Shuddering.

[tortoise]

I recently purchased a 2000 ford expedition xlt with the 5.4 I have a strange shuddering/grinding noise that you can feel through the floor board when excelrating.
The transmission has been tested and is fine the feeling originates in the front end under the floor board or a little further forward.

 

[Johnathan M]

Could be your integrated wheel ends (IWE). There's a solenoid which controls vacuum to the wheel ends to keep the hubs unlocked. If your vacuum is weak they will be trying to engage but not quite engaging. You could try unplugging the vacuum line off of that solenoid (which will release the vacuum to the hubs and allow them to fully engage) and then unplug the electrical connector on the solenoid so you don't end up with a vacuum leak where it's unplugged. On my 2013, the solenoid is on the firewall over in the driver side corner under the hood. I'm assuming the 2000 operates the same way, but I'm not 100% sure on that