My truck made this noise when I pulled my fifth wheel & now it did it again pulling my 2 place snowmobile trailer with 2 sleds, about 75 mph it clunks every once in a while so I slowed down to 65 mph didnt really do it then, the passenger side hub acculator or iassume it was replaced that ring around the outside of hub with tubes hooked to it.. is the other one bad or is it my hub assembly it self truck has 165,000 miles & driving it every day to work it dont make noise, only when i hook a trailer to it, 4 wheel drive seems to work also ???

 

Probably the vacuum line check valves are going bad. Could also be a system leak in the IWEs or vacuum reservoir.

 

here we go again

no offence-- lots of info on here about poor vaccuum to the IWEs

start by putting a vaccuum hand pump with a gauge on the vaccuum line by the IWE valve (on the engine) side you will need a "t" fitting and a short peice of 5/16 vaccum tubing.
start eng. and run for about a min, shut off eng. it should hold vaccumm if not you have a leak. it could be bad check valves or a line. use hand pump to pull vaccumm on each line (there are 2 "t"s at the IWE valve) i have found leaks in the hard plastic vaccum lines the most and have found a leak in the plastic line behind the battery going into the plastic vaccum can on 5 trucks.

the check valves and vaccuum can help hold a steady vaccuum during eng speed changes, this would account for the problem happening at different times under different driving conditions.

happy hunting

 

Yeah I know started reading info after I posted this topic , but I got on the high way today with a good head wind at 85 mph it makes the noise, I dont know i it is the hubs its something loose like the hood or grill smacking, it kind oflifted up in the wind, when a good side wind hit it ratteled whatever is loose & it made the noise, the passenger side acculator ring was replaced, I will try & tighten things down & see if it works well...

 

Wind related it could be your mirrors or the bumpers for your hood located in the lower opening in front of the radiator might need to be adjusted.

 

I made this thread to help diagnose 4x4 problems: http://www.f150forum.com/f72/how-dia...m-esof-186872/