Bert LMZ Transmission Kit for 2 Piece Rear Main Seal

The Bert LMZ pairs a 2-speed racing gearbox with a full bellhousing kit for Chevrolet Small Block V8s that use the 2-piece rear main seal, built from 1955 through 1985, aimed at IMCA Stock Car, Modified, Dirt Late Model, and Hobby Stock racers. An internal clutch assembly stands in for a conventional external clutch, trimming rotating weight, and the gear teeth are cut in a dog-tooth pattern meant to shift faster and smoother.

What sets this kit apart

Low gear comes in at 2.40:1, stepping into a direct-drive high gear once the car is up to speed, with neutral and reverse both present. Bert builds the case roughly 2-5/8 inches shorter end to end than a Muncie-style unit, a real difference when chassis space is tight. Torque capacity is rated at 600 lb-ft, with a 1.0625-inch input shaft turning 10 splines and a 1.375-inch output on 27 splines riding the yoke.

What ships in the box

Because this is the kit version, it arrives with a laser-cut, CNC-machined steel bellhousing matched to 2-piece rear main applications, a matching steel drive flange, the bellhousing's own bolt kit, an AN-4 clutch line in braided stainless, and racing transmission fluid, plus the hardware needed to mount it all. A shifter and yoke are left out, so plan on a standard two-lever shifter and matching slip-yoke driveshaft from elsewhere.

Q: Does it need an external clutch? No, the internal clutch assembly takes over that job entirely.

Q: Will it fit a later Small Block Chevy? This kit is sized for the 2-piece rear main seal engines; a later 1-piece seal block calls for the matching kit instead.

Bert's coverage on the LMZ kit runs for one year against defects in materials and workmanship, provided it sees normal racing use and goes in correctly.