Transynd vs Dexron VI

Allison ONLY recommends transmission fluid that is TES-295 approved. Several manufacturers meet this spec. I would not use any fluid that does not say that it meets the Allison TES-295 specifications. The older transmissions did come with a non-295 Fluid, probably Dex III in your case, but why go with any inferior fluid when Allison now recommends a fluid that meets TES-295 in their older transmissions. You do not have to buy Allison fluid if you don't want to give them the money but I would definitely recommend buying the newer spec fluid from someone, anyone, instead of using an older fluid. Saving a few bucks on a transmission that can cost $5000+ to repair just doesn't make sense. BP, Castrol, and others make the TES-295 fluid that you need. Try to find one on sale and use the right, most recent fluid, instead of using a fluid that Allison abandoned many years ago for their transmissions.