700r4 taking forever to shift out of 1st gear

[ccrane0044]

Hi guys, I'm having some transmission issues and I'm stumped. Ive been building my truck over the past few years and finally got it on the road. A few years ago I bought a Performance Automatic trans through summit racing. It lasted about 2 weeks before I blew up the torque converter (I'm assuming it's because I bought a cheap Converter). I pulled the pan and everything inside looked ok so I'm hoping theres isn't any further damage. I replaced the TC with one custom built by a local builder who has a really good reputation. And now for the issue! Since putting in the new TC, and hooking everything up it doesn't want to shift out of first. At first it wouldn't budge unless I was just under 5000rpm regardless of how fast or slow I tried to accelerate. I tried readjusting the TV cable and I got a bit better, would shift at 3500 rpm but no sooner even if I tried shifting manually. So then I tried disconnecting the TV cable all together and still holds until 3500 rpm before shifting. What could be causing this? Any help would be appreciated.