Fixed. The problem did turn out to be exhaust related. I couldn't find the
exact source of the vibration but after loosening the muffler brackets a
bit the sound has disappeared.

-Mark

On Tue, May 26, 2015 at 10:52 AM, Mark McCulley <markmcculley@gmail.com>
wrote:

> The skid plate and bars are not currently mounted on the van but I'll look
> for other tight clearances that could be vibrating.
>
> -Mark
>
> On Tue, May 26, 2015 at 8:45 AM, Dan N <dn92610@gmail.com> wrote:
>
>> I'd suggest checking the followings
>>
>> -  the engine tubber mounts - those when getting old will let the engine
>> sag down a bit which bring the exhaust pipes closer to the skid plate
>>
>> - the 2 skid plate bars - these could be bent up
>>
>> on mine I have about 3" clearance... on my friend's it's about less than
>> 1"
>>
>
>