I know this is being discussed but I didn't want to highjack the other thread. I have a '47 1/2 ton with what I thought was an SM 420. The casting number (590747)shows it's a case for a '31 - 47. A 4X4 site lists the casting number as an SM 420. It has the 'lift lever' for reverse which indicates a crashbox but the Novak's contact said he has seen an SM 420 with the lever. It upshifts fine. Downshifting will grind unless I double clutch.From what I can see it sure looks like an SM 420. Does anyone have pictures of a crash box for a comparison? The more I look into it the more confusing it gets. I suppose the tranny could have been changed at some point. The tranny is in the truck and I can't really get into it due to recent surgery. Any information greatly appreciated. Thanks.
