disconnect both vacuum lines at the hubs. Plug one so there is no leak. Attach the vacuum pump to the other. Start the truck and switch it to 4x4. Observe the vacuum pump guage. It should read close to 15 in vacuum for about 30 seconds. When the needle drops turn back to 2wd. The guage should go to about 7 in vacuum for less time, around 15 sec. If it doesn't acheive the desired vacuum then there is a problem in the control side of the system. Stop here, and diagnose back at the solenoid and vacuum pump.

At the vacuum resivoir check for about 15 in of vacuum. Then you can check vacuum to the solenoid, and the output signal to the hubs using a similar procedure as above, but at the solenoid connection.

If the control check was ok, then check the individual hubs. Reconnect the side you had plugged. Then shift to 4x4. Observe the guage connected at the line for the opposite side. If it doesn't acheive close to 15in of vacuum, there is a leak in the hub system that is connected. Then switch the vacuum pump sides and repeat the check. If you find only one side won't acheive vacuum, switch the hubs side to side and repeat the test. If the same side won't hold vacuum, then the wheel bearing system is the leak. If the leak switches sides, then the automatic hub has a leak and will need to be replaced because it is not serviceable.

The wheel bearing assembly has a few seals in it that could be bad. Not much way to tell which one, and should probably service them all.

 

Thak you to both of ya for the replys. I will try the vacum gauge. The other thread has very good ideas and the link to the new lines is great. I have not tried the 4X4 switch and the defroster. Guess I never noticed. Will try this morning.