I have a '97 4.6L 4x4. I've had a few issues recently and am at wits end.

Symptoms: while pulling a boat at highway speed, the engine engine just died. After waiting about 20 minutes for a buddy to show up with a tow rope, it started up and ran fine...until I got home (10 miles). I parked and after approx 5 minutes of idling it died again. No CEL, and found no codes when scanned. 15 minutes pass, it fires up and works fine.

The next day, I hook the boat up again, dive to the lake, go fishing, drive home. Everything was fine. I unhook the boat and drive to work. Half way there my voltage gauge starts falling and 5 miles later all of my gauges end electric stuff dies. I drive two more miles to work and strange beep starts coming from under the dash on the passenger side (I think). After my 12 hour shift it starts and I start my 10 mile commute. Half way through I lose electrical power again but make it home. Now it doesn't have the juice to turn over.

Are these problems related, and what are the possible causes and cures?

On an unrelated note, what's the easiest way to replace a rear leaf spring shackle?

 

how old is the alternator ? how many miles ? Did the charge light come on ? Im wondering if the alternator is dieing.

 

Its got 235xxx miles, I replaced the alternator in January. And I didn't notice any warning lights when either problems occurred.

 

The first thing I would do is inspect and clean all cable connections
Battery,engine, cab grounds ect

 

It's very easy and inexpensive to obtain an LED monitor to fit a plug on and insert into the dash assessory socket and monitor the voltage performance range.
It tells you immediately what is or is not happening with the charge system and battery voltage.
Your charging is intermittent and running the battery down.
Make little difference what had been replaced and when. You have a problem now, that needs to be addressed.
Good luck.

 

Napa told me my battery was good and The local electric motor shop said the alternator is in perfect shape. I took it to my mechanic and he called said electric motor shop. They told him to basically run a jumper from the plug on the alternator to its positive post. That immediately made the battery take a charge.

As I left work this morning (truck sat approximately 13 hours) my battery was down to 5.9V. after a JumpStart and a ten mile commute it was up to 13.75V.

Does anyone know what's going on?

 

Without knowing which alternator connection was made direct to the battery, what you have is now a drain.
What was done is swap one issue for another.
.
Listen closely, under normal conditions, the alternator does not drain the battery from 'back feed'. However if the diode stack in the alternator has a shorted rectifier it will drain the battery after shut down but still charge it when running.
Where your at now:
1 We don't know what non stock connection was made that could be incorrect.
2. The 175 amp large fuse may now be open. The lead placed above may be going around the fuse, allowing charging.
3. The alternator can still be faulty and not picked up on a test.
4. You need to get to a competent shop for the work because no one is offering you good service, so far. Placing a lead over the outside is asking for more trouble. It's not the way a competent shop works.
.
Remove the lead that was placed.
You need to have the battery fully charged.
The large fuse needs to be checked out.
The alternator needs to be checked for rectifier stack shorts.
The system needs to be fully tested for operation to be sure it works properly.
I'm sorry to report it this way but that's the story as I understand it from your report on your situation.
Good luck.