Shudder/Grinding at start-up

[mfallon]

I've done a bunch of reading on here, but never had cause to post. Well, I guess that has changed...

Recently my Expedition has done something a little disconcerting. Upon turning the ignition, there is a sort of shudder or grinding that is coming from under the floorboards. I turn the key and it is pretty much immediate and last for maybe a second at most. Does anyone know what this may be? It has happened maybe 25% of the time I have started it since I got new tires this weekend. It also seems just fine once started and in gear. Do I have cause for concern?

Thanks for any insights.

 

[tinker1]

My 06' does the same thing. Sounds awful, but lasts only a second or so, and like you describe happens maybe 25% of the starts. I asked a 07' F150 owner if his truck did it, and he reported exactly the same issue. I'd like to know what it is as well.