Our GM SM420 adapter to the Dana 18 / 20 is 4.00 inch in length. The adapter material is 356 T-6 heat treated aluminum alloy, and the adapter has a provision for a transmission mount. Our kit will include a adapter housing, spud shaft with 6 spline for drive gear, mount block, set collar, gaskets, seal, nylon lock nut, fastening hardware and adapter instructions. This adapter assembly will fit any Dana Spicer 18 / 20, Scout version with a 6 tooth female drive gear. The transfer case index to the new adapter will require an index retainer & sealed bearing. Please I.D. the transfer case bore size (3-1/8 inch) small hole or (4 inch) large hole for proper retainer. Additional information can be obtained in our on-line catalog, Jeep & Scout Vehicle Section: Transfer Case Information, Jeeps 1941-79. The kit is designed for exclusive use with the GM SM420 4 speed transmission. The SM420 was used in GM trucks 1947 to 1968 and has a 10 spline output shaft and was used in both 2wd and divorced 4wd applications. Required Options ADV716001 Large Hole Retainer or ADV716002 Small Hole Retainer
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Advance Adapters got its start in Downey, California in 1971 with a single adapter mating a Muncie car 4-speed to a Jeep Dana 18 transfer case. Eventually headers, overdrives, motor mounts and linkage brackets were added to the offerings to complement their core adapter components. When interest in rock crawling spiked in the mid-1990s, Advance Adapters offered low ratio transmission swaps then switched gears into the ultra-low gear transfer case arena. Today, the company is based in Paso Robles, California and their engine and transmission conversions for Jeeps are in kit form and sold as individual components. Shop Advance Adapters Now
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