Shudder before trans rebuild and now am still having shudder after rebuild?

I have a 1999 F250 V10 SD Crew Cab. I just had transmission rebuilt and plugs replaced. I was having a shudder before trans rebuild and now am still having shudder after rebuild, trans shop told me to get a tune-up, I did and now I still have the shudder, it seems to happen around 40-50 miles an hour, I give it gas and it stops. Please Help with this problem. Thank You