How does the 4wd actuate?

[bd1980]

I had something happen on the highway. Going about 70, I hear clicking noise start in the front end, like hubs or something. About 2 seconds a loud BANG that shook the truck very hard...like it was trying to shift into 4wd at 70 mph. What do you think the problem is? Also, it should be noted that it has been extremely cold here lately. Is there something that could have some ice or slush build up underneath that isn't allowing proper engagement? I tried 4wd, it still works good surprisingly. Thanks.

 

[tonydiv]

It sounds like Integrated Wheel Ends. When they don't get enough vacuum or start leaking, they will engage. The vacuum keeps them 'unlocked'.

I've always felt that Ford designed these backwards, since most people have their truck in 2wd 90% of the time.

 

[tojohnso]

I don't know, Tony, I have an '89 Jeep Wrangler and was left stuck on the beach when the vacuum connection failed and 4x4 didn't lock the hubs. I'd prefer failing in capable hubs rather than the other way around for that reason.

BD, not sure but what you describe is interesting. If you get a definitive answer, please let us know!

 

[mindgame]

I'd prefer failing in capable hubs rather than the other way around for that reason.

Amen to that!

 

[bd1980]

Actually I started searching around and IWE problem seems to be mine exactly. Probably a vacuum leak somewhere too. I have an appointment next week at the dealer because I bought an extended warranty. Here is a good link I found explaining how the system works.

Everything You Wanted To Know About The IWE System....And Then Some! - F150online Forums