Just got a 5.9L swapped into my 3.9L V6 99 1500. I'm continuing to use the 42RE I got rebuilt to go with it as I don't plan to hotdog the truck and eventually plan to get a built 46RE. (This is a Band-Aid fix to hold me over till I get my 408 Stroker done for it)

This is where the issues have begun.

Engine runs fine, my injectors work, some lengthened harness connectors work, etc.

Everything has gone to hell with the transmission. I'm getting a code P0753, among another one I don't remember as this was late last night, this transmission is BRAND NEW, it doesn't make sense for the solenoids to go out right way. I'm running new cooler lines and a new rad as well, didn't want to take any risks. The trans is shifting fine from 1-3 but no overdrive, and my ABS and PARK lamp are now on. I'm leaning towards it being the PCM as I grabbed a 5.9L pcm of a junkyard truck, didn't program it or nothing, I also don't think its off a 2WD truck as I wasn't thinking right at the time. I also just realized I may not have had the kickdown cable spring in the right spot, but I will deal with that later.

The truck feels VERY sluggish in first gear, almost like it's just slip slip slipping, wont shift into overdrive as said before. The shifts from 1-3 do feel VERY smooth however, maybe they're just completely slipping into gear, but they dont have the bang and clunk it did before.

Any insight into this would help, thanks,

 

ABS and such may just be a VIN mismatch. Does your trans temp light come on?

 

trans temp light doesnt come on, but it does when the plug is out, so I know it works, also your probably eright on the mismatch, Im going to order a programmed ecu first before I tear into anything.

Edit

Thought id mention to you it did blow a coolant hose (didnt overheat), and a cooler line leaks, threads on the new rad were terrible.

 

Okay, Ive formed an idea. So when I wired in the injectors for 7 and 8 had to replace the connector because it kind of just fell apart. So there's a good possibility that those pin outs I wired them wrong, so I think if I get a new ECU and a new connector for that. And redo it all and make sure double check triple check. It's all wired correctly, it should be okay. And my a b s and brake light should go out with a vin correct ecu.
As you can see the overdrive and lockup pins are infact located in this pcm connector, along with the vehicle speed pin which I know has something to do with the brakes and abs stuff.

 

Update : believe it to be the transmission solenoids.

Replaced the plug, reinstalled the V6 ecm, same code, only p0753, I think it was a short to ground? Did the diagnostic chart, found no short within the wiring or my plug, but Im getting no ohms between the governer solenoid and overdrive solenoid. Also realized the sluggishness is because the torque converter lockup isnt functioning. More testing is required for my wiring as I didnt do from the pcm plug to trans plug, but still, I do believe its the trans now, its almost like they didnt hook those up or perhaps the solenoids just arent good.

Going to call and make sure this doesnt void my warranty on the trans before dropping the pan and replacing those solenoids.

 

If you have a warranty on the trans, why are YOU replacing parts??

 

In all honesty the 5.9 swap was something I did after I had sent the 42re off to be rebuilt, the poor 3.9 that was in the truck was on its way out and had been abused its whole life until I got ahold of it, and I decided if I'm going to Band-Aid fix it I want to replace the engine, and do the electrical for a more powerful V8 I eventually plan to put in.

I'm afraid they would void the warranty entirely if they found out the truck isn't running a 3.9L but rather a much more powerful (this is questionable) 5.9L. Either way, I can honestly say it's not MY work that has failed, it's THEIR work unfortunately. Even though I've followed their guidelines, flush or in my case replace the trans cooler and trans cooler lines before installation.