Little background here, I have an Ls376/480 crate engine installed in my 09 H3 along with a 3200K stall from circle D. I bad the pcm tuned to account for the higher stall and new engine.
The original 4l60e trans broke down within 100 miles (had 100K miles on it and I lost 2nd/4th). I had it rebuilt locally but due to time constraints I had it built to stock level (what parts were available and it was warrantied by the builder). 2K miles later trans broke down due to a excessive slipping in 2nd (band friction material wore down and scarred the drum). This time I had it rebuilt with all upgraded components and added a 0.5 boost valve, billet servo, BW Hi energy frictions, 5 pinion planeteries, wider band, billet rotor, new reverse input drum, 29 element sprag and a sonnax smart shell, new solonoids and a few other components.
Now that all is in, trans is running with two issues. It shifts great up and down and in all driving situations.
My issue is that when the trans locks up in 4th, when it unlocks (with more throttle input) the engine rpms will go up and it will shudder/jolt/stutter like the fuel is cutting out and back in repeatedly and really quickly. If I get more throttle it will shift down to 3rd and the whole problem is gone.
if I hold the trans in 3rd manually and let it lockup (oem program lets me lockup in 3rd) I dont get the same problem when the trans unlocks at more throttle input and the rpms climb normally.
my other problem is that if I have the gear in 2nd and let the rpms climb, once I let off the throttle the truck drops back to 1st (I believe) and then back to 2nd and will keep doing that until I either shift it to 3rd or the rpms drop alot.
My trans builder isnt great help and locally here there arent really good builders. (Im overseas so getting anything from the states will cost alot).

Im hoping someone here can point me in the right direction as its really annoying how incompetent ppl are over here and this is my daily driver.

 

Sounds like it needs a driveability tune. I've done that to my own vehicles and it takes a lot of time, the person who tuned it didn't do that but might be able to fix the problem if you tell them.

 

Well the thing is, after the first rebuild (which failed in 1500 miles) the trans worked perfectly and I didnt have any of those issues for those 1500 miles. It was only after the second rebuild with the upgraded parts that im having those issues.
What Im trying to figure out is that when I shift into OD with the TC unlocked, I can drive forever without issues. But after it locks up, when it unlocks the jolting happens, its as if the trans is confused and locking/unlocking itself many times in a second. If I get off the pedal or give it much less throttle the jolting stops and it locks up again (if i released throttle enough) and the truck drives great again.

 

Whats going on is torque converter clutch chatter. It didn't do it before because the transmission slipped instead. Now that the transmission can hold the torque converter clutch is slipping.

It CANNOT lock up under load without chattering.
The clutch in that TC has no damper springs to absorb chatter and it has a lot of friction material to hold.

It may not do it all the time, theres a spot in the programming that you're hitting thats doing something undesired. For example at 60 mph it 4-3 downshifts at 60% throttle and unlocks the tcc but is set to lock in 3rd at 55 mph. Or something like that.

Theres still a spot in my programming that does weird stuff when I give it more throttle when cruising, I've just learned to set my foot on the brake to unlock the tcc before I accelerate and when I'm back cruising let my foot off.

 

Ok that I understand, but my problems isnt when the tc is locking up, its when its unlocking. I have lockup tuned to lock hard and it feels like a 5th shift but when its unlocking its as if the tc is having trouble unlocking (but in 3rd it has no issues unlocking) and the whole stuttering happens.
Before the last trans build with upgraded parts it only started slipping in the last 50 miles of those 1500 miles...

 

I wonder if perhaps the TCC valve in the valve body or the main TCC solenoid is sticking and causing enough fluid flow to cause the lockup clutch to chatter.

You might be able to solve it by having a tuner max out the TCC Duty Cycle Minimum and Maximum values. This assume the TCC PWM valve wasn't replaced with an On/Off value which might also solve the problem.

 

Well I just got back from a work trip and checked out the TCC duty cycle using my hptuners. The min values are set to 90 and max to 100 all across the tables.
The TCC soenoid is a brand new one that I had installed along with all the remaining solenoids in the last rebuild but I will have the builder check the solenoids.
The truck doesn't show any codes which couldve helped abit...

 

Thats what I said about my car. At some certain speed it unlocks and does something weird, so at that speed I just set my foot on the brake to unlock it before I accelerate.

Your problem is the programming is set to lock through shifts OR it's set to lock in third.
Get rid of third gear lock up and I guarantee the problem will go away. Unless you've got something weird like the lock/unlock is too close.

Would be a tremendous help to see the tune, or at least all the relevant tables.