M22: it’s the magic RPO code for GM’s ultimate musclecar four-speed. Immortalized by street racers and gearheads, it’s known for its brutal gear whine. If you’ve never ridden in an M22-shifted car, pop Two Lane Blacktop into your VCR and turn up the volume when James Taylor rows the gears on the menacing ’55 Chevy. To some, the M22’s “voice” is just plain annoying, but we think it’s pure bliss.
When we needed a tough manual trans to back up the 501hp 455 in our ’65 LeMans project, the legendary M22 came up in conversation. But the law of supply and demand has pushed prices of these rare birds well into the stratosphere, and, truth be told, they still weren’t all that strong. Sure, the M22’s straighter-cut helical gears put less end-to-end stress on the case and gearset, but the Muncie’s weak aluminum case could still flex under load and spit the teeth clean off the gears.
Recently we heard that Auto Gear Company (AGC) had re-engineered the Muncie case to keep the gears lined up even under the most brutal loading. Problem solved. For around $300, we picked up AGC’s stock-appearing Super Case, which features thicker walls for less flex, uses a larger front bearing to absorb more torque, and is cast in higher-quality aluminum. AGC also supplied a beautiful Italian-made reproduction M22 gearset so we wouldn’t have to sift through swap meet junk. And considering this will be seeing nearly 600 lb-ft of Pontiac torque, AGC’s new cast-iron midplate seemed like a worthy upgrade for our bulletproof M22.
Aided by GearZone’s instructional video and builder Ron Worthen’s experienced assembly guidance, here’s how we built the ultimate Muncie—proof that they’re not just for show cars anymore.
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