I have a 2000 Expedition 4x4, 5.4 L. The 4x4 is the AWD, 4hi, 4lo type. When it is in a load (such as stuck in snow) and in 4lo/hi and you give it much throttle it will make a slipping, well a buzzing/grinding sound from the transfer case. When this happens the 4x4 is not working or the tires are not turning on the front any way. Also this will happen if you really hit the throttle from a dead stop in AWD mode. I had a mechanic friend tell me that it could be the vacuum actuator not working properly or even the fork that it operates may be bent. I have looked around and have not found any one discussing similar problems. Any ideas on this one?

 

donrjuan....got the same damn problem with my 2001 SuperCrew...the picture I get in my mind when I'm trying to use my 4x4 is a broken chain in my transfer case and the sprocket grinding against it....I'm probably going to have to break down and take it to my mechanic atleast for a diagnosis, but the way it sounds it isn't going to be pretty, let me know if you find out anything and I will likewise.

 

Well...got to the source of my problem, the vacuum actuator on the front axel is bad but there was still the grinding metal problem in my transfer case. My brother-in-law and I pulled the transfer case out...broke it down and discovered that the lock-up hub assembly was cracked and half of the teeth were ground off so it would go into 4x4 until you broke traction then it wouldn't work and just sit there and grind in the T-case while your rear tires spin. Not sure which came first the T-case damage or the actuator failing but they are both related as far as timeline is concerned.

Now I just have to track down the parts, this is gonna be fun...NOT.

I will post more once I find the parts and get it back in...

 

That sounds pretty tuff! Thanks for updating us on what you found!

 

T-case is repaired and back in, vacuum actuator (on the front axle) is replaced and she works like a dream now! Thank God (and my brother-in-law, the heavy equipment mechanic). The problems were specifically...the vacuum actuator was rusted inside and would only move the shift rod about half way. Inside the transfer case a part called the "lock-up hub assembly" was cracked and the teeth were ground off (thus the grinding metal noise inside the T-case) and the T-case pump was worn out (and replaced). Hope this helps others with the "4x4 system says it's working but there is a grinding noise in my transfer case and the rear wheels just spin when I'm on a grade" problem. I know it sounds very complicated but it truly wasn't....if you had a set of the Ford service manuals and a moderate mechanical ability you could do the repair yourself...my brother-inlaw is a heavy equipment mechanic but he has never broke down a t-case before and he just used my ford service manual to go through the rebuild process. All together the cost was about $240 for the all of the parts involved in the repair because I did also replace the electric shift motor on the t-case because it was swollen and would have failed this winter anyhow.

Hope this helps man!

 

Many thanks to you! I am going to jump on mine this weekend and see what happens!