Th400 behind a lt1

**Magoo_oner** · 03-15-2023

As the title states I have a th400 that I’m thinking of putting behind my 94lt1 that’s swapped into a gbody my question is do ai have to do anything to the ecm to keep the engine running correctly or will not having the pigtail plugged into the trans cause any issues other than fault codes U can always turn those codes off

**dave w** · 03-15-2023

If the current flash is for a the 4L60E, transmission and TCC codes will need to be disabled. The Manual / Automatic "bit" will need to set to Manual.

**Magoo_oner** · 03-16-2023

Ok cool thanks just wanted to confirm and make sure on the engine side everything runs the same

**steveo** · 03-16-2023

you do need a working VSS too, or it'll misbehave a bit, but that's easily solved, and you have no park/neutral logic in manual mode either, so you'll have the same idle tables for park/neutral or in gear. also easily tuned around

**Magoo_oner** · 03-16-2023

Originally Posted by steveo

you do need a working VSS too, or it'll misbehave a bit, but that's easily solved, and you have no park/neutral logic in manual mode either, so you'll have the same idle tables for park/neutral or in gear. also easily tuned around

I think ima give it one more go at attempting to figure out this 4l60e than it worked before I pulled it so idk what’s going on now. I just figured out my idle issue it was a faulty iac not too sure if that had anything to do with the trans shifting out of wack not shifting and tcc not locking up only other thing was the vss wire from my ecm to speedometer wasn’t connected to anything so I think I need to either wire up a speedo or connect switched 12v with a resistor to it any ideas greatly appreciated