Four resizers and three expanders for installing and sizing the solid sealing rings on Ford 10R80 and GM 10L80 shafts and drums without cutting them.
Slip on one gear after a fresh rebuild, a delayed engagement that was not there before, or clutch codes on a ten-speed that just came back from the bench often trace to one small part: a solid sealing ring that went on kinked or never shrank back to size. This 7-piece kit gives you three expanders to get new uncut rings over the shaft and four resizers to close them back down, for the Ford 10R80 in 2017-up F-150, Expedition, Mustang, Ranger and Explorer and the GM 10L80 in Silverado, Sierra, Tahoe, Suburban, Yukon and Escalade.
On the 10R80 and 10L80, oil for most of the clutches travels through rotating shafts and drum hubs, and each circuit is fenced off from the next by a ring riding in a groove. Transmission Digest describes the 10R80 input shaft as about two feet long, carrying converter, C, D and F clutch oil; its rear rings seal inside the sun gear shaft, and the sun gear shaft's outer rings seal against the CDF cylinder sleeve. These are solid rings rather than the old scarf-cut type. A solid ring has to be stretched to pass over the shaft and then sized back down so it sits flush in its groove. If it is left oversized, the mating drum will not slide on without shaving it. If it is rolled on by hand, it ends up out of round and leaks.
Sonnax lists sealing ring and hub bushing wear among the biggest causes of lost pressure in these units, and recommends air checking each drum with its mating input part, then the whole assembly through the pump before it goes in the case. Air escaping at a ring land means that ring or its bushing is the leak. Transmission Digest adds one trap: when checking C, D or F, no air should come from the tip of the input shaft; if it does, an internal cup plug is missing and new rings alone will not fix it. For the electrical and hydraulic causes to rule out first, see our 10L80 pressure control solenoid guide and the 10R80 common problems and fixes guide.
The kit is listed for the Ford 10R80 and GM 10L80. It is a hand tool kit, so it is not tied to a model year, but ring sizes are specific to the 10-speed family; it is not listed for the 10R60, 10R140 or 10L1000. Check the ID tag on your case to confirm the unit, or send us the year and VIN. Rings, drums and kits for these units are on the 10R80 parts page and the 10L80 parts page.
Have the rings and seals ready before you start: the 10L80 master rebuild kit supplies them, and a case of ULV full synthetic ATF covers assembly lube and the fill.
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They use solid, uncut sealing rings. A solid ring has to be stretched over the shaft and then sized back down, or the mating drum will not slide on and the ring will not seal.
Seven pieces: four sealing ring resizers and three sealing ring expanders, all machined from POM (acetal) plastic.
No. Rotating sealing rings should be replaced on any rebuild. Stretching an old ring off the shaft also distorts it.
Lube the ring and leave the resizer on for a few minutes so the ring closes up, then remove it and assemble the mating part right away.
ATF or assembly gel to lube the rings. Fill a Ford 10R80 with Mercon ULV and a GM 10L80 with Dexron ULV, then run the adaptive relearn.
