I think they are making running changes to the B4/T4 IMHO. If you look at the packaging of the Rear arms, they are now B44/B4 Rear arms. Same goes for the rear hubs the B44 and B4.
Rear Hubs
http://www3.towerhobbies.com/cgi-bin...?&I=LXSZC4&P=7
Rear Arms
http://www3.towerhobbies.com/cgi-bin...?&I=LXSYZ9&P=7
Rear CVA Axle
http://www3.towerhobbies.com/cgi-bin...?&I=LXSYZ6&P=7