Resizes the solid input shaft sealing rings on the GM 8L90 8-speed after you install them, so each ring seats round and holds line pressure.
This is a three-piece set of input shaft sealing ring resizers for the GM 8L90 eight-speed automatic, the RPO M5U unit behind 2015-up Silverado, Sierra, Tahoe, Yukon, Escalade, Camaro SS, and Corvette. Each piece is a stepped plastic sleeve you push over a freshly installed solid ring to squeeze it back down to its true running diameter.
The solid (one-piece) sealing rings on the input shaft come out of the pack stretched and sitting proud after you slide them into their grooves. Try to drop the pump or drum over a ring that is still oversized and it hangs up, rolls, or gets shaved on the edge of the bore. On the bench that shows up as a cross-leak, a soft or flaring shift, and low line pressure on an otherwise fresh rebuild.
Install the rings starting with the one furthest down the shaft and work outward so you are not fighting rings you already sized. Coat the ring and the resizer bore with assembly gel and clean ATF, then work the matching sleeve over each ring and hold it a few seconds. The ring relaxes back round and clears its bore, so the drum or pump slides on without drag.
The resizers are molded from tough plastic so they will not nick or score the ring surface the way a metal edge can. The kit ships as three pieces to cover the different ring diameters on the 8L90 input shaft.
| Tool type | Input shaft sealing ring resizer / sizer set |
| Pieces | 3 ring resizers (expand and compress) |
| Fits transmission | GM 8L90 8-speed (Chevrolet, GMC, Cadillac) |
| Ring type | Solid one-piece input shaft sealing rings |
| Applications | 2015-up Silverado, Sierra, Tahoe, Yukon, Escalade, Camaro SS, Corvette |
| Material | Tough molded plastic (will not scratch the rings) |
| Item weight | 10.56 oz |
