4l60e issues after swap

I finally got my 93 gmc lm7/4l60e swap drivable but I'm having an issue with my trans. I rebuilt it before I installed in into the truck so everything's fine mechanically inside with maybe the exception if a stuck vlv. My trans shifts nice and firm for the 1-2 and 2-3 shifts but will not shift into 4th gear the the convertor licks up fine right at 45-50 mph but not 3-4 shift. If I pull the shifter into the 3rd gear spot then the convertor disengages and wont lickup again. Any ideas what maybe the cause of this other than maybe 4th gear vlv being stuck? Also what effects would increasing my line press in my pcm tune have on the shifting? Would it just shift firmer or will it move the shift points as well? Any ideas or help is greatly appreciated...

Did you re use the stock 93 model trans??

have any adjustments been made to the trans side of the tuning?

the trans is the matching 01 model for the 5.3l and no tuning has been done to the trans yet. a friend of mine that owns a trans shop told me to change the manual lever position switch, any ideas as to how to adjust that thing?

I have no clue, I was asking because I plan on a swap this winter on my 94 model 2 wheel drive and had planned on keeping the original trans

I kinda wonder if it has to do with the tune since it probably has different gears andor tire height.

My guess is that you have the 4th gear servo piston installed backwards. The piston is offset to let it push on the 2-4 servo pin. If this piston gets flipped on the rebuild it will not reach the clip on the pin to engage 4th gear. You should have plenty of room to pull the 4th gear piston/cover off and check this...

Not to jack the thread but I can use my 94 model 4L60e with a late model 5.3?