Is it electrical?

OK so about a month ago I had to replace a
water pump after it went out.  After fixing it,
and diving home I noticed I cracked
transmission to radiator line.  It was bad
enough that on the way home it went into
fail safe mode.  I fixed that.  But now the
speedometer will sometime act weird.  It
will jump around, stop reading or say I'm
going way too fast for what it feels like I'm
going.  It will then run rough after about 30
minutes of driving while the speedo is
doing this.  And before that the
transmission will go into fail safe mode.

If it does this the battery is dead even if I
get to where I'm going an shut it off.  Once I
jump it.  It will drive fine for a few days.  
Sometimes longer than others.  I notice
when it did it this time there was a lot of
moisture in the air this morning.  Usually I'll
be able to get to work before it's done.  
Today I had to tow it home.

Anyways.  Is this electrical?  Did I nick a
wire some where and it shorting out?  I've
replaced the battery.  The alternator works.
The ccheck engine light will come on and
off.  Sometimes it will stay off.  I have no
clue where to look for the problem.  

It has a new fuel filter.  Not even a year old.

It's a 4.3 TBI, 2wd.  If that helps.  Any ideas
would be great.