Should I just buy a built torque covertor or built TC and trans...and what brand/kind?

So here is my problem. I have a stock trans and torque covertor. Its starting shift kind of rough and when it gets hot from driving a while it starts to feel like your slighly pressing a clutch in when pulling out from a dead stop (slipping) and starts to feel like there is play if you brake then accelerate (like something is slideing forward then backwards.

It is a 03 silverado 2500hd, 4wd, automatic. Efi live (5 tunes; 150 and 80hp are my most used) 4" straight exhaust, afe cold air, ppe boost valve. 200k miles.

 

You could get a built torque convertor, i think that may be one of the reasons for the trans. slipping.
You should also think about upgrading your valve body.
I had a triple disc and heavy duty valve body put in my truck last year and it shifts better than before. As for good companies out there, there are a lot of good ones. Mine is from source automotive near Portland Oregon.
Hope this helps.

 

for starters, you should look into changing the transmission fluid and filter. this may help a lot