- Staff
- #21
Running DEX3 won't hurt it in any way. Actually early 6 speeds got factory filled by ALLISON with TES-389 fluid(DEX 3), and GM simply topped them off with DEX VI on the assembly line(each and every ALLISON is dyno'd before being installed). ALLISON released a bulleting saying until around 05/06 they didn't use seals compatible with DEX VI, but GM said it was fine.