Strange vibration when driving over small bumb

[Ashgard]

Hi, I have a Ford Transit MK3 from 1998 (a Nugget, camper edition). I recently noticed a vibration when driving over a small bumb. Some more specific information:
- I feel it with my feets when sitting behind the steering wheel or on the couch in the back
- I feel a small vibration, relative high frequent vibration with 2-3 periods.
- I only feel it when the rear wheels pass the bumb, never when the front wheels pass the bumb
- It only vibrates on small bumbs, but not all small bumbs.
- I mostly feel it when driving on the highway
- I dont feel anything strange for larger bumbs

Any suggestions what it can be?

Thanks
Ashgard

[twin wheel camper]

Shock absorber bushes would be my first place to look.
At the rear shock absorbers look at each end and there is a rubber bush this is prone to be becoming loose and will rattle over bumps.

[Ashgard]

I tried to make a photo of the shock absorbers, but it is difficult as there is not so much space. I indicated in red what I think are the bushes, is that correct?

Some more questions?
- how can I inspect this is the issue? Can I feel it by hand?
- anything I can do about it myself?
- if this is the issue, how wise is it to keep driving? We are on holidays, should we go to a garage or can we do it when we are back at home?

Thanks for your advice

[joinerman]

No, bushes are at each end.

[gotgcoalman]

These

bushes.jpg

[rebuilder86]

yep, the little inserts that go inside the round openinngs in the shocks, so that there is no metal on metal contact.
could also be the bushing in the leaf springs, same deal, at each end of the leaf spring assembly.
Also ensure that the U bolts that hold the axle to the leaf springs have not come loose.