10L1000 Transmission Seal Ring Expander and Resizer Kit

This is the seal ring service set for the GM 10L1000, the heavy-duty ten-speed automatic that sits behind the 6.6L Duramax and 6.6L gas V8 in GM 2500 and 3500 trucks. Twelve pieces: expander cones that open the PTFE input shaft sealing rings enough to walk them over the shaft lands without twisting or nicking them, and matching resizer sleeves that squeeze each ring back down to bore diameter once it is seated.

Those two steps are the whole job. PTFE scarf-cut rings take a set when you stretch them, and if you push the shaft into its bore with a ring still oversized you either shear the ring or roll it in the groove. Either way you get a cross leak, low apply pressure on the affected clutch, and a unit that comes back on the hook. Slide the ring up the expander, install it in the groove, then run the resizer sleeve down over it and let it sit a minute before assembly - the ring goes back to size and the shaft drops in by hand.

The tools are 3D printed in rigid PLA and sized specifically to the 10L1000 shaft and bore diameters, so they are not interchangeable with 10L80 or 10R80 tooling. Applications the manufacturer lists include Chevrolet Silverado, Suburban and Tahoe, GMC Sierra and Yukon, and Cadillac Escalade - match by transmission code 10L1000, not by model year, since GM used several ten-speed variants across the same trucks. Manufacturer part number MOTOQUEEN17MUB3.