Description: Pontiac M-21 Heavy Duty Muncie as Specified by Pontiac Motor Division. This was a Developmental Item that was created Specifically for the Heavy Hitting 428 High Output Cars that were ordered with 3:73 and up Rear Differential Ratios. The reason they basically created a Munice M-22 Long Shaft Transmission was because they would quite destructively rip themselves right off the Bellhousing or Explode in half.
