I noticed the other day that my starter was a little sluggish. and it was a little bit worse the next day. I checked the alternator volts at idle and they were right at 14.6. I didnt have anyone around to bring it off idle for me. today when I was driving into work, i noticed the headlights were a little dim. as i was going down the road, out of nowhere it just kicked down to 2nd gear i believe. i couldnt get it to shift up. I know my batteries are on their last leg and prob wont make it through the winter. but the transmission thing really threw me for a loop. also on the drive to work, i noticed that the voltmeter went from about 13 to less then 12. I dont trust this gauge because it has always read over 16 volts the whole time i have ever owned the truck. I tested it when I first got it and it was at 14.8. Since the headlights were dimming and the tranny kicked out of any type of shift pattern, does this sound like an alternator?

 

Joe, that would be my first guess.

 

Jaoenuzz, i would check the battery terminals and load test both batteries also. if the voltage drops below 11 volts the PCM starts losing some of it`s inputs and the trans will default to second gear.

 

joenuzz,
I can relate to your 'adventure'. This week the alternator went out in my Lexus LS430. I was driving along, then all the dash and indicator lights were flashing erratically, the engine would cut out, then eventually die. A jumper cable 'charge' for a few minutes would get it going normally for a mile or so, then the whole process would repeat itself. The battery was new, so I suspected something more complex was going on. It was confirmed and replaced.
I'm no auto engineer, but it seems that when the battery goes, electronic things get pretty wacky!