4L60e Valve Body - HELP!!!

I just replaced the valve body on my 99 Chevy Suburban (4L60E) with a remanufactured unit. I was getting the P1870 codes and this seemed like an easy way to address the problem. The new valve body was updated with the sonnax fixes, so everything should have worked great, right? Well after it was installed, the truck wouldn't shift into 3rd. In 2nd @ about 3000 rpm, I would start to get a ton of slippage (rpm's up to 4500 but no shift). 1st & 2nd were great, clean fast shifts, but no 3rd (obviously no 4th either). So I pulled the new valve body back out, made sure the check balls were in the right place, checked the solenoids, double checked the bolt locations, installed a new separator plate and gaskets, and put it all back in. Same thing, no 3rd. So I pulled it all back out and put in the old valve body. Now it works like it used to (I have third and fourth) but I am getting a lot of slipping on the shifts. Is it possible I damaged something by running the defective valve body? I don't seem to be getting any slipping except at the shift points. What could be causing the slipping I'm experiencing? Am I missing something obvious here? :banghead: I should mention that I found one of the check balls (1-2 upshift) lodged in the old separator plate before I replaced it.

Well your reman VB is obviously ng, but did it slip before, if not, yes you may have hurt the unit, was the fluid burnt at all. Obviously we cannot look over your shoulder to see if you did something wrong during this entire process, so an accurate diagnosis is tough here.