I picked up a used "built" 4l80e with 3k stall, forgot who built the trans and what veter it is off the top of my head... supposedly 50 miles on setup, bought it from the owner of a performance shop so I want to give him the benefit of the doubt

wired it into my mustang with PSI's universal harness, everything is wired correctly and reads on hp tuners.

2 issues-

trans shifts through all the gears but wants to stay locked up all the time in all gears, I wired a toggle switch on/off so I can drive the vehicle

also when on the dyno we locked it in 3rd on hp tuners to do a pull but the mph don't match up, seems like it downshifts to 2nd but we don't feel it downshifting. and on a test drive it pulls through 2nd just fine, but when up to speed and I try to hit it, it seems like the trans stalls and doesn't down shift just kind of boggs/cuts in and out

I haven't done any full pulls to get more details, one the motor is new and I don't want to beat on it too hard and im on street tires so it just spins.

only other write up I have seen with a similar lockup issue claimed drilling the feed hole in the pump out fixed his issue..





UPDATE---

Tuner says the pcm is not picking up which gear the trans is in. although under narrow throttle it drives just fine and shifts through all of the gears.

 

sounds like tune issues more then trans/converter issues. is it a segment swap?

 

yes...

 

also seems like the 1-2 shift is quite a bit harsher...

 

Sounds like a tune issue to me as well but i'm not familiar with foxbody conversions really

 

the shifting might be in the tune...having a tuner who knows a lot more than me check it out next week, but the lockup is my main concern right now...

 

the lockup is also controlled in the tune, mine wanted to lock really early as well when I first put mine behind my lq4 in my fox but the ecm still had the stock trans tune in it at the time, after a full tune it was fine and I had my tuner set it to only lock in 4th gear and only above a certain mph and under a certain percent throttle.

 

wont it kill et's/ trap speed without it locking up in every gear over a certain mph?

 

any other input? going back to the tuner on tues, I was more worried about why the stalling/hesitation in third gear while driving it, and why it seemed like it was in second gear when locked w/ hp tuners in 3rd on the dyno

 

TTT any ideas?

 

Sometimes solenoids click and seem like they're working but don't actually work and move fluid.. Rare but it does happen

You should pull the trans connector and start checking and making sure all the solenoids are getting power.. Rule that out first then start fixing the tune..

 

yea going to check resistance for all the sensors next, already checked for power...