On the way to the shop this evening my 99 24v shifted out of overdrive and went to 3rd gear, and would not shift back to overdrive. I was just about to the shop so I passed it off as a fluke as my TPS has been acting up on me.

When I left (at 3AM) I noticed the volts weren't where they were supposed to be and that the truck started out in 3rd gear (limp mode).

I have tach, speedo, & all gauges, and cruise works, but I have no overdrive and no alternator charge.

What gives? Thanks in advance!

 

Any codes? That will help in determining where to go...

 

No codes to speak of.

 

I think you have to address the charging issue, before worrying about a tranny issue,
is it a faulty gauge or is it charging?

 

Not charging.
Why would both stop working at the same time?

 

Does your truck have a Trans control module?? and if so where does it get its power from. i dont do much with auto trans but i am ASE certified

 

Likely the charging issue is CAUSING the tranny shifting issue, like every electronic component the transimission is voltage sensitive, as I said before If you address the charging issue first, I'll bet a bag of donuts your tranny shifting issue will "magically" repair its self

 

Pull the alternator off and have it bench tested by local parts store. Testing on vehicle has been problematic.
There is a large fuse on fuse block directly from alternator. Look at that also.

 

Alternator is good per Autozone.

 

last year my altenator blew and took out the PCM which had my tranny acting funny like you're describing I'd find a way to have that tested, it isn't cheap to replace, i hope it isn't it for your sake

 

So the problem is diagnosed and fixed.. And the answer probably won't really help anyone else if they have this problem, because this kind of stupid crap only happens to me.

The short of it is, the wire that runs from the pcm, to the fuse box to the alternator, that gives a signal to charge, had some "cuts" in it INSIDE the wire loom.. It looked like it was just some wear on the wire's coating.

This in turn shorted out the computer which made it so that the POWER side of the computer no longer activated the positive side of the transmission relay or charging relay, IE no charge. (it also fried that single part of the PCM)

The new PCM I had is from a truck with anti-theft built into it, and those PCM's CANNOT be reflashed for use on another truck.

We basically taped up the damaged wire, then wired the relay to be kicked on by another key-on power-on circuit. Charging & trans works fine now.