Automatic Transmission - Late 1-2 shift part throttle

Hi, I just rebuilt my own 4l60e transmission and put it in with my freshly rebuilt motor. It has 3000 midwest converter but it is a pretty loose converter.

So i did my first startup and all that fun stuff, then i took it around the block. The 1-2 shift is really late like 3500-4000 Rpm but the shift feels normal and good when it does. All the other gears work great and normal.

It feels like its being commanded late.

Im gonna scan it(hptuners) later today see if i find anything.

Any ideas?

Shifts are commanded by RPM and MPH. I would suggest letting RPM determine the shift, then set the corresponding MPH about 3-4 lower than that.

I lied i dont have 2nd gear, It goes from 1 to 3. It does have 4th gear so im going to look into the 1-2 servo piston seal and some other stuff.

Shifts are commanded by RPM and MPH. I would suggest letting RPM determine the shift, then set the corresponding MPH about 3-4 lower than that.

That is only true for WOT shifts; I think pajamasam was referring to partial throttle shifts.
Partial throttle shifts are commanded only by mph. There is a tunable value that determines what percentage (%) of throttle is considered WOT after which shifts occur when BOTH the tuned RPM and MPH are exceeded.
(Sorry, not trying to correct anyone.)

I lied i dont have 2nd gear, It goes from 1 to 3. It does have 4th gear so im going to look into the 1-2 servo piston seal and some other stuff.

Are you sure you are shifting from 1 directly to 3?
And are not just experiencing a loose converter?

I'm no trans expert, but if it really is shifting from 1 to 3, this sounds more like a shift solenoid problem. If the 1-2 servo wasn't working, I think (but not sure) that you would have a terrible flare after shifting out of 1.
(Again, they is way out of my experience level.)

FIX:1-2 shift servo piston had a cut ring, replaced and works great.

onto the next problem.