There are significant changes on the Workmaster 45 & 55 vs the TTA series. The transmission changed from an 8x2 to a 8x8 w/synchro shuttle. Also the rear axle is now an inboard planetary (same rear axle as Boomer 8N) vs the outboard planetary on the TTA. The engine is now a 4 cylinder ISM vs the 3 cylinder IVECO in the TTA.