[turbobill]

On passenger car and Chevy light truck applications, other than the torque converter bolt circle diameter of the TH400 and Powerglide being a different diameter (taken care of on the GMC with the two different triangle plates), the diameters of the ring gears were also different.

The car and light Chevy truck Powerglide flex plates used a 153 tooth ring gear and the TH400 used a 168 tooth ring gear. The TH400 flexplate was about an inch greater in diameter. The larger dia. flexplate required the starter be mounted farther away from the crankshaft. In those applications GM used 2 different starter housings on an application that might have each transmission available.

To my knowlege, GMC never moved the starter on any of the light duty applications, so it is likely the flywheel may be the same.