Subject: Bad Vibes

I'm hoping one or more of you can help diagnose a problem I'm having on
my Eldo.

Here's the main symptom:

When I slightly roll off the gas while cruising at a steady state at
about 55 mph, I feel a shudder or shiver resonate through the frame and
footboards.

What do you think? Carrier bearing? U-joint? Other?

Thanks!

Greg Field