Hi, new to the forum. Any help with my issue would be appreciated. I have an 07 expedition. Recently a rattling begins at certain RPMs 2000 -3000. The rattling is not isolated to acceleration, but this is where it is the worst. The weird thing is when I switch to 4A the noise goes away completely. I jVe replaced the shift motor on the transfer case and checked for any heat shield rattles. The noise sounds like a bunch of screws in a metal can rhythmically rattling. Any insight? I've kept in 4a as of late due to this issue. Would greatly appreciate some thoughts. Almost sounds like the front axle is half engaged. Thanks in advance.

 

if you think it sounds like front axle shafts are half engaged, it could be a bad integrated wheel end solenoid (IWE). vacuum is applied to each IWE, located on the end of the axle shaft in the knuckle, to keep in 2wd, and releases vacuum to apply/engage front axle shafts for 4x4 operation. if you have a vacuum leak in the lines going to either or both IWE's then there isn't quite enough vacuum to keep front axles from being fully disengaged.