No lock up in OD

[JOSH13]

I have an 01 Z28 which I just had my 4l60e and stall rebuilt in and since I put it back in the car I can't get it to lock up in OD .... Could this possibly be a VCM related problem ? I had already tuned the vehicle for this stall before and it ran just fine. It is shifting into OD but it isn't locking up. I have 2.73 gears and previously when it locked I would be doing 80 mph at 2,000 RPM's now at 2,000 RPM's it is doing 60 mph so it definitly is not locking up.
Any advice on this problem would be appreciated
Thanks

[PitchblackC3]

scan your cylinder misfire counts while driving. If you see a lot of misfires, that will keep the TCC from locking.
I had that same problem after installing a stall converter. Had to slightly decrease the knock sensor settings.