10R80 Sealing Ring Resizer and Expander Tool Kit, 7-Piece

The Ford 10R80 and GM 10L80 ten-speed use solid (uncut) sealing rings on the input shaft and clutch drum hubs instead of the old scarf-cut style. A solid ring has to be stretched over the shaft to reach its groove and then shrunk back to size, or it will not let the drum or housing slide on and it will not seal. This kit covers both steps: three expanders to open the rings and four resizers to close them back down.

On the bench: slide the ring onto the expander cone and push it down evenly until it drops into the groove. Do not roll it over the shaft by hand, that is how rings get kinked or stretched out of round. Then run the matching resizer sleeve over the installed ring, lubed with ATF or assembly gel, and leave it in place for a few minutes so the ring closes up. Pull the sleeve and assemble the mating drum or housing right away.

A ring that was installed without being resized, or one that got nicked going on, leaks apply oil from the clutch circuit it feeds. On the 10R80 that commonly shows up as slip or flare on specific shifts, harsh or delayed engagement, and clutch codes after a rebuild. The tools are machined from POM (acetal), which is slick and softer than the rings, so they will not scratch the ring face.