Possible alternator issue???

I have a 2002 Jimmy SLS. It only has 96k on it. I went out last night to do some running around and the truck wouldn't start. I had a friend come over and boost it for me and it worked fine after that. I drove around for about an hour and a half to let the alternator recharge the battery, and it did, but when I went out this morning to start it it barely turned over. I let it run after it started for about 4 minutes, then turned on the radio and it put it in drive. It immediately lost power and almost stalled until I put it in park and shut it off. I started it again and it worked fine after that. I took the battery in to get it tested and it came out fine. Could this possibly be an alternator issue? Any help would be appreciated.

Yes - after 60-80k most are shot. Most auto stores test for free (load test ) in vehicle but your gauge should be close to 14v when running (13.6). Make sure the battery is really good (not just a surface charge and at 12.6 volts) and if in a hot climate 3 years is standard life - really.

Also make a careful inspection of the wires/cables running from your battery's hot post and ground post. You could have corrosion or a frayed cable end at a terminal or it's possible a critter holed up in the engine compartment long enough last winter to chew into the insulation and cause a short. This is something I've had to fix twice on the wife's vehicles over the years.