I had another thread with these issues, but I've narrowed many of them down so I wanted to hear fresh opinions. Truck has excellent reverse, while in drive it's stuck in what seems to be 2nd. Can't pull it down manually into first, can't command 1st with tuning software, does not upshift either.

2007.5 NNBS (separate ecm and tcm) 3.23 rear
2003 GM Goodwrench 80e, Circle D "budget" 3200, Trango HD2

First I followed these directions to a T to install and wire - 4L60E to 4L80E conversion in a GMT900

Here is everything I've done to try and diagnose:

- Sent TCM to someone who had a functioning 80e in their GMT900, TCM tested fine. Worked flawlessly in their truck.

- I tested that the trans was getting power by putting a test light to pin E on the trans connector.

- Bought a Tuned by Frost trans adapter harness and pinned the trans connector and tcm back to stock. This got rid of the "U0073" DTC I was dreading, but still no difference.

- Had the factory trans file loaded back in, as the Express C2500 trans file is not needed with the Frost harness.

- I drained the fluid, dropped the pan, and tonight tested the solenoids. I applied power and they click, and they have between 20-30 ohms resistance like some tutorials said they should.



I'm beyond done scratching my head and getting nowhere. I can only think of a couple more things to try.

- Anyone know where to probe to test to make sure I'm getting power THROUGH the plug?

- Would the force motor (I think that's what it is called) cause these symptoms? Is there a way to check?

- Would misplaced or missing check ***** cause this? I used 7 (of 8) per the HD2 instructions, but there is a chance they may not have stayed where they were supposed to.

I know some people on here are damn smart, thanks in advance.

 

I had the same thing on my 06 but I used an adapter harness so I didn't have to repin...turns out that harness will plug onto the trans two ways not just one like the oem, I unplugged and rotated the plug 180, so now the part of the plug that was on "top" was on the "bottom". I'm sure its electrical, reverse and second don't use the shift solenoids, so if you unplugged the harness all together you would still have rev and 2nd.

 

Pin "E" will should have power. LsF-150 is correct, you will still have reverse and 2nd with the harness unplugged.

 

Damn, are you serious about the harness going on both ways? Why in the world would it be like that?

I'm more than reassured that it is something electrical, I think before I put it back together again that I'm going to do more probing with a test light on the inside and write down what wires have power keyed on and off.

 

Update**

Just got out from underneath the truck.

With a test light and keyed on power:

I DO NOT have power to any of the 3 wires going to the manifold pressure switch.


I also do not have keyed on power to either of the two wires going to the EPC solenoid.


Are these supposed to be getting 12v with the key on?

Also, I checked every single fuse under the hood, regardless if it was even remotely related to the transmission and every fuse was good. While testing with the key forward, I got back in the truck and noticed my DIC flashing "engine hot, a/c off" and "reduced engine power". Stupid truck.

Also, I'm not sure which harness the above posters were talking about, but with this Frost harness there is definitely only one way the connector goes together both where it plugs into the factory transmission connector, and where it plugs into the transmission.

 

The manifold pressure switch grounds certain wires throught the transmission, depending on shifter position. But the transmission must be running to create the pressure for the switch. And the EPC has it's own 2 wires going to the PCM independently.

 

So, if I understood correctly, the pressure manifold grounds wires but doesn't do a damn thing until it goes into gear and creates pressure, therefore no power just in a keyed on state.

The EPC wires go to the pcm, the pcm just sends it signals, but it also would not have 12v with key on not running.

I read other people with conversions, and original transmissions, replacing solenoid B and ridding themselves of similar problems that I'm having. I guess I get to throw more money at it blindly.

 

Same problem in my 01. Just got truck back from trans shop and they said not the tranny. Good thing for me but frustrating. We are in the process of just getting my segment swap back to try it without the relay mod. But the strange thing is the relay mod shifted for about a yr n half.

Everyone is stomped just like your situation. I'm just throwing this out there but I believe it's a TSB about a ignition problem. That feeds the tranny power on different wires b4 the key is even turned. As soon as its inserted power should be at the tranny to self diagnose.

I'm planin to try that if all else fails after the segment swap. Literally I've been checked every thing just like you. And redid about everything

 

Let me know if you get yours figured out and what it ended up being.

I have a wiring diagram, I guess next step is to unplug the tcm and probe each wire with 12v and see if it makes it down the wire to the trans connector.