Hi,

I'm in the market for a used F-250.  Yesterday I drove two...a 1999 with 98k
miles...and a 2002 with 58k.

Both exhibited the same odd "feel"  when starting from a dead stop.

Right as you begin to move...there is a "thunk" somewhere in the drive line.
The used car manager at the dealer that had the 2002 said it was "the spider
gear" in the rear axle...and was "normal wear"...   (DON'T YA LOVE IT WHEN
THEY SAY THAT...).

The 98 truck had the same feel...but it was to a greater degree.

Of course...new trucks don't do this...and neither do others that I have
ridden in.

What is your diagnosis of this...and what will it lead to as the years and
miles pile up?  Is there a fix?

Thanks,  Chuck